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.
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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... |
Originally Posted by tebok
(Post 1584361935)
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) 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 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.
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Originally Posted by Kerrmudgeon
(Post 1584362011)
If the car's not acting funny...gurgling, steaming, or spewing, I'd suspect the gauge or sender unit. Check it with an infrared meter on thermostat housing and other parts of the motor before you start messing with the motor.:thumbs:
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Originally Posted by 66jack
(Post 1584362136)
"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... 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. |
Originally Posted by tebok
(Post 1584362423)
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. |
Originally Posted by SS409
(Post 1584362302)
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... |
Originally Posted by SS409
(Post 1584362302)
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... |
Originally Posted by MiguelsC2
(Post 1584362304)
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: It's a painted versio of this: http://www.griffinrad.com/images/rad_images/6-00061.jpg |
Originally Posted by AZDoug
(Post 1584362314)
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 I'm overheating in all rpms. Idle in the garage up to cruising at 80 mph (3k ish). |
Originally Posted by AZDoug
(Post 1584362332)
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 |
Originally Posted by MiguelsC2
(Post 1584362341)
Ya, the "high flow" can pump coolant so fast it doesn't have time to do a heat exchange.
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. |
Originally Posted by jimh_1962
(Post 1584362448)
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?
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 |
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