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?