Overheating is an Understatement
 

I’m running a numbers matching rebuilt 327/365hp motor in my ’64 coupe that is consistently overheating. Heading out on a drive I start with a 5 min drive to the highway and cruise at 60 mph. 15 min after that the needle climbs over 210 deg. This isn’t an issue of simply running hot, because it will continue over 210 if I don’t stop and it’s hard to completely enjoy a car that has a 20 min driving range. The temp grows consistently and only once did I let it go over 210 deg to puking (240+). That was a mistake I’ll only make once so to protect this motor.

I have gone through all the FAQ and Sticky threads on this forum and am at a dead end. References are listed in the links at the bottom for what I read through. The most helpful was John Hinckley’s article titled “Early Corvette Cooling”.

To follow Mr. Hinckley’s checklist:
Coolant – 50/50 mix with Water Wetter
Radiator – 6 years old aluminum Griffin that has been flushed regularly, is clean of debris, and has good flow. 20 deg of cooling when idling in garage (180 top, 160 bottom)
Expansion Tank – Filled exactly half way to the “Fill Cold” line
Water Pump – High flow replacement
Thermostat – New, tested 160 deg. (I know 160 vs. 180 is irrelevant)
Radiator Cap – 16# (13# used with same result)
Lower Radiator Hose – New and reinforced
Fan Shroud and Seals – All stock and accounted for
Fan and Clutch – Clutch fan working properly. Replaced with solid racing fan and got same result. Half-in/half-out
Temperature Gauge and Sending Unit – Verified accurate with IR gun
Ignition Timing – Total timing set to 34 deg results with a base timing of 12 deg. Less advanced timing provided the same result in temp.
Engine Bore – 4.06” diameter

I’ve had the car for two weeks and would like to “watch the scenery while cruising instead of the temperature gauge” so any input is much appreciated.

Thanks,
John

Reference material:
Overheating / Cooling FAQ - http://forums.corvetteforum.com/1558302870-post3.html
Barry and Linda’s Vette Tech Section - http://lbfun.com/Corvette/Tech/vettetech.html
Still boiling hot but there is light. - http://forums.corvetteforum.com/c1-a...post1561445673
66 corvette over heating - http://forums.corvetteforum.com/c1-a...r-heating.html

The car did puke the one time he let it go above 210 as indicated in the first post - he has a genuine overheating problem - not faulty instrumentation IMO. He also verified readings with I/R temp gun.

OP has done all the logical, correct things to troubleshoot. I'll be interested to see what others may say on the topic.

"The temp grows consistently and only once did I let it go over 210 deg to puking (240+)."

Were you pulled over and stopped, or driving when this happened..??

EDIT BELOW


Kind of a dumb question...your heater core..is it new and free of blockage...do you have your hoses on correctly...

What's the build history on the motor? Fresh rebuild, recent rebuild, or original? What coolant was in it when you bought it? Aluminum or cast pump? Aluminum or original heads? See my post on the 66 overheating big block - excessive corrosion build up. If all else has been ruled out, a blockage is likely.

IMHO I would add the following to the list:

Run a distributor vacuum advance, (if your not already), this will help
Remove the two block drain plugs and power flush the block
50/50 mix of distilled water and antifreeze

This should be an interesting post...

Does your griffin rad have tanks on each end? If so,That might be your problem!

As soon as your griffin goes under load, it can't handle the extra BTUs.:mad:

Get a proper exact re-production radiator from DeWitts. That will cure it. $700-900 Later.:thumbs:

Elaborate more on High Flow pump.

I have found the best pumps are GM factory, or NAPA replacement pumps. The after-market performance pumps seem to not flow water well at low RPM. Not sure what RPM range your overheating is in

Doug

You didn't mention if this was a new build, or if the problem has always been there, or if it just started. The overbore isn't helping, but .060" shouldn't be too much

Doug

Ya, the "high flow" can pump coolant so fast it doesn't have time to do a heat exchange.

"Temperature Gauge and Sending Unit – Verified accurate with IR gun"

No question is a dumb question at this level of desperation.

I have not looked into the heater core or hoses. I'll check it when I get home, but it sure pumps out hot air well when I'm trying to keep the temp low.

bypass it for now and check. Correct? Did you check to see if there is any fuel in the water? Or anything coming out the tailpipes?

I'm already running a distributer vacum advance, but just in case will double check it's functionality.

I'm already running a distributer vacuum advance, but just in case will double check it's functionality.

There are bulges on each end that may be the tanks you're describing.

It's a painted versio of this:
http://www.griffinrad.com/images/rad_images/6-00061.jpg

I don't know much about the pump. The only reason I know it's high flow is because it says so on the engine rebuild docs.

I'm overheating in all rpms. Idle in the garage up to cruising at 80 mph (3k ish).

The motor was rebuilt in 2001 but non of the documentation indicates the mileage. Somewhere between 32k and 60k isn't the best indicator.

I've heard of that and it made me wonder.

If it's idling and not even driving, wouldn't a drop in temp from 180 to 160 be a good indicator of the heat exchange rate? 20 deg isn't great but I wouldn't think it's all that bad for sitting in a hot garage with minimal air flow.

Bypass is a good idea to eliminate one more possible issue.

When I flushed the coolant there was no fuel or oil in it.

Exhaust looks good too. Maybe running a bit rich, but that's better than lean for heating issues.

If after you troubleshoot your problem it leads to your radiator this is the best place to go:

http://www.dewitts.com/collections/c...inum-radiators

Dennis