Hello all, I am new to the forums but hope to hang around and learn a lot from all the knowledge around.

Currently I am looking about buying an 82 Corvette Coupe from a local guy that had the blown 350 replaced with a new 383 Stroker. He said since he took it back home from the shop that did the work it has been overheating when driving it on the highway for about 15 miles or so. Said he has replaced the thermostat already. Without actually working on the car I am guessing maybe the radiator is too small so a new hi-flow one would be needed. Also maybe the clutch fan is going bad so replacing that with an electric or new manual fan. I was hoping i could get some input from those with the C3's already.

 

I currently have a 79 with a high performance 383, i went to extreme measures to eliminate heat in mine ( long alu. water pump, stainless hoses, dual spals pulling and 2 10s pushing, with an alu. radiator) i also put an oil and tranny coolers. imo what all you'll need to cool it depends on whats in the motor, the stock system was only designed to cool a stock 350, not a performace 383. if its a mild 383 a short high flow alu. water pump and an alu. radiator would make a huge difference, if you dont feel like spending that money right off alway check to make sure all systems are operating properly and leak free, water pump, fan clutch, and radiator. again the more radical the motor the more you will have to look into more efficent cooling.

 

It might not have a problem. He should first test with an IR thermometer under the upper hose or T stat housing to ascertain the actual temperature instead of shooting in the blind.

 

I would check som visuals first
Are all the radiator seals in place?
Is the fan shroud in place
Is the fan clucth working
Is the chin spoiler in place on the lower valance?
Are the rad hoses in good shape? See if the lower hose is collapsing it has a metal spiing inside it may have rusted away.
The IR gun is a good suggestion to see where you are really at
measure the temp at the upper hose and the lower hose see what temp drop you have
Some of these items maybe missing or broken.

I run dual flexolite fans with an aluminum rad And a high volume aluminum water pump in my 383 never over heats

 

In addition, just make sure the stock cooling components are okay. If you're just cruising down the highway, the new engine shouldn't make any difference. It's only 9% bigger displacement, and the road horsepower difference should be insignificant. A few guys have had problems with the lower hose collapsing, drastically reducing the coolant flow. Just take a calm look at all the individual components, and see if there are any problems with any of them. If you strike out finding the source of the problem, just post your findings, and we'll go from there.

 

wow, way more ideas and suggestions that I had hoped for. I appreciate all of the answers. I will see if I can go over there tonight and look at the car.

 

Does the car cool down when he slows down? If its hot on the highway, but cool around town that's usually a coolent flow issue. Plugged up radiator, thermostat not openning all the way, or someother restriction.
Once had a customers car that was doing this after he put in a new engine. Turned out there was a chunk of casting sand in the new intake. Took a while to find that one

 

another thing to think about is the coolant sensor itself.
i know there is a big problem with aftermarket senders reading too high with our wiring systems.

 

OK, so I went and looked at the car. I was wrong it is an 1980 with the original 350 motor but rebuilt with a 383 Stroker kit, the motor only has 270 miles on it since being rebuilt. He replaced the thermostat while I was there and we took it for a little spin. Seemed to be doing great even with the temperature so he asked me if I wanted to take it for a few days. So I drove it home, but on the way home there was a loud pop almost like a back fire and the car died. I was only going about 60 mph and the temperature was not hotter than the normal but not too bad, still have a bit to get to the 3.4 line before the RED. I pulled over on the highway and tried to start it and it would idle for a minute really terribly then die off. I was able to get it started and moving enough to move it further off of the highway. I called him and he came to me. When he got there we tried to start it and it wouldnt even idle any more like it had for me a few times. He had AAA come get it and take it to a shop he deals with a lot. So hopefully they will figure out what is wrong and he is having them take a look at the over heating issue too, as well as the blower not working anymore on the vent/heater.

I will post here when we get it back and figure out what was wrong with the overheating to begin with.

Oh one more thing I wanted to ask. There is a little switch to the left of the ac/heater controls that moves up to on and a little light then down to off.. What is this switch? I have seen it on a few more C3's in pictures.

 

The popS you heard sound to me like fuel and or ignition issues. Both of which can cause overheating

 

Interesting.. can you go into more detail about how either of those would cause the over heating?

I noticed that on the stock vettes the air intake is connected to the front and some sort of air scoop, at least in pictures. On this vette there is an Edelbrock round intake on top. Would this cause any issues?

 

That little switch is for the rear defroster on my 78. I assume it is the same for the 80.

 

Ok so I am about to go pickup the vette from the shop the guy took it to. Turns up it was the coil that burnt out. Not sure why that would happen. Guys at shop also told him that the reason for over heat is fan shroud is missing. Which I noticed but thought there was a reason. He is going to try and find it this weekend. Hopefully that will get it good and then i can pick it up off of him.

Also TY for FYI on the little switch and all the other help!!

 

Check your timing. If it is at 6 which I believe was the factory spec for the 350, that's not enough for the stroker. Take it up to 12 and see what happens.

When I take mine down for the smog test,it runs hot.

 

I will check that tomorrow, forgive me if I ask a stupid question but this is done by rotating the distributor correct? I have never had a performance vehicle nor had to mess with timing. My wrenching mainly consists of things related to my old Jeep wrangler that I upgraded the crap out of, lift, new axle, new xfer case, replaced head and gaskets after sinking it in the river, stuff like that.. :-)

I did notice tonight when I was driving that it only heated up over the middle when on the highway driving 60 or plus. For example it was fine driving around my house, but I hopped on the highway and headed to my friends 30 min away it headed up. When I got off the highway and took the back roads up to the house it cooled off to the middle.

 

I just finished rebuilding my 350 to a 383 with over 400HP. My radiator is new, and I added a DeWitt's dual fan kit to eliminate the clutch fan and shroud pita of removing and installing. Haven't been over 195 yet...and it's been HOT out! Even ran about 50 miles running the AC.
I agree with the above, check the actual temperature first so you have a starting point. Get rid of that clutch fan if you can, make sure your radiator is clean and your t-stat is working. Just adding a big radiator may not fix the problem. You've got to find the problem first and deal with it. It's not rocket science, but it's close.
Timing is very important! When we were tuning my 383, just being off a few degrees in the timing was the difference between red hot collectors and running much cooler like it should. Mine was happy around 10 degrees.

 

So on the timing, if the stock 350 has been rebuilt with a 388 Stroker kit wouldn't that change the timing that is written on the block? I have never dealt with timing but I know it has to do with something on the block, and then using a gun to see how fast the main belt is moving and I think adjusting the distributor cap..

 

i just dropped in my stroker a month or so ago.. i went with a new late model block instead of using my old one. afr heads, 9.6 : 1, 450hp, dewitts rad w fans. never gets over 180

 

There should be a decal under the hood that shows the timing for a 350 in a 1980 should be at 6 degrees before top center. With the 383, try it at 10 to 12 degrees and see how it runs and if it runs cooler.

You will need a timing light. One of the wires on the light has a clip on it that you attach to the #1 spark plug wire (left front plug viewed from driver's seat).The other wires go to a + source such as the alternator, and to a ground.

Remove the vaccuum hose from your distributor and plug it with something like a golf tee,

There is a silver tab on the front of the engine. When you shine the light on it a white mark will show up on the tab to show the timing. If it is at 6 and you want to increase the timing to 10, loosen the bolt on your distributor and turn it to the left (clockwise) a little bit until you are at 10.

This will also change your idle speed,so you will have to adjust the screw near the carb.

This is pretty simple, but seems pretty forboding the first time. You might want to have someone demonstrate the process.

 

Thank you for the explanation. I will see if I can find someone local to show me how, and pickup a timing light for my garage.

I did notice that it is idling a little to high after you have driven it a bit so I was going to check that out this weekend too.