Entrapped Air
 

The components you listed should have no problem keeping your engine running at the correct operating temperature. I suspect either blockage or air trapped in the cylinder heads (perhaps elsewhere). If the coolant tank is below any other part of the cooling system (radiator, cylinder heads, etc.) you will not be able to adequately fill the cooling system because the entry point is lower than the highest point in the system. I'll exaggerate to make my point - suppose your coolant tank was located just above the starter. You remove the pressure cap and try to add coolant. How are you going to make the coolant reach areas HIGHER than the coolant tank opening?

If this is the case, try filling through the upper radiator hose.

Thanks for the insight, but yes I have drained and filled.

I always make sure to fill on flat, level ground through the expansion tank. With everything located in the stock position, this should be the highest point.

This is a DA question;
Did you replace the head gasket and some how install it backwards and cover the water outlets?

I have owned the car for only 3 weeks and the rebuild was in 2001, so I have no clue. I can't imagine that's the case, but I guess you never know.

Does your bill of materials on the engine build mention anything peculiar about the engine gaskets? Specifically the head gaskets?

Just curious.

All it says is that it has a Fel-Pro full gasket set and it has a thickness of 0.041 in.

Here are a couple sheets from the build:
http://s8.postimg.org/3umb6sgjp/engine_build_1.jpg
http://s24.postimg.org/efwe3fb79/engine_build_2.jpg

That would be their PermaTorque gasket and it cannot be installed backwards so don't worry about it:cheers:

Jim

To avoid Air being trapped you need to have the exit point of the coolant higher than any other part of the engine, On this old Corvette that would be at the Thermostat housing. The Corvette should be parked with the front wheels higher than the rear, even if this means jacking it up or putting the front wheels on blocks.
Fill from the Thermostat housing, yes I know this means it has to be unbolted from the manifold. Fel Pro makes a Perma Dry plus gasket for the thermostat that is re useable and does not need any sealant.
Part # 35562T it uses a solid body with rubberized silicone so it seals more like modern gaskets. ( Will not pass judging if this car is NCRS points car ) This does allow you to quickly remove the two bolts lift up the thermostat, check your fluid level and re install with no clean up or wasted time.
If your fluid level is not at the thermostat when you open it up you have trapped air. The location of the Corvette overflow tank is a cause of trapped air because it is located low in the fender, you can't fill a Corvette completely from the coolant tank. You do not have to drain and refill, just open the thermostat and burp any trapped air and re fill directly into the thermostat housing hole, thermostat removed, with the car parked front end up. Most driveways have enough grade to do this.
This is not new science, modern cars have burp valves positioned at the highest point to get air out of the systems, some have multiple burp points. You could always drill and tap a burp valve into the top of the thermostat housing, it would sure make this job easy. ( would not please the points judge ).
When you fill the block do it where it is quiet and listen as you fill, you will hear air escaping, stop frequently and let the air escape before continuing your fill to avoid trapping air in the system.
Hope this helps.

"So I got that going for me, which is nice." - BM

Thanks for the tip. I'll follow this procedure.

You may have already done this and have a full engine but it sure won't hurt to know. I really hope you get it running so you can start to drive and enjoy. ( the dirty secret is many on this forum enjoy the tinkering it takes to keep one of these old machines running otherwise we could just buy a new car and turn the key ):cool:

I'm happy to join that club. Despite this frustration I dont miss my Lotus Elise at all, even though it was as reliable as I could ever ask.

This is a popular notion but I've never found this to be true. I've always filled them from the oflo tank. C-2,3.

You can bleed off any trapped air by loosening the thermostat housing.:thumbs:

I think loosening the T stat housing is another way of skinning the same horse, should work just fine. Watch the escaping air till you get fluid with no air bubbles and your good to go. I like that re useable gasket for this type work. It saves tearing a Paper or fiber design or needing sealer. I replaced the water pump on my wifes 530i Straight 6 cyl, it had a purge at the front of the engine and another on the top of the radiator, made it very easy to purge the air. I fill them carefully and was surprised how much air was still trapped on start up.

After reading 117 posts and trying to diagnose this problem yourself , you haven't got it fixed .
I think it is time to take the car to a professional mechanic .

Bill

I prefer the Mr Gasket gasket on the bottom. I don't understand why Felpro makes these blue gaskets for chevys. Now Ford I can understand.

http://www.jegs.com/images/photos/300/375/375-2202.jpg

http://a248.e.akamai.net/origin-cdn....RG-738-G-2.jpg

Thin cylinder walls(from excessive overbore ) or insufficient piston to wall clearance will make an engine heat like this.

The head piston Engineer for Sealed Power built a 496 for his pickup back in 2001, he tows his 70 Buick to the race track with the pickup, the pickup will run a high 13 second qtr mile with this new 496.
His Piston to wall clearance is .0009, under one thou clearance.
He built this engine with Hypereutectics not forged but it works, to tow and to race when he wants to. He did this because he knows it works in a perfect engine.
Modern manufacturing of engines has piston installs of .0006 in production engines with Hyper pistons and skirt coatings.

After reading through the thread.. First to everyone that thinks the stock pumps that you can buy over the counter are just as good as the old pumps haven't taken the back off them.. The cast impeller moved water.. the stamped ones that you see now don't do as good as a job.

I don't think it's a pump problem regardless if it's a high flow pump. I have a Stewarts Stage II pump and it keeps the car cooled even on the hottest days.

I do agree that someone else should take a look at the car and you have one hell of a engine guy in your backyard there in Denver. He's here on the forum and his name is Lars.

Hitch

I'm thinking you're right.

What's the best way to get ahold of Lars? His PM box is full.

I've been following...and maybe I missed something...but have you removed the radiator and had it checked by a radiator shop to verify the condition?

Frank

Here is a rough diagram of how the radiator is functioning. Inlet and outlet temps are from the hose and all temps are in deg F.

http://s11.postimg.org/3z6ygud03/Untitled.jpg

First, didn't closely read all the previous posts, and I am sure there is much good info there along with some common wisdom that may or may not be correct. Second I had this exact same problem for years after trying almost everything I or anyone else could think to try. No matter what the car would definitely overheat and not just a gauge reading issue but puking steaming eventually spun bearing overheating. My problem was on the freeway at speed. Temps would just climb apparently without limit.....

Some details that might have made my problem worse is that I live in SoCal and I drove the car in desert temps often over 90-100 degrees. My car had 4:11 rear gears so it was spinning fast 3500+ on the freeway.

After all cooling issues anyone could find and some that were just suspected were addressed the car would still get hot. What turned out to help was really strange but I still hold that it was a major factor, I replaced the suspension. I know weird but my theory goes that at speed the soft springs allowed the car to nose up (clearly visible) and in this position air didn't flow well through the radiator....

No matter how good the cooling system, even if all the parts are in perfect working order, bad air flow will mean you can't get rid of enough heat fast enough to keep the motor cool. Why didn't the fan pull in enough air, how can this somewhat common nose up condition not cause this problem more I have no clue. I can not say conclusively that this was the total cause of my problem but the problem was much diminished after the suspension make-over. To this day the car still runs hotter than I would like (however it is now no longer stock and has a hotter modified engine) and will sometimes spill a little fluid on a hot day but it is at least enjoyable. After years of conditioning, I still keep an eye on that gauge.

Have read all. There was a post to test face of radiator for warm and cooler spots. With a cross flow I would suppect that the #s L to R would be much closer from top of the core to the bottom. My thinking is the one that is showing a 54 degree drop is plugged and so the water sits there while more and more air flows over that tube. And yes I am aware that you still see a total of 20 degrees drop. Mel

Only a 15* delta from the inlet to the outlet says pretty clearly that the radiator isn't doing its job; that should be at least 30*. :thumbs:

It's not like he wasn't told that a'ready.

:thumbs:

Agreed. Now that all the cheap options are checked off, it's time to call DeWitts.
I also hope to get ahold of Lars and get his input. It would great to pick his brain.

Yeah, when you chose to call on someone outside of what you'd already been told, I just ignored this thread from then on. Sounds disrepectful to me to go to an outsider after you didn't bother to check out what you'd been told by those trying to help you here.

Who is Lars and what does he do different than anyone else?

Lars used to post here a lot and provided a lot of good information but doesn't post here very often anymore. I mentioned him as he lives in Denver as does the OP and Lars helps lots of Corvette owners out. :cheers:

Sorry mike but I don't know who I choose to ignore. My path towards a solution was one step at a time and I left the radiator for last since it's the most expensive. Makes sense, right?

Lars is not an outsider but a knowledgeable forum member that wrote a few articles that were helpful to me. He has a reputation for helping forum members just as you have been so kind to do.

Mike doesn't help anyone, he just likes to stir the pot with his "imagined expertise". Don't worry about it. Your best bet is to put him on your ignore list. Unfortunately, when someone quotes him, it shows up in that post. Otherwise, he would completely invisible which suits everyone just fine. Lars has probably forgotten more than MikeM will ever know. Put him on your ignore list and life will be much improved.:cheers:

Jim

WOW.. just thought it was me...

Hitch...

Lars
 

Had a great day when Lars came to So. Cal and showed his skills. Guy was there with a C-3 that he bought a few weeks prior and it had been "tuned" by the dealer. New cap/wires etc. Total init and cent was 6 degrees. Lars tore down, cleaned, shimed and lubed the dist. Guy took it for a drive and was goofy happy when he came back.
Like the Monkies--Now I'm A believer. Mel

Oh yeah I met him almost ten years ago when the "Tuning for Beer" tour came through Washington, DC..

Here is a pic with my pop, Lars and I talking behind my 66.. I wish Lars would post more in this section again...

http://img.photobucket.com/albums/v1...eftfront-1.jpg

Hitch

Had a same problem on my 64 327, had a friend over to help me trouble shoot it and he discovered that the the hose was sucking together and making a water flow blockage under higher revs. The hose looked great a little soft but when I took both hoses off the wire inside both the hose rusted out allowing it to suck together under high revs. I use only ribbed hoses now. Hope its that simple nothing worst is to have a vette you can't drive.

I have to agree with Mike on this, he takes the time to reply (essentially with the correct direction it would seem from his earlier post) and is not acknowledged.
That happens all too often, and as a result many who used to post don't anymore. I guess when you throw your hat in the ring, that's the chance you take. Some may not like his brand of humor, but he does know his stuff. :smash:

tebok,

I went with the Dewitts SP020.

http://www.dewitts.com/products/1963...bo-restoration

My car never gets above 180 degrees and I am running a 383 stroker with almost 11:1 compression and ~450hp. Absolutely no issues. I also removed my shroud and fan as a personal choice...I still have the shroud and fan in a box. However, the good thing about this Dewitts combination is that you can retain the shroud and stock fan even with the electric fan assembly if you prefer.

Its expensive but this will make your car useable and time of day/weather temps will be irrelevant. Drive and enjoy!!

Best,

Frank

oh, and Lars is one of those rare guys who in my mind is a car guru...the reason his name came up was the connection to the carb and vac advance discussion as it was related the overheating issue. If anyone could figure out that piece, Lars is the guy. He's helped me before with high elevation tuning issues while I lived in Colorado Springs...he's a first rate car guy.

Cheers,

Frank

Great suggestion Frank. That's the top on my list. I would be ecstatic if I could fix this solution for less than a grand.

Does anyone else want to chime in on what radiator they prefer?

If a radiator is next on your list I would buy a stock OEM Dewitts.

NOW, having said that before you spend $800 have you contacted Griffin about your current radiator? It's unusual that a 6 year old radiator of this quality is bad.

Dewitts
 

I live in central Florida. I have installed a Dewitt radiator in my 66 and 68 coupes. My 66 is black on black with a Vintage Air system. Both cars runs 180 degrees day and night in the dead of summer. A cooler engine also allows the A/C system to work more efficiently. Good luck. Jerry

Thanks for the input.

It turns out I read the documents wrong and the Griffin is actually 16 years old.

I am very happy with my Direct Fit Dewitt.

At 16 years old I would not feel too bad to change out your radiator.

For the 427 small block build in my '61, I used the Dewitt OEM style replacement, as it seemed to have the most BTU exchange capacity of the radiators they offered for my model year.. It cost more, but capacity was more important than price. Plus, that rad looks stock.

Well that puts a whole new twist on this overheating problem, if it were me I would be buying a new Dewitt radiator.

But hey it's easy for me to sit at my desk and spend other peoples money. :D

I would hope that if you choose to buy a new radiator, you post the results.

Don't worry buddy, I'll keep posting updates as they come in. I'm on a project site visit this week, so there's some delay, but next week it's on

I would try first a new cap on expansion tank ,when overheating happends air gets into system and temp rises .also timing is important along with vacume advance I have a 63
300 hp that did the same thing if you look at the early carbs they only have one port to the advance mine is automatic and is shared with the air tube to the trans.Thease eary cars were set up to run cooler with the advanced hooked up .call Dewitts they can help with this .you dont need all that other stuff no flex fans special coolent the stock fan and cluck shoul work fine if set up correctily .What I dont understand why its overheating while running fast ,This tells me timing or vacume look at hoses make sure not backwards .

I just got my dewitts yesterday afternoon and have it mostly installed in my 57, I had them paint it and it took a few weeks to get here. The delay could be that I ordered it through Corvette America and with a Holiday in there too. This is just a heads up you might want to place your order sooner than later.

Two guesses:

Didn't read the previous posts
Sent from phone

:lurk:
No guess here where I got that
This was written by a former GM engineer as a response to a similar question on a Camaro board:


As many of you are aware, timing and vacuum advance is one of my favorite subjects, as I was involved in the development of some of those systems in my GM days and I understand it. Many people don't, as there has been very little written about it anywhere that makes sense, and as a result, a lot of folks are under the misunderstanding that vacuum advance somehow compromises performance. Nothing could be further from the truth. I finally sat down the other day and wrote up a primer on the subject, with the objective of helping more folks to understand vacuum advance and how it works together with initial timing and centrifugal advance to optimize all-around operation and performance. I have this as a Word document if anyone wants it sent to them - I've cut-and-pasted it here; it's long, but hopefully it's also informative.

TIMING AND VACUUM ADVANCE 101

The most important concept to understand is that lean mixtures, such as at idle and steady highway cruise, take longer to burn than rich mixtures; idle in particular, as idle mixture is affected by exhaust gas dilution. This requires that lean mixtures have "the fire lit" earlier in the compression cycle (spark timing advanced), allowing more burn time so that peak cylinder pressure is reached just after TDC for peak efficiency and reduced exhaust gas temperature (wasted combustion energy). Rich mixtures, on the other hand, burn faster than lean mixtures, so they need to have "the fire lit" later in the compression cycle (spark timing retarded slightly) so maximum cylinder pressure is still achieved at the same point after TDC as with the lean mixture, for maximum efficiency.

The centrifugal advance system in a distributor advances spark timing purely as a function of engine rpm (irrespective of engine load or operating conditions), with the amount of advance and the rate at which it comes in determined by the weights and springs on top of the autocam mechanism. The amount of advance added by the distributor, combined with initial static timing, is "total timing" (i.e., the 34-36 degrees at high rpm that most SBC's like). Vacuum advance has absolutely nothing to do with total timing or performance, as when the throttle is opened, manifold vacuum drops essentially to zero, and the vacuum advance drops out entirely; it has no part in the "total timing" equation.

At idle, the engine needs additional spark advance in order to fire that lean, diluted mixture earlier in order to develop maximum cylinder pressure at the proper point, so the vacuum advance can (connected to manifold vacuum, not "ported" vacuum - more on that aberration later) is activated by the high manifold vacuum, and adds about 15 degrees of spark advance, on top of the initial static timing setting (i.e., if your static timing is at 10 degrees, at idle it's actually around 25 degrees with the vacuum advance connected). The same thing occurs at steady-state highway cruise; the mixture is lean, takes longer to burn, the load on the engine is low, the manifold vacuum is high, so the vacuum advance is again deployed, and if you had a timing light set up so you could see the balancer as you were going down the highway, you'd see about 50 degrees advance (10 degrees initial, 20-25 degrees from the centrifugal advance, and 15 degrees from the vacuum advance) at steady-state cruise (it only takes about 40 horsepower to cruise at 50mph).

When you accelerate, the mixture is instantly enriched (by the accelerator pump, power valve, etc.), burns faster, doesn't need the additional spark advance, and when the throttle plates open, manifold vacuum drops, and the vacuum advance can returns to zero, retarding the spark timing back to what is provided by the initial static timing plus the centrifugal advance provided by the distributor at that engine rpm; the vacuum advance doesn't come back into play until you back off the gas and manifold vacuum increases again as you return to steady-state cruise, when the mixture again becomes lean.

The key difference is that centrifugal advance (in the distributor autocam via weights and springs) is purely rpm-sensitive; nothing changes it except changes in rpm. Vacuum advance, on the other hand, responds to engine load and rapidly-changing operating conditions, providing the correct degree of spark advance at any point in time based on engine load, to deal with both lean and rich mixture conditions. By today's terms, this was a relatively crude mechanical system, but it did a good job of optimizing engine efficiency, throttle response, fuel economy, and idle cooling, with absolutely ZERO effect on wide-open throttle performance, as vacuum advance is inoperative under wide-open throttle conditions. In modern cars with computerized engine controllers, all those sensors and the controller change both mixture and spark timing 50 to 100 times per second, and we don't even HAVE a distributor any more - it's all electronic.

Now, to the widely-misunderstood manifold-vs.-ported vacuum aberration. After 30-40 years of controlling vacuum advance with full manifold vacuum, along came emissions requirements, years before catalytic converter technology had been developed, and all manner of crude band-aid systems were developed to try and reduce hydrocarbons and oxides of nitrogen in the exhaust stream. One of these band-aids was "ported spark", which moved the vacuum pickup orifice in the carburetor venturi from below the throttle plate (where it was exposed to full manifold vacuum at idle) to above the throttle plate, where it saw no manifold vacuum at all at idle. This meant the vacuum advance was inoperative at idle (retarding spark timing from its optimum value), and these applications also had VERY low initial static timing (usually 4 degrees or less, and some actually were set at 2 degrees AFTER TDC). This was done in order to increase exhaust gas temperature (due to "lighting the fire late") to improve the effectiveness of the "afterburning" of hydrocarbons by the air injected into the exhaust manifolds by the A.I.R. system; as a result, these engines ran like crap, and an enormous amount of wasted heat energy was transferred through the exhaust port walls into the coolant, causing them to run hot at idle - cylinder pressure fell off, engine temperatures went up, combustion efficiency went down the drain, and fuel economy went down with it.

If you look at the centrifugal advance calibrations for these "ported spark, late-timed" engines, you'll see that instead of having 20 degrees of advance, they had up to 34 degrees of advance in the distributor, in order to get back to the 34-36 degrees "total timing" at high rpm wide-open throttle to get some of the performance back. The vacuum advance still worked at steady-state highway cruise (lean mixture = low emissions), but it was inoperative at idle, which caused all manner of problems - "ported vacuum" was strictly an early, pre-converter crude emissions strategy, and nothing more.

What about the Harry high-school non-vacuum advance polished billet "whizbang" distributors you see in the Summit and Jeg's catalogs? They're JUNK on a street-driven car, but some people keep buying them because they're "race car" parts, so they must be "good for my car" - they're NOT. "Race cars" run at wide-open throttle, rich mixture, full load, and high rpm all the time, so they don't need a system (vacuum advance) to deal with the full range of driving conditions encountered in street operation. Anyone driving a street-driven car without manifold-connected vacuum advance is sacrificing idle cooling, throttle response, engine efficiency, and fuel economy, probably because they don't understand what vacuum advance is, how it works, and what it's for - there are lots of long-time experienced "mechanics" who don't understand the principles and operation of vacuum advance either, so they're not alone.

Vacuum advance calibrations are different between stock engines and modified engines, especially if you have a lot of cam and have relatively low manifold vacuum at idle. Most stock vacuum advance cans aren’t fully-deployed until they see about 15” Hg. Manifold vacuum, so those cans don’t work very well on a modified engine; with less than 15” Hg. at a rough idle, the stock can will “dither” in and out in response to the rapidly-changing manifold vacuum, constantly varying the amount of vacuum advance, which creates an unstable idle. Modified engines with more cam that generate less than 15” Hg. of vacuum at idle need a vacuum advance can that’s fully-deployed at least 1”, preferably 2” of vacuum less than idle vacuum level so idle advance is solid and stable; the Echlin #VC-1810 advance can (about $10 at NAPA) provides the same amount of advance as the stock can (15 degrees), but is fully-deployed at only 8” of vacuum, so there is no variation in idle timing even with a stout cam.

For peak engine performance, driveability, idle cooling and efficiency in a street-driven car, you need vacuum advance, connected to full manifold vacuum. Absolutely. Positively. Don't ask Summit or Jeg's about it – they don’t understand it, they're on commission, and they want to sell "race car" parts.

I think you misunderstood my post. I was guessing those two things about YOU based on how much of this has already been covered in this thread and the structure of your sentences. If you'll read back over some of the previous posts in this same thread, you'll find quite a detailed description of timing, vacuum, etc that has been extensively discussed. We'll find out the real cause when the OP completes his investigation. I'm betting on the radiator.

it seems this thread has lost it's course and i guess the op will advise us as to the fix
somebody please lock this discussion, it has been beaten to death....jmo.....

N:cheers:o problem

The order has been placed for DeWitt's most capable radiator for this application (SP020).

A couple weeks from now and I hope to have good news.


http://cdn.shopify.com/s/files/1/016...rande.jpeg?666

Just saying!:thumbs:

You can use your shroud with that setup. Just like mine.

:cheers:

:thumbs: Good call.....but no gloating allowed :D

Dennis:cheers:

Also check theromstat location for fan they make one that goes right under hose connection on intake .

overheating
 

two things that are paramount are: make absolutely sure that you
have a spring in your lower radiator hose and also make sure that
your fan blades are at least halfway inside your shroud.

if either of these things are not done your motor will defininately
overheat? good luck

Frankie :cheers::cheers:

Good point !:iagree:

I think you are way overstating some minor contributing factors. By the way, what should I do with the new radiator hoses that don't have a springs in them?

I ran my '63 a whole summer a couple years ago with NO FAN at all on it. Get's very hot here. As long as I kept moving, no overheat problem. I could make at least three laps around the courthouse square and/or sit at three stop lights before the temp gauge started to rise above 180*. As soon as I got moving, no more drama.

Same way with slow timing. It has to be WAY OFF for it to be the cause of overheat. It could be a contributing factor if it's some slow but if it is, you have something basic wrong that you need to address.

Same exact piece I have in my 63 roadster 165 - 180 all day long in traffic and 180 - 190 @ 70 MPH with fan off. You will be pleased.

You know it could be why did they put a spring in there to start with
I rembemer riding in big block 67 corvettes around silver spring in maryland with no problem on maney hot days . They were stock and had alumimun raditors . But movenment of air and the shroud is very important and and if the thermostate not right ,or the gas line is boiling laying on the intake all this stuff could casue problems a small block with a Dewitts alumimum should never overheat .if vacume is right and timing correct .
If you havent put the radiator in yet it takes 5 minutes to add a lower hose.at 23.00 I :crazy2: bet you would not need the electric fan.

If you don't go back and edit out all the disconnected statements and sentences, nobody is going to read it anyway.

In a nutshell, I believe all that article(s) says is make sure your cooling system meets stock specification and you won't have problems. Imagine that!:D

Otherwise, what is your point?

The whole idea on this forum is to fix your midyears. Now if thats not the intent I will have to edit this so I can publish this to your satisfaction. Tell the guy that laying on his garage floor or stuck in traffic next time to do a spell check before he takes a spin.
Whats your point this is the second time on this post that someone
gave me a hard time trying to help someone. You know so much solve the guys problem Im through :cool:

Here's one of John's technical articles on Corvette cooling with all the pretty pictures to go along with the discussion:

http://www.camaros.org/pdf/corv_cooling2.pdf

-- Steve

I thought you were an a real engineer? What you posted was just incoherent babbling, indecipherable to most/many. In it's original form, precise and to the point.

Do you think if your fan clutch lost 5% of it's capability the engine would overheat?

Do you think if the radiator scaled up and lost 5% of it's capacity the engine would overheat?

Do you think if the ignition timing slipped 5% slow, the engine would overheat.

Do you think if the thermostat opened 5% less the engine would overheat?

The answer is probably "no"!

It takes a complete failure on one or more of those systems to make an engine overheat or a partial failure of a combination of several of them.

And yes, I've had engines that overheated for all of the above reasons but in every case, it was an almost complete failure of one of those systems.

Thanks I NEEDED THAT ! Let Mike see this is the same article in a modern verson .
This article I pasted was from 1993 that helps the regular guy fix his midyer corvette .With the pictures and the way the article is written is easy to understand .Thanks for the good article .:cheers::cheers:

OK Mike ,I like to get to the real problem and fix things I am an Engineering Teck dont take this the wrong way
looked at you post on vacume and overheating and know you dont
want to debate this but read this article on vacume that explains how
vacume does cause overheating ,if you dont want to comment that fine also .Richard

This was written by a former GM engineer as a response to a similar question on a Camaro board:


As many of you are aware, timing and vacuum advance is one of my favorite subjects, as I was involved in the development of some of those systems in my GM days and I understand it. Many people don't, as there has been very little written about it anywhere that makes sense, and as a result, a lot of folks are under the misunderstanding that vacuum advance somehow compromises performance. Nothing could be further from the truth. I finally sat down the other day and wrote up a primer on the subject, with the objective of helping more folks to understand vacuum advance and how it works together with initial timing and centrifugal advance to optimize all-around operation and performance. I have this as a Word document if anyone wants it sent to them - I've cut-and-pasted it here; it's long, but hopefully it's also informative.

TIMING AND VACUUM ADVANCE 101

The most important concept to understand is that lean mixtures, such as at idle and steady highway cruise, take longer to burn than rich mixtures; idle in particular, as idle mixture is affected by exhaust gas dilution. This requires that lean mixtures have "the fire lit" earlier in the compression cycle (spark timing advanced), allowing more burn time so that peak cylinder pressure is reached just after TDC for peak efficiency and reduced exhaust gas temperature (wasted combustion energy). Rich mixtures, on the other hand, burn faster than lean mixtures, so they need to have "the fire lit" later in the compression cycle (spark timing retarded slightly) so maximum cylinder pressure is still achieved at the same point after TDC as with the lean mixture, for maximum efficiency.

The centrifugal advance system in a distributor advances spark timing purely as a function of engine rpm (irrespective of engine load or operating conditions), with the amount of advance and the rate at which it comes in determined by the weights and springs on top of the autocam mechanism. The amount of advance added by the distributor, combined with initial static timing, is "total timing" (i.e., the 34-36 degrees at high rpm that most SBC's like). Vacuum advance has absolutely nothing to do with total timing or performance, as when the throttle is opened, manifold vacuum drops essentially to zero, and the vacuum advance drops out entirely; it has no part in the "total timing" equation.

At idle, the engine needs additional spark advance in order to fire that lean, diluted mixture earlier in order to develop maximum cylinder pressure at the proper point, so the vacuum advance can (connected to manifold vacuum, not "ported" vacuum - more on that aberration later) is activated by the high manifold vacuum, and adds about 15 degrees of spark advance, on top of the initial static timing setting (i.e., if your static timing is at 10 degrees, at idle it's actually around 25 degrees with the vacuum advance connected). The same thing occurs at steady-state highway cruise; the mixture is lean, takes longer to burn, the load on the engine is low, the manifold vacuum is high, so the vacuum advance is again deployed, and if you had a timing light set up so you could see the balancer as you were going down the highway, you'd see about 50 degrees advance (10 degrees initial, 20-25 degrees from the centrifugal advance, and 15 degrees from the vacuum advance) at steady-state cruise (it only takes about 40 horsepower to cruise at 50mph).

When you accelerate, the mixture is instantly enriched (by the accelerator pump, power valve, etc.), burns faster, doesn't need the additional spark advance, and when the throttle plates open, manifold vacuum drops, and the vacuum advance can returns to zero, retarding the spark timing back to what is provided by the initial static timing plus the centrifugal advance provided by the distributor at that engine rpm; the vacuum advance doesn't come back into play until you back off the gas and manifold vacuum increases again as you return to steady-state cruise, when the mixture again becomes lean.

The key difference is that centrifugal advance (in the distributor autocam via weights and springs) is purely rpm-sensitive; nothing changes it except changes in rpm. Vacuum advance, on the other hand, responds to engine load and rapidly-changing operating conditions, providing the correct degree of spark advance at any point in time based on engine load, to deal with both lean and rich mixture conditions. By today's terms, this was a relatively crude mechanical system, but it did a good job of optimizing engine efficiency, throttle response, fuel economy, and idle cooling, with absolutely ZERO effect on wide-open throttle performance, as vacuum advance is inoperative under wide-open throttle conditions. In modern cars with computerized engine controllers, all those sensors and the controller change both mixture and spark timing 50 to 100 times per second, and we don't even HAVE a distributor any more - it's all electronic.

Now, to the widely-misunderstood manifold-vs.-ported vacuum aberration. After 30-40 years of controlling vacuum advance with full manifold vacuum, along came emissions requirements, years before catalytic converter technology had been developed, and all manner of crude band-aid systems were developed to try and reduce hydrocarbons and oxides of nitrogen in the exhaust stream. One of these band-aids was "ported spark", which moved the vacuum pickup orifice in the carburetor venturi from below the throttle plate (where it was exposed to full manifold vacuum at idle) to above the throttle plate, where it saw no manifold vacuum at all at idle. This meant the vacuum advance was inoperative at idle (retarding spark timing from its optimum value), and these applications also had VERY low initial static timing (usually 4 degrees or less, and some actually were set at 2 degrees AFTER TDC). This was done in order to increase exhaust gas temperature (due to "lighting the fire late") to improve the effectiveness of the "afterburning" of hydrocarbons by the air injected into the exhaust manifolds by the A.I.R. system; as a result, these engines ran like crap, and an enormous amount of wasted heat energy was transferred through the exhaust port walls into the coolant, causing them to run hot at idle - cylinder pressure fell off, engine temperatures went up, combustion efficiency went down the drain, and fuel economy went down with it.

If you look at the centrifugal advance calibrations for these "ported spark, late-timed" engines, you'll see that instead of having 20 degrees of advance, they had up to 34 degrees of advance in the distributor, in order to get back to the 34-36 degrees "total timing" at high rpm wide-open throttle to get some of the performance back. The vacuum advance still worked at steady-state highway cruise (lean mixture = low emissions), but it was inoperative at idle, which caused all manner of problems - "ported vacuum" was strictly an early, pre-converter crude emissions strategy, and nothing more.

What about the Harry high-school non-vacuum advance polished billet "whizbang" distributors you see in the Summit and Jeg's catalogs? They're JUNK on a street-driven car, but some people keep buying them because they're "race car" parts, so they must be "good for my car" - they're NOT. "Race cars" run at wide-open throttle, rich mixture, full load, and high rpm all the time, so they don't need a system (vacuum advance) to deal with the full range of driving conditions encountered in street operation. Anyone driving a street-driven car without manifold-connected vacuum advance is sacrificing idle cooling, throttle response, engine efficiency, and fuel economy, probably because they don't understand what vacuum advance is, how it works, and what it's for - there are lots of long-time experienced "mechanics" who don't understand the principles and operation of vacuum advance either, so they're not alone.

Vacuum advance calibrations are different between stock engines and modified engines, especially if you have a lot of cam and have relatively low manifold vacuum at idle. Most stock vacuum advance cans aren’t fully-deployed until they see about 15” Hg. Manifold vacuum, so those cans don’t work very well on a modified engine; with less than 15” Hg. at a rough idle, the stock can will “dither” in and out in response to the rapidly-changing manifold vacuum, constantly varying the amount of vacuum advance, which creates an unstable idle. Modified engines with more cam that generate less than 15” Hg. of vacuum at idle need a vacuum advance can that’s fully-deployed at least 1”, preferably 2” of vacuum less than idle vacuum level so idle advance is solid and stable; the Echlin #VC-1810 advance can (about $10 at NAPA) provides the same amount of advance as the stock can (15 degrees), but is fully-deployed at only 8” of vacuum, so there is no variation in idle timing even with a stout cam.

For peak engine performance, driveability, idle cooling and efficiency in a street-driven car, you need vacuum advance, connected to full manifold vacuum. Absolutely. Positively. Don't ask Summit or Jeg's about it – they don’t understand it, they're on commission, and they want to sell "race car" parts.
:D

IBTL :lurk:

"I am an Engineering Teck"

Ten years ago you couldn't even spell "tech" and now you am one.

Some day i will get it right and strive to be that perfect person until then I am the teck i have no problem with that :thumbs:

From the article you quoted this is the bottom line and I agree with it:

"For peak engine performance, driveability, idle cooling and efficiency in a street-driven car, you need vacuum advance, connected to full manifold vacuum."


The key word here is "peak".

Lack of vacuum advance to the factory specification doesn't necessarily CAUSE overheating. It DOES increase exhaust gas temperature. Some of that increase goes out the tailpipe, some of it is radiated to underhood and some of it is radiated to the cooling system.

If your car is up to snuff in all areas except for lazy timing, you likely won't notice any increase in your temperature gauge. If you do, it will be very little. This is a fact that many people that haven't had any experience with engines ignore. Maybe lots of reading experience
though.

What is an engineering teck or tech? Just curious.

And I see you didn't comment on my questions about other contributing cooling/heating factors.

guys... please let's table this debate until he gets a new radiator installed and see what the results are.

if that doessn't fix it, let the stones and missles continue to fly... :rant:
Bill

:grouphug:

This thread was a train wreck by the end of the first page!

:D

Mike I agree with all those points...you are correct. I thought you would actually like this artice I found.
I have a 63 corvette matching numbers matching carb etc,NCRS its a powerglide. Two weeks ago after installing engine and carb I had an overheating problem. This younger mechanic called his buddy heard him talking he said why does this carbuator only have 1 vacuum input
at front of carb.
He said he will block it off I tried to show him the article on vacuum he told me I am not reading that crap off internet will put car on dyno,
but I can't help with your overheating problem. He helped me get the engine started for the first time.
I pulled the car away from him and took it to guy that works and specializes in old stock corvettes .
He set everything up, timed it and we had to send carb back to Chicago vets for another rebuild this time with Cam specks from the Machine shop. Now the car will idle all day long w/o overheating with te vacuum hooked up.
I worked for Congress and supplied heating and air conditioning to them from Captial Power Plant . I am a Master electrician by trade
and held position of Engineering Tech -Electrical and High Voltage .
I hate to tell anyone that the way Congress is doing theas days.

You said you had a fulieI like to see that Thanks Richard :lol:

Dangerous!But it's exciting

Don't know very much about corvette over heating history? I raced round track years ago and had a water pump go bad on a 355 cid motor. a friend of mine brought a new corvette pump to shop to get me back to the track. it ran hot first time out, filled it back up with water and went out again, same thing happened. Got back to shop took the pump off and removed the back plate to find the impeller was built reversed! After a lot of research, i found that there was at least 1 year the pump ran backwards??? Changed pump an had no more problems???? Never would have believed it but that's what it was?

I can't seem to find where I mentioned it, but I bought a new pump from Napa and the issue remained.

FYI:Before installing that new radiator, be sure and pull the block drain plugs (one on each side near the motor mounts) and flush very well. Heater core needs flushing also.:thumbs:

Tebok, I know you wont think it'll make a difference & many others here will argue. But try putting a 190 thermostat in it. Run your car & see what happens.
If it doesnt get your car to run under 210* I'll buy you a frosty beverage of your choice.

To explain my logic of my previous post.
You're currently running a 160 Tstat.
Now look at the picture of your rad temps
http://s11.postimg.org/3z6ygud03/Untitled.jpg
Is the temp entering the rad over 160*? =YES
Is the temp exiting the rad over 160*? =YES
Ok so when does your thermostat ever close, allowing the coolant in the radiator to cool enough to keep temps down?

I'm having some cooling problems myself so I've been following this thread closely. I don't know very much about the physics of all of this but if the thermostat closes (any temperature thermostat), wouldn't that make the engine even hotter since water in the block has no way to cool? Again, I'm not questioning what you're saying, I just don't understand the science behind the premise.

-- Steve

BTW, there's a terrific article about engine cooling written by John Hinckley in the current issue of "The Corvette Restorer". He explains the function of each of the components and how they work with each other to keep things cool. It's imply written and easy to understand. Great article!

-- Steve

If you read the first post in this thread, you'll see that I refer extensively to Mr. Hinckley's article. It's a good one.

Thanks for the suggestion, and it certainly would be an easy one to try out. With all due respect, I doubt it would change anything.


Like Mr. Hinckley says,
"Thermostats have absolutely nothing to do with maximum engine operating temperature. Period."

Today's update:

DeWitt's has shipped the new rad!
http://wwwapps.ups.com/img/glo_ups_brandmark.gif

In addition, I was able to get the Vette out for a nice run yesterday. For the first time in a long time the temp in Denver was under 80 deg. I was able to drive for over 25 min without going over 210 deg. This required blasting the heater, but still was a great time!

Keep us posted about your results with the new radiator. My car goes into the shop tomorrow to assess/address its cooling problems. I'm guessing I'll end up with either a new radiator or an electric fan for my Vintage Air system.

-- Steve

Good luck sir. You too, please share what you've learned.

Steve to put it simply If the thermostat is able to stay closed longer the coolant in the radiator will have time to dissapate heat. When the stat is closed no water is moving so the rad can do its job as a air/water heat exchanger.
Here's the basic train of events. Engine heats coolant to opening temp of T-stat. As 'stat . opens water begins to flow,circulating out of radiator and into the block. as cooler water flows up to the 'stat it will once again close,thus halting circulation. Enabling coolant that has just been heated and pushed from the engine to sit in the radiator and dissipate its heat.
If coolant is unable to stop(by the closed T-stat) and dissipate heat in the radiator you will get a compounding heating effect of the coolant.

Give it a try Tebok. All you have to gain is a tall cool one:cool:

Steve I just read that you installed a V.A. Unit. Unfortunately any AC puts a condensor in front of the radiator thus dumping more heat in front of the radiators cooling airstream. Your AC system will benefit from a elec. fan in front of the condensor as it will help condense the Freon charge(also lower your AC's Hi side pressure). With the added heat dumped in front of the radiator you may have to go to a higher efficency radiator to help cool the engine.

Nope. Once it opens initially, the thermostat never closes until after the engine is shut off and cools down. It responds to the coolant temperature in the front intake manifold crossover passage and cycles, to modulate the rate of continuous coolant flow into the radiator and from the radiator into the water pump. Under no circumstances does it stop the flow of coolant. :thumbs:

IMHO this is very important. To take this one step further, prestone makes an engine flush that you pour into the radiator, then drive it for a while and drain it out. This will help loosen up the rust and scale buildup. Then reverse flush the block. This way the water can get behind the rust and push it out. I would hook up a hose to each drain port, (1/4" mip thread), and let it run for 5 minutes, then the upper radiator hose, then the lower hose. This is a messy job but is easily done with the engine in the car. Make sure the heater switch is in the hot position. Drain the block and refill with distilled water 50/50mix.
I believe the De Wits warranty becomes void if you use tap water.
I just did this to my A/C equipped 327 two months ago just prior to installing my new three row De Witts.

(both Ace Hardware) female hose swivel x 1/4" mip thread will screw into the block drain ports.
http://www.mistcooling.com/media/cat...ipe_swivel.jpg

These are placed in the radiator hose and will expand into a water tight seal when the water is turned on. (You can also use it clear a sink stoppage)
http://www.plumbersurplus.com/images...777-246235.jpg

Calling John Z
 

While we wait for the OP's radiator to come in I wanted to ask John Z a question related to this subject.

John

In your article on cooling you talked about the fan specifics such as half in half out of the shroud as well as the suggested distance from tip of fan to shroud being only one half inch.

Question 1

How can this half inch distance be? The 63 NCRS manual says the original fan diameter was 17 1/8". My fan is exactly 17" but I clearly have much more than your recommended clearance. Mine is about 1 1/8" to 1 1/4".

My fan matches the description in the manual but does not have a number on it.

I ask this because I'm having some temp creep at idle and not moving. I think this is a weak link in my system.

Also, I purchased a new fan clutch and did the spring trick to the front of it and that seems to make the fan engage better at the lower temps you describe that original units did.

Question 2. If the engine is hot and you shut it off and then run to the fan, should it not be engaged and not turn easily?? Meaning it is engaged because it is hot. Even my new one still turns hot. What gives? I must not understand how the clutch works.

Thanks in advance for responding. :thumbs:

Flushing the block is a great idea, you will have the system open so this is the perfect time to do the job correctly. My buddy installed a rebuilt 454 in his car, it ran hot, if you worked it at all it would overheat. We checked every single thing. No Luck. Finally flushed the block, found out this block had spent time in a Jet Boat and the block was half full of river bottom sand. A good flush fixed the overheating for him so it does happen, just not common.

FWIW, there is at least one poster on this forum that has his block mostly filled solid with whatever it is they use to stiffen cylinder walls. He has talked about higher oil temperatures but not higher cooling temperatures.

Just FWIW.

You should do a search on Westlatorn/fan clutch and read the excellent post he made here about a year ago about how fan clutches work.

Your symptoms and your clutch sounds normal to me.

Matter of fact, it should be a sticky here IMO.

Mike, Thanks for the kind bump.

I wonder if the Rock Block used to firm up oversize cylinders transfers heat better than Sand in a block?
They are both dense but Sand is still loose and not connected, might work like insulation?

My reason for flushing the block was to get any scale out that could clog that expensive new radiator.:thumbs: