Engine running hot
Thread Starter
Advanced
Joined: Jun 2004
Posts: 98
Likes: 1
From: tierra verde fl
Engine running hot
Just finished a major restoration on my 63 Convertible. The engine received new radiator (aftermarket direct fit copper/brass), new waterpump and fan clutch (both aftermarket), the only thing added to the engine was power steering. Its a sb base 327 engine and I installed a 160 thermostat to lower the temperature, however she is still running about 220 and after I turn the engine off the thermostat reading rises to 240. This situation is new and was not a problem prior to this restoration effort. Anyone experienced a similar situation? Any ideas? 
Racer
Joined: Feb 2002
Posts: 343
Likes: 1
From: Granger IN
One possible problem is the replacement radiator you used. The copper/brass do not cool as well as the aluminum. Other possible problems are related to engine tuning and vacuum advance.
Check the archives for many discussions on the topic. Others may chime in with more first hand information.
Ryan
Check the archives for many discussions on the topic. Others may chime in with more first hand information.
Ryan
Racer
Joined: May 2001
Posts: 264
Likes: 15
From: San Jose CA
Far and away the most common cause of overheating is the engine timing. I can't speak to the settings you'll need, but a properly working vacuum-advance distributor is critical. Getting it set correctly, with the proper amount of initial advance (again, I don't know what the right settings are for your engine, I'm sure others will chime in) is the key.
Basically, without the proper amount of advance, the combustion flames run too hot, and dump a ton of heat into the engine.
Good luck,
-Brian
Basically, without the proper amount of advance, the combustion flames run too hot, and dump a ton of heat into the engine.
Good luck,
-Brian
Race Director
Joined: Jul 2002
Posts: 11,593
Likes: 173
From: Clayton NC
Lots will tell you replace the radiator but I had a brand new copper brass in mine from when I rebuilt the front end this winter. In less than 100 degree weather in traffic I never got above 220. I was using a Car Quest water pump and a 50/50 coolant mix. So it may not be your radiator but an aluminium one would help. I switched to a DeWitts stock replacement and Stewarts Stage II aluminium water, 160 Robert Shaw thermostat and now adays I never get above 190-200 regardless of how long I sit in traffic. With it being cool out now I may have to switch to a 180 thermostat just she will warm up a little quicker.
As stated above it could be your timing. However could you tell us whether the temp jumps when going down the road or when sitting? ... Dave..
As stated above it could be your timing. However could you tell us whether the temp jumps when going down the road or when sitting? ... Dave..
Race Director
Joined: May 2000
Posts: 12,712
Likes: 2,270
First, a lower temperature themostat WILL NOT cure or preclude overheating. The thermostat establishes the LOWEST operating temperature. The highest is established by radiator heat transfer capacity and air flow, and Corvettes received premium cooling system components such as the aluminum radiator and themomodulated fan clutch to ensure proper cooling of what is a big engine in a small car.
The first advice to all is to always used OE or OE equivalent cooling system components. Many have found that "replacement" copper brass radiators DO NOT provide sufficient cooling and results in hot running.
What kind of "aftermarket" fan clutch? Make? Part number? Is is supposed to be a direct replacemnet for the original?
Also check for proper function of the vacuum advance against specs in the shop manual, and ensure that the manifold vacuum signal line shows full manifold vacuum at all times including idle.
If would also help diagnosis if you would be more specific on when the car overheats: Idle and low speed driving? Cruising at highway speed? All of the above?
Duke
The first advice to all is to always used OE or OE equivalent cooling system components. Many have found that "replacement" copper brass radiators DO NOT provide sufficient cooling and results in hot running.
What kind of "aftermarket" fan clutch? Make? Part number? Is is supposed to be a direct replacemnet for the original?
Also check for proper function of the vacuum advance against specs in the shop manual, and ensure that the manifold vacuum signal line shows full manifold vacuum at all times including idle.
If would also help diagnosis if you would be more specific on when the car overheats: Idle and low speed driving? Cruising at highway speed? All of the above?
Duke
Melting Slicks
Joined: Apr 2002
Posts: 2,620
Likes: 0
From: 20 forward gears to shift through in MD
Originally Posted by SWCDuke
First, a lower temperature themostat WILL NOT cure or preclude overheating. The thermostat establishes the LOWEST operating temperature. The highest is established by radiator heat transfer capacity and air flow, and Corvettes received premium cooling system components such as the aluminum radiator and themomodulated fan clutch to ensure proper cooling of what is a big engine in a small car.
The first advice to all is to always used OE or OE equivalent cooling system components. Many have found that "replacement" copper brass radiators DO NOT provide sufficient cooling and results in hot running.
What kind of "aftermarket" fan clutch? Make? Part number? Is is supposed to be a direct replacemnet for the original?
Also check for proper function of the vacuum advance against specs in the shop manual, and ensure that the manifold vacuum signal line shows full manifold vacuum at all times including idle.
If would also help diagnosis if you would be more specific on when the car overheats: Idle and low speed driving? Cruising at highway speed? All of the above?
Duke
The first advice to all is to always used OE or OE equivalent cooling system components. Many have found that "replacement" copper brass radiators DO NOT provide sufficient cooling and results in hot running.
What kind of "aftermarket" fan clutch? Make? Part number? Is is supposed to be a direct replacemnet for the original?
Also check for proper function of the vacuum advance against specs in the shop manual, and ensure that the manifold vacuum signal line shows full manifold vacuum at all times including idle.
If would also help diagnosis if you would be more specific on when the car overheats: Idle and low speed driving? Cruising at highway speed? All of the above?
Duke
with Duke. Also, have you verified the actual operating temperature with an IR gun? If not you may also want to verify that the sending unit is giving you the correct reading... 
Thread Starter
Advanced
Joined: Jun 2004
Posts: 98
Likes: 1
From: tierra verde fl
Thanks for all the advice, to answer a few questions;
The engine runs hot at highway speed only, not at idle.
The fan clutch was bought at NAPA and was listed as a replacement for 63 Corvette 327 sb engine, its diamater is much bigger than the original one which was faulty.
What I also don't understand that the temparature heating goes up to 240 after the engine has been turned off, then its extremely hard to start at that temparature. Need to wait until it cools down to restart.
Has anyone installed a electric fan in place of the fan clutch? Results?
The engine runs hot at highway speed only, not at idle.
The fan clutch was bought at NAPA and was listed as a replacement for 63 Corvette 327 sb engine, its diamater is much bigger than the original one which was faulty.
What I also don't understand that the temparature heating goes up to 240 after the engine has been turned off, then its extremely hard to start at that temparature. Need to wait until it cools down to restart.
Has anyone installed a electric fan in place of the fan clutch? Results?
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Burning Brakes
Joined: Mar 2004
Posts: 1,108
Likes: 4
From: Plano Texas
Along with everything Duke suggested, your highway hot-running temp suggests three things to consider:
1. collapsed lower radiator hose; is there a coiled wire in it?
2. improper vacuum advance and timing;
3. inadequate air flow through the radiator; gaps around the radiator?
Try looking at these first. Good luck.
1. collapsed lower radiator hose; is there a coiled wire in it?
2. improper vacuum advance and timing;
3. inadequate air flow through the radiator; gaps around the radiator?
Try looking at these first. Good luck.
Team Owner
Joined: Oct 2000
Posts: 38,897
Likes: 1,926
From: Washington Michigan
Originally Posted by karista
Thanks for all the advice, to answer a few questions;
The engine runs hot at highway speed only, not at idle.
The fan clutch was bought at NAPA and was listed as a replacement for 63 Corvette 327 sb engine, its diamater is much bigger than the original one which was faulty.
What I also don't understand that the temparature heating goes up to 240 after the engine has been turned off, then its extremely hard to start at that temparature. Need to wait until it cools down to restart.
Has anyone installed a electric fan in place of the fan clutch? Results?
The engine runs hot at highway speed only, not at idle.
The fan clutch was bought at NAPA and was listed as a replacement for 63 Corvette 327 sb engine, its diamater is much bigger than the original one which was faulty.
What I also don't understand that the temparature heating goes up to 240 after the engine has been turned off, then its extremely hard to start at that temparature. Need to wait until it cools down to restart.
Has anyone installed a electric fan in place of the fan clutch? Results?
Heating at highway speeds but not in town generally says the radiator is inadequate, assuming the rest of the cooling system is operating properly and your advance system (vacuum and centrifugal) is set up correctly. Copper/brass replacement radiators have about 30%-40% less heat rejection capability than the original Harrison stacked-plate aluminum radiator, and are a poor place to save money.
It's perfectly normal for engine temperature to go up after shutdown - that's "heat-soak". When you say it's difficult to re-start when hot, what is the symptom? Won't crank? Cranks slowly? Cranks but won't fire? Flooded?
Electric fans are unnecessary - just a band-aid for a basic cooling system problem, and they won't help at all on the highway; airflow isn't an issue at highway speed - only radiator efficiency.
Racer
Joined: Sep 2004
Posts: 327
Likes: 0
From: Conroe TX
Race Director
Joined: Apr 1999
Posts: 10,866
Likes: 717
From: Beverly Hills/Pine Ridge Florida
Nobody's actually said it, but IF it's your timing, it's because it's too retarded. Cars with the timing too retarded will run hot. This could be related to initial timing or to centrifugal/vacuum advance.
You state you did a major restoration to your 63 convertible. What if anything did you do to the engine? Rebuilt? Bored? Heads? etc. Chuck
You state you did a major restoration to your 63 convertible. What if anything did you do to the engine? Rebuilt? Bored? Heads? etc. Chuck
Former Vendor
Joined: Jan 2000
Posts: 5,593
Likes: 631
From: Brighton
If you're looking for good advice, re-read SWCDuke and John Z comments. This is where to start!
You could also look at hundreds of archive posts where people have downgraded with a c/b radiator, only to find out they run hot. You're not the first and not the last to do this, we see it all the time. Real test data shows that the c/b rads are 30% below the GM aluminum specs, so if you cut 1/3 of your radiator off and it ran hotter would you wonder why?
You might have some other issues too, maybe the temp sending unit is off, and maybe the timing is off, but in the end the c/b radiator has to go.
You could also look at hundreds of archive posts where people have downgraded with a c/b radiator, only to find out they run hot. You're not the first and not the last to do this, we see it all the time. Real test data shows that the c/b rads are 30% below the GM aluminum specs, so if you cut 1/3 of your radiator off and it ran hotter would you wonder why?
You might have some other issues too, maybe the temp sending unit is off, and maybe the timing is off, but in the end the c/b radiator has to go.
