Vette-kid

I have a78 that i have rescued and after nearly 6 years out its finally running and driving! It does ok keeping cool in town ( around 200 on the guage...not verified yet). But on the highway it climbs to about 230 ( and more if i let out getting in rpm). I'm convinced it will do great once i get all of the foam seals in place and the front spoiler on ( need find one first). Can someone give me a good pic of the frog spoiler and valance on a 78 non pace car? I'm missing both and would like to see what it is supposed to look like under there ( assembly manual is not very helpful). Thanks in advance.

SLVRSHRK

Are you looking for the stock spoiler or the Pace Car spoiler?

I have the PC spoiler on my SA.

Vette-kid

Stock i suppose. Any real advantage, cooling wise, if i were to use a pace car spoiler? Anything aftermarket that works better? This car is not stock so that doesn't matter. What ever will work best.

DUB

I would install the stock NON pace car design front air dam. That will give you a 'feel' if it helped you out on the temperature issue. Installing this design air dam is pretty straight forward when you get it.

AND...I can 'say'...that the foam seals BETWEEN your radiator and radiator support are VERY IMPORTANT.....along with all others in conjunction with the stock fan shroud also.

The front air dam is more than likely going to help greatly.

And if you concerned about the engine coolant temperature....because it is getting higher than you like. when I get Corvettes in my shop with this concern from the owner...I install my racing temp gauge that is much more precise and check it and see if what I get on my gauge is the same as what the original gauge is showing. Sometimes it is NOT getting as hot as the factory gauge is showing....due to a problem in the sending unit.

DUB

Vette-kid

Thanks. I do need typ verify the temps, but also need to do the foam and spoiler anyway. I'm using a Volvo electric fan with a shroud that seals well against the radiator. Rad is a 3 core aluminum champion. My car was a basket case and did not have the stock radiator or shroud with it anyway.

cagotzmann

I think you may have something else not working. When I replaced the L48 engine with a ZZ383 I went with a serpentine kit. So the stock clutch fan / shroud was removed. I also remove the front spoiler kit ( stock 78 pace car look repainting.)

I have a dewitts alum. radiator. So before I finshed all items I would test drive the car. (75 outside air temp )

So without a spoiler or clutch fan / shroud and only air flow while driving. I never had any heat problems while the car was moving. Higher temps in city driving vs highway driving. 180 degree thermostat. Run about 180-190 city and stayed a cool 180 on the highway.

I then added dual spal electric fans. Still on the highway they never come on, The only time they run is when the car is sitting at idle.

Then I added the spoiler back again no change while driving. The fans never come on.

I would question the ability of your radiator to cool the fluid.

If you can test the temp of the upper hose vs the lower hose to see how well the radiator can cool the fluid.

Vette-kid

Possible, but I have NO foam seals installed yet. So any air flow likely is going around the radiator itself other than what the fan draws through it. And while the temp is high...I'm not boiling over yet. Since this is my first time putting together a car, i count that as a win!

cagotzmann

Are you taking about the foam seal at the top of the radiator. Just use some duct tape as a test.

This is the only seal I have installed and its only partially. Nothing along the sides at all.

There should be pletty of air flow at highways speed to keep things cool. Does the car have A/C ? and is the condensor in front of the radiator clean and allowing air flow ?

The other items is to check if the water pump is actually moving fluid.

Run the engine with the rad cap off and watch how much flow you get when the thermostat opens ?

Vette-kid

No AC right now. I am talking about all the seals. There are some on top that seal the hood, and some on the side that seal to the radiator support.

It is flowing fine i believe. It stays cool in town pretty well. My theory is that at highway speeds with sustained high rpm (3200ish) there is not enough air over the radiator to keep up. The lack of spoiler tho divert air up there and lack of seals creating a path of least resistance around the radiator are the likely culprit.

I'd still live to see a good pic of a stock spoiler and valance installed.

Cooter Tech

I had the same problem on my 78 without spoiler. I could drive it all day on surface streets with no overheating problems. When I got on the freeway if would start to overheat. I installed spoiler and it solved the problem with overheating on freeway. Cheap easy fix too and it made a big difference.

DUB

YES...the foam seal to aid in sealing the hood to the radiator support does help.

Verifying your coolant temps would be wise as you know.

How long are you driving at 3200ish RPM's????

And when you get back down to inner city speeds...does the temp gauge fall to where you feel better about it????

I am wondering if the timing and or fuel delivery (running lean) is also a part of this equation. Not meaning to be 'snippy'...but your initial post had nothing about an electric fan, aluminum radiator ,etc. So I assumed it was stock set-up. Is there anything else that you have done that you may be leaving out that can remotely be considered as a part of this problem??? Some times it is the small things that cause a BIG problem.

DUB

BKarol

Back in 79 they offered an additional air deflector extension. (See pic once posted by KapsSA). I have a 78 and ran into the same problem. Stock fan & shroud & radiator. Around town no problem but once on the highway the temp went over 200. I have 3.70 rearend so was always around 3400rpm. Get on the off ramp and temps came down. I put in seals but this extra extension which provides an extra 2 inches of spoiler is what brought my temp down to 200 on the highway. Definitely needs a spoiler even if just the original.

Vette-kid

DUB, thanks for the input. I did not include it originally because i was really just trying to get information on the spoiler, not really diagnose the problem further. I am convinced the spoiler and seals are my problem. All that said, i absolutely appreciate all the info you have provided. You have been instrumental in getting my car this far as you have given Kerry advise on several threads i have posted asking the way.

Engine is a 383 stroker on a full roller block. Alum radiator Volvo 2 speed fan with bmw dual temp switch. Switch is in the upper radiator hose (probably not ideal, but easiest way to a dual temp switch). Both speeds are working switch is 190/205 if i remember correctly. I'll have to verify that, i think they make a lower one as well. Once i get the seals and spoiler installed i will test again and revisit the switch and its location if i am still not satisfied.

I'll also add that 3200 is pretty much highway speed (70ish). I thought i had 3.08 gears but need to verify ( the math shows 3.73 to be closer, wife said we were doing between 65 and 70 tac was 3200-3500). Lock up th350 (lock up seems to be working fine)

Vette-kid

Thank you!