1/2" to 3/4" was the original design clearance; the nature of the assembly process for the 4-piece welded shroud can introduce additional variation. I doubt if what you describe is a sole cause of your issue. :thumbs:

Read thru this thread and it seems you should start from the basics, since you really don't know what you have.
Prudent to clean the system first.
DO NOT do it after installing a new radiator.
Here is an appropriate cleaner, not the flush.

http://prestone.com/sites/default/p/...or_cleaner.png

Follow the directions, important to drive it hot long enough.
Prior to starting, with the existing coolant drained remove the block plugs, it will give you a good indication of the condition of the coolant passages.
Further, removal and rinsing using the plugs after flushing is essential for a proper cleaning.

Here are a couple pics, one of the block drains plugged (rather common) and another of just a small portion of the crap that was removed.
BTW, the engine was NOT overheating in S Florida and the coolant looked clean and green.

Once you start with a clean system and new rad you can more intelligently diagnose any cooling problems.

http://i74.photobucket.com/albums/i2...Pluggedjpg.jpg

http://i74.photobucket.com/albums/i2...oling/Crud.jpg

http://i74.photobucket.com/albums/i2...ng/Crudjpg.jpg

pressure test the cooling system at temp to see if you have a cracked head or block

Wow all through this thread thought we were talking about a clean block ,new or magnafluxed , hes right start at square 1 nothing else matters till that is clear.

Wow! I bet you're on to something!

:D:lurk:

Yup.

The fallacy of the water-is-moving-too-fast-through-the-radiator-to-cool argument, is the other side of the equation is ignored. That the water is also moving through the block too fast to pick up any heat. If you slow water on the cooling side to make it cooler, you also slow water on the heating side, so it gets hotter. You are going to get some delta T across the radiator, depending on the flow velocity, higher vels means lower delta T, but same on the block side, higher flows mean less heat is picked up, also a lower delta T

It is a closed system, if fluid flow velocity increases on one side, thus they have to increase on the other side.

Doug

OP Update


After DeWitt's finally got me all the parts (wiring harness was not shipped at first), I have removed the radiator.

Tonight I plan on finishing the install, but I cant find the port for the thermostat switch.

Where did you guys with electric fans install your temperature switch?

Also, are there any mods to the shroud that need to be done?

I put the thermo sensor in the T stat housing. I bought a housing with a threaded port.

Note that if this is a simple on/off switch,a nd not a thermistor for PWM controller, you may have to change your switch in the future so you fan either doesn't run all the time, or doesn't come on too late.

For an on/off, 195 would probably be my starting point.

In my 327/250 HP power '37 Ford pickup, there is no engine driven fan at all, and the electric fan almost never comes on, only if I am stopped, with the motor running for more than a few minutes, will it come on. A few minutes after I start moving again, the fan goes off.

Doug

I used the coolant by-pass port.

If I am not mis-taken JohnZ told me they actually run cooler when deleting the water pump by-pass anyhow.:thumbs:

Now that's a nice clean option. Thanks!

When you get a little time, see if you can explain that one to me.

When you get a little time, see if you can explain that one to me.

I feel for you - soon after I bought my 65 (L76 like yours) it became quite apparent why the seller only kept it a year - he had been chasing an chronic overheat problem, and then I was chasing the same problem.

He had installed electric fans, a cooler t-stat, a higher pressure rad cap, even a new rad . . . of course, none of that addressed the problem. In the first few weeks of my ownership once I discovered the problem, I tried a rigid fan set up (to rule out the fan clutch), and made sure the timing was set to specs. Still, every outing ended in overheating (per the gauge, and often with coolant puking.)

Eventually, I drained the cooling system and opened up the block drains, flushed the system and drained it completely again; put the proper 180 t-stat in there (if nothing else to rule out a non-functioning t-stat); replaced the nearly-new copper / brass rad that the p.o. had installed with a new Dewitts rad in there (exact repro of the Harrison stacked plate aluminum rad the SB C2 came with), tried a few Wells sending units until I got one that was telling the truth to my temp gauge (using an IR gun), ditched the electric fans and installed a new and proper fan clutch with correct fan; installed a new [rebuilt correct] water pump; and of course a new lower rad hose.

I am sure there are a bunch of postings from me on this forum in 2003 which outline this saga.

Problem solved, and I no longer glance nervously at the temp gauge every minute or so. I think the biggest impact was the Dewitt repro Harrison stacked plate aluminum rad, which has ~ 25% greater cooling capacity than the same sized copper / brass unit that I had in there. Plus, Tom Dewitt himself helped me sort out some issues I had during the install - a super guy.

If you have tried everything (timing is correct, water pump is operating as designed, cooling system has been flushed thoroughly to ensure no partial blockage inside the coolant passages in the block or manifold; fan clutch is new or has been ruled out, fan itself is the proper one; lower rad hose is not collapsing; proper amount of coolant is present), and you have confirmed with an IR gun that your car is truly still overheating, then I definitely agree you need to revisit that radiator you have in there now - whether it's not capable or it's not functioning as it should. I see you have gone ahead and gotten Tom Dewitt involved - good call.

:iagree::iagree::This is it you hit the nail on the head I kept telling people that you dont need the flex fans and all that extra ******** on there. I had same problem and went back to the way it was design to work Good post

If you are running a/c in hot climate that electric fan sure makes a difference.

Mine is set up to factory standards. And works as intended.

But no way it will sit in traffic at 95 degrees with a/c on without it climbing over 200+ without the SPAL fan. I don't get in traffic much. But I do use the fan fo a cool down after stopping.:thumbs:

Thanks for the input. It's good to know that a similar situation was resolved with a DeWitt's radiator.

I wish I could have got some input from Tom DeWitt the way you and others have been so lucky to recieve. My experiance with their company is average at best. Shipping updates and tracking numbers would have been nice. The lady who always answers the phone is nice, but not very knowledgable with technical questions. I also had the wiring harness miss the first shipment and had to wait three days to get it. At least the shipped it out first class. Let's hope their product is as good as everyone says it is.

I was able to get him when I had a technical question. You could always ask to speak with him. He also responds here on the forum.:thumbs:

Good to know. Hopefully all I have to say is "Thank you" after installing his radiator.

My experience - the correct fan shroud, correctly installed (and perhaps all gaps insulated as you get with an A/C car) in conjunction with the correct fan, positioned correctly on a fan clutch (which locks up per spec) keeps a C2 Corvette from running too hot on a hot (90 degree and +) day. Even when I had an A/C compressor on my car (VA, since removed).

I'd politely suggest that these cars, when new, were capable of being run on a hot day with the A/C on without overheating. Hence my decision to "return everything to oem condition" to put the overheating situation behind me, which worked for me.

Nope. You didn't hear that from me - must have been someone else. :willy:

Sorry about that. I did add a memory disclaimer.:D

Then by-passing the by-pass is not a good idea?

Do you (or anyone reading this) have a part number for a water neck that's threaded for a sensor?

Thanks.:thumbs:

Jeg's has them - there was a thread on just that issue (with pics of the Jeg's housing) 2 or 3 days ago. :thumbs:

Big difference between Conn. climate and Houston. How it's being driven with a/c on also makes a big difference. I tend to let it rip when I drive. Builds heat fast. No problem with parade or even brisk driving.

The ability to cool down a triple black C2 is worth the fan alone.

Under hood temps plummet when you need them to. Makes for an easy start in the hottest weather.Was 101 here today.

As I said before. Mine is up to spec shroud and all. Mine is in OEM condition also. Other than VA and SPAL. Anyone who knows my build knows I have taken full advantage of every "correct" suggestion here on the forum. I will be changing the sensor position though.

Go to thread
restortion on my 64 coup here is a picture to the left is a part everone is using to control fans go to thread he explans it very well

Water Outlet
 

You can also get one at any local auto parts store. GM first started to use them in 74 or 75 when they started using a vacuum operated EFE valve (fancy name for the heat riser). Bring the switch with you, as the threaded holes changed sizes over the years.

Can you provide the link to said thread?

I remember having this issue with my 67 GTO in 1970. I had thought removing the thermostat would allow for cooler temps. It did not. I was told by an old mechanic that slowing the flow actually enables the fluid to be more effectively be cooled via the air transfer through the radiator cooling fins. He was correct. Once the factory spec thermostat was installed, no more issue.

You can get one from Four Seasons from your local parts store.
The retail under $15.00.
Joe

http://www.4s.com/Online%20Catalogs-...g/Content.aspx

Thanks. I'll send a message his way.

I just got back from visiting my car which is at my mechanics. He told me the same thing. If you remove the thermostat, the coolant moves too fast through the radiator to have enough time to cool.

-- Steve

Not looking for a pissing match as to who lives in a hotter climate (you can claim that "prize", the difference is ~8 degrees av high temp for the summer months - I looked it up :D ) or who drives their car with more "spirit" (we can call that a draw :auto: - but I'd suggest that parade duty on a hot day would be the most demanding test of a C2's cooling system, not that I have ever been in a parade - but stop and go traffic, yes.) I do stand by my assertion that plenty of these 63 - 67 SB Corvettes were sold, even in SoCal, NM, AZ, TX, FL, etc. with a/c, and they were capable of being run in the summertime without needing to be parked in the shade until October due to overheating problems. Without an electric fan replacing the oem unit.

And I am certainly not questioning the quality of your build :hide:

Yes and they had 7 blade fans and were still marginal in Texas heat.

Was out with mine today. After an hour of driving in noon time heat plenty of starts and stops. I get a steady IR and gauge reading of 210 with a/c and no fan. The fender was 140. And that's normal when temps are 95.
But as I said before, I use my fan mainly to cool down the car at short stops and after hot drives. Makes for very easy re-starts. Black cars have a 40% increase in body temps over light colors.

There is a valid reason for an electric fan on many levels. Matter of preference I guess.

Now if you want get in a pissing match and make me repeat myself for a third time? Go for it!:cheers:

Rat dog that is beatiful Vet love white and blue top,
I had a 63 split window which was white and a 2007 convertable with a blue top must be the white / blue That sets off the car .

When I sold my split window in 2007 people in the market told me white was unpopular .Still to this day I dont believe that .I am painting my split now to Sebring Silver only because its a sebring silver vet .Who cares take the thermostate out ,nice vet :smash:

Rat dog that is beatiful Vet love white and blue top,
I had a 63 split window which was white and a 2007 convertable with a blue top must be the white / blue That sets off the car .

When I sold my split window in 2007 people in the market told me white was unpopular , and investnment wise it was not good Still to this day I dont believe that .I am painting my split now to Sebring Silver only because its a Sebring Silver vet . ,nice vet Still wanted to show the blue tops I have had and are my favoites:smash:

Thanks for the nice words. I like blue tops, too. I like white cars and the color of the top on this one is what drew me to it. They only made 611 cars with blue tops in '67.

-- Steve

My experiences with oem cooling have been that these systems work well when new. However, I prefer the electric fan over the oem setup...oem is what it is, and I have had many older cars from the 60s era and the oem systems work provided all the sub systems are in top condition...however, not much margin for error and adding a/c, black paint and 95 degree temps, elevation, etc, further reduces that margin. Air flow is fair through the grill on C2s and it gets worse with the C3 design...had one of those as well and it ran hot all the time even after refurbing the oem system.

As a reference, in my 67 I run a 450hp 383 with a Dewitts rad/electric fan at 7K+ altitude and an electric fuel pump. With the lower boiling temps, overheating and vapor lock are all too common...oem fuel pump and oem cooling didn't make the grade. By the way, the car was doing the same when I bought it and it was at sea level down in San Antonio...oh yeah, it was 95 degrees + when I test drove it...no a/c and its blue...

Anyway, I prefer the engine compartment without a shroud and a fan blade...makes it easier to clean and work if necessary.

To each his own...do what works for your car and that is really all that matters...

Frank

Bump

Any update on this overheating problem?

Yeah, John, Any update on the over heatin???willy:Now get off the Forum and get back to work. We need those electrical supports designed NOW!!!:rofl:

Nice one buddy. Back in Jersey and supporting your guys the best we can, 'cause that's what Structural guys are here for. :rofl:

OP Update: Good news
 

The good news:
The DeWitt's radiator is installed and is working like a dream. It can idol and cruise around the city all day. The initial test was in the garage where at idol it raised up to 195, the fans kicked on, and it dropped back down to 175. I let it go through two cycles of raising up and falling down to my delight.

OP Update: Bad news
 

The bad news:
Cruising the highway speeds shoots the temps up. It never breeched 240 (probably cause it was a cool 75 deg out that day), but came damn close.

I'm thinking that the radiator just cant keep up with the high rpms.

Note:
Highway speeds = A sustained speed at or around 70 mph with an rpm of about 3750

That's good news, tebok. My '67 is in the shop awaiting the arrival of a Dewitts with electric fan. Hope my results are as good as yours. My car did pretty well with cooling unless I ran my A/C (Vintage Air) in stop and go traffic with 90+ outside temps.

[I just read your "bad news" message :( ]

-- Steve

Something else is happening to you. I have new DeWitts and at cruise 70+ at higher RPMS and it cools right down to stat temp. I'm having a bit of temp creep at idle so am checking fan clutch.

run a block check with liquid that changes color to see if you have a combustion leak.....jmo.....:cheers:
have you changed the water pump?.....sorry you are going through this

Thanks for your input, but please read the thread through before posting.

Both these checks have been done.

I've been following along. Just a FYI. I have a zz383 with a Dewitt radiator and 3:55 rear end. 180* thermostat. Stock fan and fan clutch. Mine runs 180* ALWAYS. Stop light to stop light, 90*+ air temp, 75mph for 200 miles on the highway etc. I know this doesn't solve your issue but you should expect better results.

Dennis:cheers:

sorry, the thread is too long and it rambles, i will just stay out of it to avoid further confusion but do wish you luck and will assume all the possibilities have been covered as to blockage, combustion leaks, backwards fan, water pump and rotation collapsed hoses and the like....:cheers:
i will tune in at times to see if you solve it....:rock:

If it's the exact reproduction of the original Harrison stacked plate aluminum radiator you purchased from Dewitt and installed, you have the most efficient (from a heat exchange standpoint) radiator that will fit in that OEM space. And is the same radiator that these cars were sold with when new, so it is definitely able to keep up with higher RPMs. (Also the same radiator I have in my 65 L76 (365 hp), which I can personally attest to being able to run at highway speeds with a "steady 180" showing on the temp. gauge.)

It is quite likely you had multiple causes feeding into your initial overheating condition. I did too. For me, it was a combination of the wrong radiator, poorly functioning aftermarket carb, clogged cooling system, and airflow issues (including airflow through the entire radiator impeded by a previously-installed dual fan kit, which was replaced with a proper fan and oem fan shroud) - all were contributing to my situtation. In my case, the first thing I did when tackling this issue was replace the radiator with the exact replica unit from Dewitt, which helped, but did not cure, my overheating situation. So I feel for you - been there. You have certainly addressed the radiator piece, and now can focus on other contributors.

With all that said, you must be extremely frustrated. I certainly was, when I was in your shoes.

Have you checked if the fans are blowing or sucking air? If your fans are turning in the wrong direction they will help cooling the radiator in your garage, but when they are on at highway speed they are blocking the airstream through radiator.

I agree Dennis, that I should expect better results.

I'm coming to the conclusion that this isn't a simple cooling issue and that it's internal. The car runs well enough now that I can enjoy it and that's most likely where it will stay until I have the time and money to deal with the motor internals.

Good point!

Yes, I have confirmed that the fan is pulling as designed.

Well, the equal of that DeWitts radiator for my '61 car keep my 427 SB cool, though temps do creep up under full throttle passes down the 1/4 mile.

You have verified that there is no head gasket leak, you have a new rad and water pump. I would try one last little thing, even though your Tstat is new, it could be bad. I had a new Tstat fail, causing my car to overheat at highway speeds.

Take it out, put it in a pot of boiling water and make sure it is fully open.

Perhaps that .060" overbore, is simply too much, on your motor. Are you sure it is only .060" over, and someone didn't get creative trying to get more cubes out of it? Too thin of a cyl wall will give you high speed overheating.

Doug

I'm afraid you most likely are correct. The info I posted here is all that I have on the rebuild. I will certainly keep the numbers matching motor with the car, but maybe I'll swap it with another down the road some day when I have more cash. Time will tell

If it really is matching numbers, as the motor that came with the car, and not an e-bay restamp conjuration, you can always have the block sleeved. Just make sure they don't deck the numbers off.

If you just want to drive it, find a 327 or 350 and drop it in while you contemplate what to do with the original block.

Doug

At the first of this thread, it was suggested you double check your new thermostat. I don't recall you ever confirming you did. But maybe you did.

I could agree that thin cylinder walls will bleed more heat into the cooling system but doubt it would cause your remaining problem.

Re: the t-stat and the question of whether it's not opening, suggest using Mr. Gasket #4364 (the former Robert Shaw "fails open" t-stat in a 180 degree version). End of such worries.

Also wonder about the lower radiator hose possibly collapsing at high water pump speed. If replaced already maybe got a soft one, worth a try (although I loath replacing my lower rad hose, a real PITA). If trying that, use something like Paragon pn 1733 (correct hose, looks el correcto, and includes the spring inside to keep it from collapsing.)

Well I will just add my .02 here just because, I have been following this thread from day one and I'm up to date on everything you have done or tried.

So after all that if it was me this motor would now be setting on my engine stand. First thing I would do is remove the freeze plugs and have a look see inside the block for any blockage or heavy scale buildup. Next on my list would be a complete teardown and rebuild to stock specs. A 327/365hp motor is not something special and should run 180 degrees all day long. I had a 66 with a plain Jane 350 hooked up to a 30 year old stock radiator and this car never ran over 180 period.

Now the above might sound extreme but I’m a extreme kind of guy when something like this gets under my skin. I’m in the baby steps of dialing in my 427 on a run stand and I too am having temp problems right out of the gate so I feel your pain. But that is another thread for another day.

Hang tough, you will win this.

Dennis

If I recall where you have been already, Timing is good, Radiator is perfect now, water pump is replaced, Thermostat has been checked/replaced, no air in the system.
Engine passed the sniff test so no combustion in radiator.
You are running out of things that could cause this.
Now the remaining problem is high temp at freeway speeds only?
Thousands of 327's ran at .060 over with no heating issues, even in work trucks so I don't lean toward that.
Was the block flushed? I know there was lots of talk about it, did it flush and what came out?
Exhaust excessive back pressure can cause heat issues. Hard to test but worth a check.
Normally if you have this kind of back pressure issue you would also notice the engine power falling off.
With 4.11's spinning 3,750 you might not notice a 10-15% drop in power.
Did you pull the plate off the back of the water pump to inspect the impeller.
The low price units are not positive displacement and it may cavitate at the high RPM's.

Thanks Dennis. I agree with what you have to say and am leaning that way. I dont have the resources at this time to pull the motor, but it should make a nice winter project. You're right, it's gotten completly under my skin, but in the mean time I'm looking on the bright side. Something isn't right, but it's not causing any damage now and can be enjoyed at a non optimum level. For not, I'll take that.

I did flush the block recently and nothing crazy came out. Some fine particles, but nothing significant.

The exhaust has fresh free flowing flowmasters on it, so I doubt back pressure is an issue.

I have inspected both pumps that were in use and they are funstioning properly.

That is exactly the thermostat that i had that failed after less than 500 miles, and it never did work right, the car always ran too hot, and it finally stopped opening at all.. If the wax leaks out of the wax motor, it can't fail open, it fails closed. The fail open feature seems to nothing more than a lock mechanism that catches the valve in the maximum open position if it ever gets there.

NAPA replacement cured the problem.


.060" over shouldn't cause overheating, but maybe it was bored .125" over? .090'? Can't know until a head is pulled. Crap in the block would cause oil temps to rise, it wouldn't make the cooling system run too hot.

You are really OK at anything less than 235*F. Though carb perc would be really obnoxious after shut down.

http://www.flowkoolerwaterpumps.com/cooling_faq.html

This gives a decent question/answer on water pump issues

I feel your pain......
 

I went thru the same process[new DeWitt's, new pump, thermostat, fan clutch, check timing, etc] as you a few years ago. The new radiator was the last item for me, and like you, it wasn't the answer either. On my way to the Golden Gate bridge to jump off, I remembered one item that was easy to back track and check again. I removed my NEW Robt Shaw 180 deg. "never stick closed" thermo and put it in a pot of water on the stove. I turned on the heat and watched the water heat to a boil, but the thermo never opened! I exchanged it at my FLAPS for a new one and brought it home. I put it to the "stove test" before I installed it and it opened before my eyes. I then installed it and problem solved. I hope you get as "lucky" as I did, you deserve it-lib

Glad to hear of the improvement. I wouldn't pull the motor yet. You can remove both of the rear freeze plugs from under the car. Done it. Large screw driver and hammer. Can't remember if you power flushed it...suggest pulling the plugs then flushing again. After that, pull one head while its still in the car and check gaskets and passages. After that, The intake manifold. After that, pull it. Don't recall if you said which heads you have? Aluminum or original iron?

I have read through most of this thread and if temp climb going down the road.....it is insuffcient water flow.

I run a Weiand aluminum pump with a Mr. gasket stat...but as stated...these ARE NOT failsafe open....one trick I have been doing for years is I drill two holes along the "cup" of the stat at 6 and 12 o'clock.....this ensures flow no matter what and is not detrimental to the stats function.

I also run a New 6 blade original fan and clutch.....in South Texas...on a 100 degree day it might see 195 if it sits idling for 20 minutes or better in traffic.

Let me ask a stupid question: What is the diameter of your WP pulley?

Jebby

I :cheers: rembemer doing this in in 1964 on my 57 chevy

I was also having over heating problems. It came down to my solid lifter adjustment was to tight. Backed it off and it solved the problem.
Might be of interest to someone . Regards

:lurk::D

My contribution to overheating problems: My 1966 327 developed a sudden overheating problem. It could sit in the driveway idling and not overheat. Take a short trip around the neighborhood and it would overheat. The culprit was the vacuum advance controller. As rpm increased above idle speed, the lack of vacuum advance created a timing problem resulting in overheating. The vacuum advance is ACDelco part number 19110657 and is easy to replace. Available from numerous vendors but I bought from auto_parts_for_you_florida on ebay for $26.24.

Sorry to hear of your problems. I just spent all morning reading through the entire thread.
When I bought my 65 coupe last year, it overheated only when running the AC on a hot day. When the AC was off, no overheating. It had the overheating problems at idle and at highway speeds. I never let it get too close to being pegged, but it did get awfully close sometimes. For me, the immediate solution was to simply turn off the AC and the temperature went back to 180 in a few minutes. However, in Florida, this just is not an option in the coupe!
Just like you, I did not want to try the expensive option (new DeWitts radiator) first. Everyone told me this would fix everything, but I wanted to try the easy, cheap things first. I put in a 10 inch pusher fan first. It made no difference. I replaced the fan clutch with a spacer. It made no difference. I then tried a 12 inch puller fan (it would not fit as a pusher). It made no difference. I then tried a 14 inch puller fan. It made no difference. I then bought a 16 inch fan from a local auto parts place. When I got it home, I saw an "expensive" 16 inch fan on sale on eBay (an overstock). It had several hundred cfm's more than the fan I bought locally. I was about to put it on the radiator when, on a whim, I decided to test the actual cfm's of both fans. The expensive one turned out to be putting much less CFMs than the rating of the cheap fan and the cheap fan was putting out much more cfm's that the expensive one was rated. So I sent the expensive one back (they actually took the return without any hassle!) and put on the cheap 16 inch fan. Now, the cooling system never goes above the three quarter mark (I think that is the 240 temperature). That is the OK temperature for these AC coupes. Back when they were new, they were running that "hot". The TSB had the dealer install a new gauge to that put the 240 temp at the middle of the temp gauge. Nothing else was changed. People were happy as long at the needle pointed straight up and not towards the right.
Anyway, I solved my problem without a lot of expense. it sounds like your problem is still there. Keep us posted!

210 is straight up on the later gauges, not 240. If your car is running 240 with the A/C on, that is not good.

I had the same issues as you describe. Our summer heat here in Florida is brutal. I have a new Vintage Air system When the A/C was off, the car's temp ran at 210 (gauge accuracy verified with 2 IR guns). But when I turned on the A/C, the temp headed over to the 3/4 mark before too long, especially in traffic, so I'd have to shut down the A/C.

I replaced my radiator with the Dewitts model with the built-in SPAL fan. The SPAL fan cuts on at 210 and that's as high as it goes until I park and shut the engine off at which point it climbs to the 3/4 mark.

It seems like many of these older cars with A/C (either factory or add-on units) have trouble keeping their cool in the hot southern climates without a little extra help. For me, the solution was a Dewitts.

-- Steve

I couldn't remember the three quarter and end numbers on the gauge but I remember the gauge positions and that straight up is 180 degrees. Without the fan, the needle went past the three quarter mark, so I would turn off the AC to prevent "pegging" the needle. Fortunately, I have never had a boil over because I watched the needle and turned off the AC prior to allowing it to get way past the three quarter mark. Now, with the 16 inch fan, the needle never makes it to the three quarter mark. It is a hair prior to the three quarter mark, but rock solid at that position. I drove across Florida the other day, on the way back (more than 50 miles on the interstate highway), the radio said the outside temp was 94 degrees. Previously, that would have easily pushed the temp gauge needle past the three quarter mark.

My small block had the same problem a lot of people overlook this .
This is usually with original 63 to 67 small blocks :iagree:

Thanks for the suggestion. I've replaced the vacuum advance before, but not with this exact part number. For less than $20 on Amazon Prime, I figure why not!?!

Tebok,

You've resurrected this thread after almost two years. Are you still having the overheating issues? If not, what finally solved your problem?

The radiator made it manageable around town so I've been able to enjoy the car.

Issues have continued on long highway drives.

I read through that whole, long thread while ago.

At one point, you said your total timing (minus vacuum advance) was 32 degrees. Did you ever dial any more than that into the engine? It needs it. You said the initial was 14 which is good for idle. 32* not so good on the highway.


Another point. Did you ever confirm the thermostat was opening all the way? I never saw any reference to that.

Both of the above could give you heating problems at speed.

Thanks for putting in the time MikeM.

I'll have to go back and check the timing to give you a quality answer. I'd hate to take a guess from my cubicle. I will receive that new vacuum advance in a couple days and will come back with a full report on timing and results when I do.

I did confirm the t-stat was opening all the way and allowing good flow.

Where did you were all waiting still.

sounds to me like late timing, (leak in vacuum advance diaphram) allowing timing to retard in cruise. Cooling system cannot overcome excess cylinder temperatures.

:toetap:

Thanks for the input.

I had all the timing and hardware checked and tuned by a local pro/guru. Same result.

Next step is to remove the heads and check for clogs.

Update:
To all those who wonder how this old thread keeps coming up, my apologies. I am the father of three boys under the age of two and have been spending all my time and money on them. As soon as that frees up, I'll be throwing all of my resources at solving this mystery.

Its been setting for two years since then

Absolutely not. I just have to limit my drives to a 15 mile radius.

I do the same since my new engine rebuild over 3000 miles so far

i have been following this thread for a while now. and i must say i have the same problem with a 68 302 Z/28 .030 stock rebuild. so i am at a loss here also. i am hoping someone "pulls a rabbit out of there hat" here! and we figure this out..its cold here in mich but i am going to be looking at my timing first when the weather breaks. i do not want to high jack this thread. so i will be sitting back and reading..thanks guys keep up the good work..! troy:thumbs:

This thread is so old I just re read it and found I had posted a few times in this thread and forgot! Must be getting old.
A new thought for you. Flow can be blocked in many ways but two I have witnessed are excessive use of radiator stop leak and dummies knocking old freeze plugs into the block when they replace them and not removing them.

Wow, triplets, your going to need a second job! Hope you get it fixed.
Mark

Steam holes in newer blocks/heads and not using the proper head gaskets.

My dad told me that when the 50's and 60's cars were new they overheated. I remember a new 1960 Buick wagon he had overheating going up to Big Bear. He made a tight radiator shroud for it and solved the problem.

I gave up on mine and installed a Spal 16" puller fan inside the stock shroud on my '62 along with a 90 amp PowerMaster old school looking alternator. I put the stock fan clutch and fan back on. You don't even know it's there when the hood is up unless I lean down and point it out. Piece of mind even in 110 degree weather. I ran my car through the opening day parade at the L.A. County Fair on a hot day last year. Temp gauge never went over 180*. The C2 in front of me pulled out of line boiling over.

Installation:


https://cimg5.ibsrv.net/gimg/www.cor...e321986b87.jpg


Completed project.


https://cimg2.ibsrv.net/gimg/www.cor...f819e08853.jpg


Before:


https://cimg8.ibsrv.net/gimg/www.cor...44b7d0b6eb.jpg


After:


https://cimg9.ibsrv.net/gimg/www.cor...db9f422bc0.jpg


Parade:

Almost four years later, I am hesitant but ecstatic to say the overheating problem looks to be resolved.

The straw that broke the camels back was adding a rigid race fan in addition to the electric fan.

A range that was once limited to 15 miles turned into a drive well over 40 miles with sustained highway cruises at 70 mph and 3700 rpms. This was unheard of before, especially on a 70 degree day.

Much thanks to all of you for helping out with such great suggestions, banter, and support. Also thanks to Randy G. for putting the idea of running both fans back in my mind, williamarthurascs for bringing the thread (and my actions) back to life, and Bob Stone for the help with the tune.


https://cimg8.ibsrv.net/gimg/www.cor...ec662909fc.jpg

I must admit that was fast progress. Yesterday at 10:52 it remained a mystery limiting you to 15 mile drives and by 11:55 it was resolved and you're taking 40 mile drives. Is the date stamping of these posts screwed up?

There is a 17 +/- hour gap between my post and him stating the problem was solved. Even with no tools that's plenty of time to stick a fan back on.

Wow. My '62 with 3:36 rear end gear, 700R4 4 speed automatic overdrive and lock up converter, at 65 miles per hour the RPM's are about 1,990. My 430 HP 383 does pretty well on gas mileage at that rate.



https://cimg0.ibsrv.net/gimg/www.cor...61412b8280.jpg

:leaving: Hopefully, after many years and 297 posts, this thread will now go to that great storage device in the sky, for good...

I couldn't agree more.

Your mouse has many options. Including avoiding threads with 298 posts over many years. You should try it sometime.

I agree. Are you just trying to increase you post count? If you don't like thread for what ever reason don't click on it and certainly don't post a negative comment on it. I am sure this thread helped many members here as through the course of it, it covered ever conceivable fix for overheating.

:thumbs: