68 Hot Corvette

[lljr97]

I recently replaced the engine in my corvette with a .030 over 350. In the process I had my radiator flow tested and it was said to be OK. Ever since I have had a problem with the temp going as high as 200 degrees. I changed the thermostat from 180 to 160 and removed it altogether. To no avail. I have been told to replace the radiator with an aluminum one or get puller fans but I would appreciate some advice. If anyone has any ideas I would like to hear from you.

 

[Ken]

You should never run without a thermostat; it's part of the cooling system design. :nono

 

[69autoXr]

If my car ever only reached 200, I think I'd be ecstatic. Why do you think there's a problem with 200 degrees? It's not going to run 160 with a 160 thermostat no matter what you do.

 

[ArkShark]

http://community-2.webtv.net/MATTGRU/doc/index.html

I found this link on another corvette site I visit.
Good ideas in there....

Be sure to read the note after #10....

BTW, my '77, with headers, now gets to about 190F....

 

[BeaterShark]

I agree that 200 is not hot. In fact, I have electric fans that do not come on until 200*.

Anytime the engine is running hotter than the temp at which the thermostat opens, using a cooler thermostat will only prolong the time it takes to reach that tempature.


I wouldn't worry about it.

 

[68Roadster]

My 68 hits 200 easy......68's aren't known for being great water coolers, first year body style problems if I read the history book right.

I say press on!

 

[JohnZ]

1. Verify what your temp gauge is telling you by shooting the radiator hose where it exits the thermostat housing with an I.R. gun so you know whether the gauge is accurate (most aren't, especially if the sending unit has been replaced). You may not have a problem at all.

2. How old is your radiator? If it's original, it's lost at least 30%-40% of its cooling capacity over the years due to scale accumulation in the tubes; the "flow test" doesn't tell you anything about the radiator's heat rejection capability - only that it isn't plugged. If the radiator has been replaced, is it the equal of the original in actual cooling capacity, or was it bought on "price"?

3. Are the correct fan shroud and fan clutch still in place? They're essential to idle and low-speed traffic cooling, with the tips of the fan blades located half-in/half-out of the rear edge of the shroud, and the shroud should be sealed to the radiator.

4. Put the 180* thermostat back in - it modulates coolant flow and has nothing whatsoever to do with operating temperature; it only determines MINIMUM operating temperature, like in the winter.

5. Check your timing and vacuum advance operation; retarded timing and inoperative vacuum advance are major contributors to heating.

6. Is your lower front air dam still in place? Your Corvette is a "bottom-breather", and will definitely heat up on the highway without the air dam in place to deflect airflow up through the radiator.

7. Are all of your original rubber radiator-to-support seals still in place? If not, that's allowing incoming air to bypass the radiator core instead of being forced through the core to carry off heat from the radiator.

99% of cooling problems are related to not enough radiator cooling capacity, airflow management through the radiator, ignition timing, or combinations of those issues. The original cooling system (especially on small-blocks) was perfectly adequate; attempts to "re-engineer" it usually fail miserably (although they enrich the folks at Jeg's and Summit).

 

[68Roadster]

John,
That brings up an interesting question. My 68 has no lower front air dam. Looking at the fibreglass work under there I can't see that it ever has. Is this something peculiar to an Oct '67 built car?? I do have the 2 holes cut out which was supposedly rescinded (according to my AIM).....I have never seen the air dam in the AIM either....

Thanks for the insight.

 

[FLATOUT427]

i have an early '68 and it has an air dam.

 

[68Roadster]

FO427,
I knoe they make them but I can't find it in the AIM so I'm thinking it's aftermarket....driving me crazy now.....

 

[lljr97]

You should never run without a thermostat; it's part of the cooling system design. :nono

Thank you for the info. I will reinstall the 180 thermostat and run it.

 

[lljr97]

If my car ever only reached 200, I think I'd be ecstatic. Why do you think there's a problem with 200 degrees? It's not going to run 160 with a 160 thermostat no matter what you do.

Thank you for the reply. I guess I panicked with seeing the temp at what I thought was high. I am reinstalling the 180 thermostat and will run it. I have some other things to check also.

 

[lljr97]

1. Verify what your temp gauge is telling you by shooting the radiator hose where it exits the thermostat housing with an I.R. gun so you know whether the gauge is accurate (most aren't, especially if the sending unit has been replaced). You may not have a problem at all.

2. How old is your radiator? If it's original, it's lost at least 30%-40% of its cooling capacity over the years due to scale accumulation in the tubes; the "flow test" doesn't tell you anything about the radiator's heat rejection capability - only that it isn't plugged. If the radiator has been replaced, is it the equal of the original in actual cooling capacity, or was it bought on "price"?

3. Are the correct fan shroud and fan clutch still in place? They're essential to idle and low-speed traffic cooling, with the tips of the fan blades located half-in/half-out of the rear edge of the shroud, and the shroud should be sealed to the radiator.

4. Put the 180* thermostat back in - it modulates coolant flow and has nothing whatsoever to do with operating temperature; it only determines MINIMUM operating temperature, like in the winter.

5. Check your timing and vacuum advance operation; retarded timing and inoperative vacuum advance are major contributors to heating.

6. Is your lower front air dam still in place? Your Corvette is a "bottom-breather", and will definitely heat up on the highway without the air dam in place to deflect airflow up through the radiator.

7. Are all of your original rubber radiator-to-support seals still in place? If not, that's allowing incoming air to bypass the radiator core instead of being forced through the core to carry off heat from the radiator.

99% of cooling problems are related to not enough radiator cooling capacity, airflow management through the radiator, ignition timing, or combinations of those issues. The original cooling system (especially on small-blocks) was perfectly adequate; attempts to "re-engineer" it usually fail miserably (although they enrich the folks at Jeg's and Summit).

Thank you for the lengthy and very informative reply. I guess I have more to check and now I know all of the factors that can contribute to this issue. Again, Thank you for your help.

 

[lljr97]

My 68 hits 200 easy......68's aren't known for being great water coolers, first year body style problems if I read the history book right.

I say press on!

Thank you for the info. I had no idea of the norma operating temperature but with you guy's help I feel more comfortable with the temperatures.

 

[BeaterShark]

i have an early '68 and it has an air dam.

Does it divert air through the radiator?

I guess you could say that my '69 has an air dam, but the only way air can get to the radiator is through the front grills.

I think at some point later in the shark years ('73??), they went with a different front valence panel which allowed airflow from the bottom.

 

[lljr97]

http://community-2.webtv.net/MATTGRU/doc/index.html

I found this link on another corvette site I visit.
Good ideas in there....

Be sure to read the note after #10....

BTW, my '77, with headers, now gets to about 190F....

Thank you for the great link. The information will be very usefull in aiding me with the issue. Also saving me lots of money stopping me from buying parts un- necessarily.

 

[GTR1999]

Check to be sure your gauge is accurate. My 69 would stay right on the line before 210. If it hit 210 it was running above normal. I checked the gauge against a calibrated digital thermometer and it was right on.

As stated, check the seals on the radiator and shroud, clutch fan, timing, radiator cap and radiator general condition, carb mixture-if too lean it will run hot. I also added a "FlowKooler" impellar to the water pump to increase flow. Don't bother with the water wetter stuff it was a waste of money in my case.

Where in CT are you located?

 

[lljr97]

Check to be sure your gauge is accurate. My 69 would stay right on the line before 210. If it hit 210 it was running above normal. I checked the gauge against a calibrated digital thermometer and it was right on.

As stated, check the seals on the radiator and shroud, clutch fan, timing, radiator cap and radiator general condition, carb mixture-if too lean it will run hot. I also added a "FlowKooler" impellar to the water pump to increase flow. Don't bother with the water wetter stuff it was a waste of money in my case.

Where in CT are you located?

I went to edelbrock.com to get the exact fuel mixture setting procedure and will make sure it is right. I live in Middletown, Ct. Are you close to that?
Thanks for the response.

 

[GTR1999]

Yeah, I'm not far from you. I'll send you a private message.