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78 runs too hot

 
Old 01-16-2019, 12:26 AM
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Penelopegirl
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Default 78 runs too hot

My 78 has a 383 stroker crate engine and Upgraded aluminum radiator with electric fans. After an 18 month upgrade inside and out shes running beautiful but shes running hot. Heats quickly to 190-195 and 200. Mechanic reworked the fans and replaced the switch as they were not coming on. Ordered a new thermostat. Today I had her out and up to 225-230 by the time I got home. So not steaming but a bit of diesel when I switched ignition off. Just looking for other experience with these electric fans. What size are you using? These temps in line? Im old school and they just feel way too hot for me. Appreciate any incite you can add without the insults please. I do have a competent mechanic but hes a general guy and Im hoping you guys have more specialty that can help.
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Old 01-16-2019, 01:07 AM
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https://willcoxcorvette.com/corvette...am-stock-73-79

Do you have this spoiler in front?
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Old 01-16-2019, 07:33 AM
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jb78L-82
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Assuming everything is in great shape, radiator (aluminum preferred), water pump, seals, fan (s), spoiler extension and 79 Heavy duty spoiler referenced above from Willcox, I was going to suggest timing and then I saw you mentioned dieseling...Retarded timing will make the engine run VERY hot. Also, which heads are on the engine? My guess is timing...or thermostat.......Do you have a robertshaw thermostat with a 3/16 by pass hole drilled in the thermostat base?Are you certain that the aftermarket electric fans are not interfering with airflow at speed....Personally, I would go with a heavy duty GM multiblade mechanical fan with a thermostatic clutch on a C3 but just me....

Last edited by jb78L-82; 01-16-2019 at 07:37 AM.
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Old 01-16-2019, 08:53 AM
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Do you have an IR thermometer? Take a temp off the upper radiator hose to confirm your instrument.

Last edited by Bikespace; 01-16-2019 at 08:55 AM.
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Old 01-16-2019, 10:04 AM
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Penelopegirl
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Originally Posted by Peterbuilt View Post
Is this an add on verse replace? Can you explain the benefits?
Im a software consultant so I’m just learning a lot of mechanical stuff. I appreciate your patience. Thanks! ��

Last edited by Penelopegirl; 01-16-2019 at 10:37 AM.
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Old 01-16-2019, 10:20 AM
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Originally Posted by jb78L-82 View Post
Assuming everything is in great shape, radiator (aluminum preferred), water pump, seals, fan (s), spoiler extension and 79 Heavy duty spoiler referenced above from Willcox, I was going to suggest timing and then I saw you mentioned dieseling...Retarded timing will make the engine run VERY hot. Also, which heads are on the engine? My guess is timing...or thermostat.......Do you have a robertshaw thermostat with a 3/16 by pass hole drilled in the thermostat base?Are you certain that the aftermarket electric fans are not interfering with airflow at speed....Personally, I would go with a heavy duty GM multiblade mechanical fan with a thermostatic clutch on a C3 but just me....
No I do not have that thermostat and I do not have that spoiler. The slight diesel was only when the temp was 225-230 and never happens at lower temps so I felt it was temp related verse timing... could be wrong. I’m a software consultant so I’m just trying to get as much information as I can to be sure this problem gets fixed quickly because I’m already into rework. Thank you.
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Old 01-16-2019, 12:02 PM
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Above is the 79 ONLY option, L-82's with heavy duty cooling^^^^^^^^^^^^^^^^^^. It is VERY effective keeping the temps down at speed. My C3 is a 78 L-82 4 speed car with gymkhana suspension in which I purchased the 79 spoiler extension from a local Chevy dealer in the early 90's.............and installed it myself after seeing it on a 79 L-82 at a car show at that time.

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Old 01-16-2019, 12:45 PM
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The biggest contributor to hot running is retarded timing. Make sure your initial timing is in the high 'teens and that you're running 34 total (if you have aftermarket heads - 36 total with stock iron heads). Make darned sure you are running a vacuum advance hooked up to manifold vacuum, and that the vacuum advance is limited to pulling in 10-12 degrees, thus giving you actual timing at idle of about 30 degrees and actual timing at cruise in the mid-40's. If you are not hitting these numbers, you will run hot.

Lars

Last edited by lars; 01-16-2019 at 12:46 PM.
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Old 01-16-2019, 12:54 PM
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Either you or have your mechanic burp your cooling system.
You could have air trapped in your engine, which is a common occurrence on Corvettes when a new engine is installed.
There are several threads on the proper procedure to do this and it really needs to be done.
A small hole drilled in the thermostat will help once the engine is burped of any trapped air.
If I remember correctly, it occurs because the coolant passages in the intake manifold are higher than the coolant level of the radiator.

Another common overheating factor on Corvettes is that the lower radiator hose is missing the required spring, which allows the hose to collapse while driving and restricts coolant flow.
Good luck and keep us posted.
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Old 01-16-2019, 01:36 PM
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Post SEVERAL pictures of your engine compartment so folks can eyeball it. You'd be amazed at the observation capabilities of some of the folks on this forum. Make sure to get several of the radiator, fans, water pump, belts, front spoiler area, etc.

Originally Posted by Penelopegirl View Post
My 78 has a 383 stroker crate engine and Upgraded aluminum radiator with electric fans. After an 18 month upgrade inside and out shes running beautiful but shes running hot. Heats quickly to 190-195 and 200. Mechanic reworked the fans and replaced the switch as they were not coming on. Ordered a new thermostat. Today I had her out and up to 225-230 by the time I got home. So not steaming but a bit of diesel when I switched ignition off. Just looking for other experience with these electric fans. What size are you using? These temps in line? Im old school and they just feel way too hot for me. Appreciate any incite you can add without the insults please. I do have a competent mechanic but hes a general guy and Im hoping you guys have more specialty that can help.
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Old 01-16-2019, 01:52 PM
  #11  
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Originally Posted by Penelopegirl View Post
Is this an add on verse replace? Can you explain the benefits?
Im a software consultant so Im just learning a lot of mechanical stuff. I appreciate your patience. Thanks! ��
The front 'air dam' (spoiler) was stock and forces the air up into the radiator.
https://keenparts.com/CorvettePartsD...&diagram=42011

Do you have a shroud that fits around the fan and is the radiator sealed around the sides with the stock rubber gaskets?

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Old 01-16-2019, 02:29 PM
  #12  
karol
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this is a close up of the extension JB78L wrote about. It lowered my temps during highway driving, but find out first if you engine is operating correctly. You might not need the extension which you can put on later but the factory spoiler is there for a purpose:

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Old 01-16-2019, 03:15 PM
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Originally Posted by Peterbuilt View Post
The front 'air dam' (spoiler) was stock and forces the air up into the radiator.
https://keenparts.com/CorvettePartsDiagrams.php?year=ALL&diagr am=42011

Do you have a shroud that fits around the fan and is the radiator sealed around the sides with the stock rubber gaskets?
This! The electric fan has to be sealed, really well, flush and tight to the radiator. If you don't have a seal around the circumference of the fan shroud, then the air, is going to be pulled in around the open edges (because it's easier), than being pulled through the radiator. The seal forces the electric fan, to pull through the radiator. When we initially installed my electric fans, my buddy held up a little strip of paper, close to the unsealed edge, while it was running and the end of that paper, got sucked right into the empty gap between the shroud and the radiator. Air is lazy! It will go the easy route first.

PS: I don't have a lower extension on my '74 (didn't come with one) and it hasn't overheated yet. It might be of help for sure, but not a necessity (IMHO).

Last edited by F22; 01-16-2019 at 03:16 PM.
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Old 01-16-2019, 03:22 PM
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jb78L-82
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Just to be clear, the 79 only optional spoiler extension is NOT a requirement for normal operating temps, just it will help lower the temp when the car is moving, beyond the factory chin spoiler. GM came up with the 79 only option for a GOOD reason.

Also, the electric fans, mechanical fans, any fan should have zero influence on the operating temps when the car is moving above 35 mph...no effect.If the fans operate when the car is movong at speed to keep the temp normal, there is another issue that needs to be addressed

Last edited by jb78L-82; 01-16-2019 at 03:28 PM.
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Old 01-16-2019, 06:29 PM
  #15  
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Hi Guys. I should have included more info up front but here goes. The car was bought in 1992 for my husband and was his. He took it to a performance shop that did the 383 and some other performance work. He became ill after that. He died suddenly in 2016 and the car became my baby. Now I know very little of her history and Im a software consultant so Im not mechanical. 2017 I took on the project to redo the interior in black and put back the air conditioning as you know Florida gets hot. Haha. The info Ive spouted is from my mechanics who are finishing up as we found putting the air back was more complicated than I thought plus some upgrades.
So
i have a spoiler which I believe is factory see picture.
Ill take pictures.
Theres no shroud. And
im sharing all your great suggestions with both of them. So thank you.
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Old 01-16-2019, 07:26 PM
  #16  
resdoggie
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Originally Posted by jb78L-82 View Post
Just to be clear, the 79 only optional spoiler extension is NOT a requirement for normal operating temps, just it will help lower the temp when the car is moving, beyond the factory chin spoiler. GM came up with the 79 only option for a GOOD reason.

Also, the electric fans, mechanical fans, any fan should have zero influence on the operating temps when the car is moving above 35 mph...no effect.If the fans operate when the car is movong at speed to keep the temp normal, there is another issue that needs to be addressed
Is that extension available anywhere now do you know?
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Old 01-16-2019, 07:38 PM
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Originally Posted by resdoggie View Post
Is that extension available anywhere now do you know?

I believe Willcox makes a reproduction.................
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Old 01-16-2019, 07:41 PM
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Originally Posted by resdoggie View Post
Is that extension available anywhere now do you know?
That's a dead animal scraper.
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Old 01-16-2019, 07:44 PM
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Originally Posted by jb78L-82 View Post
I believe Willcox makes a reproduction.................
Just googled. CC has them. Thanks.

Edit: It's Zip that has them. Not sure about CC.

Last edited by resdoggie; 01-16-2019 at 07:50 PM.
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Old 01-16-2019, 07:45 PM
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Originally Posted by HeadsU.P. View Post
That's a dead animal scraper.
Does it work for moose and deer?
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