newest event overheating AND...

[Francis F.]

The on going saga trying to get this old girl out of the safe haven of the garage.
on our trip around town today,engine temp continued to rise (215*) dash gage,out side temp aprox.85*
temp kept going up.Made it home put spray on Rad's(a/c,P G tranny cooler.to no avail the press reliefe valve in P.G.poped dumping the red oil on the drive.
car is a 66 w/auto trans,350 engine,new copper replacement radiator....help,2nd time this happened,(the first we were in a parade)no more parades....
Francis

[Rich G.]

Re: newest event overheating AND...

I have a 66 four speed 327/350. When I bought it 10 years ago it had heat issues. The biggest improvement was made by throwing away the copper radiator and buying a DeWitts correct one. Second biggest improvement was getting the timing and advance curve correct with the proper vacuum advance can. (Thanks Duke and the rest of this board.)

Next was replacing the fan clutch with a working one.

Also, using an IR thermometer to tell what the temps really were throughout the system. For example with the bad fan clutch after idling for a while the temp would rise and I noticed the top and bottom hoses were almost the same temp. Not a lot of cooling going on in the radiator. With the new clutch there is about a 30 degree or more difference.

My copper radiator was junk. Maybe yours is better, but I would go for the DeWitts aluminum one.

Rich

[Michael M.]

Re: newest event overheating AND...

Francis, not sure if it's in another thread, but what have you fixed/replaced on the cooling system besides the radiator. Also, does it overheat on the highway or only around town (lots of idling, slow traffic)? Ignition timing can definitely have an effect. Is the engine completely stock or is it modified for more power?

[Francis F.]

Re: newest event overheating AND...

Michael, engine is stock,and yes driving around town,slow traffic and sitting at lights.car has a/c but not operational at this time.the tripple stack of condenser/tranny cooler/and rad.could be cutting down air flow.The clutch fan appears to be engaging..throwing off much heat.
I will get an I R unit and do further checks.Thank Michael/Rich,I will try all...
Francis

[Michael J.]

Re: newest event overheating AND...

I have a 66 four speed 327/350. When I bought it 10 years ago it had heat issues. The biggest improvement was made by throwing away the copper radiator and buying a DeWitts correct one. Second biggest improvement was getting the timing and advance curve correct with the proper vacuum advance can. (Thanks Duke and the rest of this board.)

Next was replacing the fan clutch with a working one.

Also, using an IR thermometer to tell what the temps really were throughout the system. For example with the bad fan clutch after idling for a while the temp would rise and I noticed the top and bottom hoses were almost the same temp. Not a lot of cooling going on in the radiator. With the new clutch there is about a 30 degree or more difference.

My copper radiator was junk. Maybe yours is better, but I would go for the DeWitts aluminum one.

Rich

+1, except all this happened with my '67 427. I always wondered why my '68 428 Cobra Jet Mustang never overheated, then I found this part that Ford put on the engines to solve overheating by changes in vacuum and advance timing:

http://www.428cobrajet.org/id-dist-vac-valve

[William B.]

Re: newest event overheating AND...

Engineer's: Is this possible on a Corvette?

[William C.]

Re: newest event overheating AND...

First check the distributor for proper advance and correct functioning of the vacuum advance. Verify the timing mark on the damper is actually reading TDC. Set the initial timing at 12 degrees at idle with the vacuum advance disconnected. Make sure the vacuum advance is connected to sa full-time manifold vacuum source. Do NOT ASSUME that the distributor advance is functioning correctly without checking it. If equipped with a clutch fan, make sure it is properly functioning. Correct all these and your problems should go away. I had a '65 PG with A/C many years ago, and it could idle forever...

[Clem Z.]

Re: newest event overheating AND...

a lot of old copper/brass rads have the fining coming loose and not making contact with he tube. also rads that were used in areas where salt was used on the roads the contact area become corroded and loosing contact with the tubing .

[William C.]

Re: newest event overheating AND...

I'll also ad that the "new" copper rad isn't likely to be anywhere as efficient as the original aluminum one designed specifically for the Corvette application, but check the easy $$ things first.

[Garry M.]

Re: newest event overheating AND...

Hi Francis,

Just for giggles, check your fan clutch again. It will throw off heat, but not be working properly. Mine failed me and it wasn't obvious at first it was the main problem of overheating, until I turned off the car and saw it continue to spin for a good 15+ seconds. I don't have any official way to test them, other than to say when I took the clutch out, after moving it back/forth several times it started to move quite freely. I also checked for oil around the fan shroud, the front of the engine, and along the hood.

[John H.]

Re: newest event overheating AND...

car is a 66 w/auto trans,350 engine,new copper replacement radiator....help,2nd time this happened,(the first we were in a parade)no more parades....
Francis

Francis -

Your car was born with a highly-efficient Harrison stacked-plate aluminum radiator, probably the best radiator ever made; the "look-alike" copper/brass aftermarket replacements have 30%-40% less cooling capacity (heat rejection capability) than the original radiator. First thing I'd do (after verifying the timing and advance items Bill mentioned) is to call Tom DeWitt and get the correct aluminum stacked-plate reproduction replacement; the radiator you have isn't up to the task.

[Francis F.]

Re: newest event overheating AND...

Clem, can it be said that the engine overheating would cause the pressure relief valve on the powerglide to release trans.fluid ?? thats my secondary problem
Francis

[Edward J.]

Re: newest event overheating AND...

Clem, can it be said that the engine overheating would cause the pressure relief valve on the powerglide to release trans.fluid ?? thats my secondary problem
Francis

Francis, the tube on the top of transmisson is a vent. Not to say pressure in the transmisson will cause fluid to come out the vent. A higher than normal engine temp may cause a rise in pressure in the case. But 215 engine temp. doesn't mean the transmisson is that high. So its likely there maybe a pressure regulator issue internal, but don.t write it off until you do correct the engine temp.

The 215 degrees of temp is not quite a alarm going off, As the car will run at 220 degrees all day without a issue. As it seems all C2/C3 cars are not the same when it comes to engine running temps. there are so many things that we do to make our cars run faster and never look back at the reasons why our cars are now running hotter that the guys c2 next to you.( I.E.cams headers, carburators, dist. assys. that are not set up for normal drivers, but set up for the quarter mile).

Theres some good advise here, radiator, vac. advance. carburator mixture etc.

[Paul J.]

Re: newest event overheating AND...

Francis,

All of this great advice and it seems everyone is missing step number 1 (or did I miss something?) Newer thermostats are designed to fail fully open, but older ones were not. I've seen many fail partially open. This is real fast and simple check. I would do this before I did anything else.

Paul