I recently put an Edlebrock AVS2 on my 79 c3 and blocked off the egr and choke diaphragm. Is it possible this would cause the intake to overheat/retain heat? Thought a bad thermostat was the problem but it seems to be something else.

 

What do you mean by choke diaphragm?
The carburetor uses an electric choke so exactly what did you do, a picture might help.

 

From the Quadrajet that was on there before. Had to block off these for the edelbrock to fit. Egr was on the left of the picture, choke diaphragm on the right.

 

What temperature thermostat are you using?
Is the vacuum advance diaphragm on the distributor connected to a manifold vacuum source?
Does it run hot at idle or while moving or under all conditions?
Does it run without issues other than running hot?
What temperature does it hit?

 

hey thanks for taking time to help figure this out. A little back story, I got the vehicle in 2012 when my dad passed. And it’s sat other than a few repairs. I last drove it in 2012 when the ignition coil blew but I didn’t have time to diagnose and repair (vehicle was with family in Michigan, I lived in Alaska). Moved to Ohio last fall and moved the vette with me. Decided to replace the carb when the stay at home started.

the only thing other than replace the carb was painting the valve covers, and since I removed them I did change the oil. Also removed the heater hose. Seems to have circulation in the coolant since I’ve been able to burp it and see the air flow.

replaced the thermostat last week after It over heated and stalled a couple weeks ago. Got close to 220. I went with a 180° thermostat.

drove it last Saturday and it over heated again. After doing a neutral restart on the third stall, it ran fine about a mile home. It was up around 210° but cooled back down to 180° on the way.

burped it again and added some 50/50 coolant. First time driving it was last nights. Ran fine for about 20
mins, staying around 180°. Stalled out and ran about 200°. Took it home and parked it. Started reading up on possibilities other than just a dirty radiator. Saw something about the egr

doesn’t overheat while idling, however once warm it seems to stall and stay about 210-220°

I’ll have to check the vacuum assist, it’s hook from the distributor to the carburetor but I didn’t touch anything else on it

 

I put a 180° in it last week. seems to only over heated while running. Stalls out in the process. Doesn’t seem consistent but I am also not driving it and pushing the issue when it does.

Have to check the vacuum assist. I only removed it from the carb and hooked it up to the new one.

I haven’t ruled out the old dirty coolant yet. But trying to think of anything it could be.

 

On the right, that's where the heat stove goes. Before you get 800 more questions, can you confirm that your electric (?) choke is: 1. Electric, 2. Connected, and 3. Functioning properly (opening confirmed after warmup)?

Also, unrelated, what made you take your Q-Jet off the car?

If you are overheating, and you don't suspect a cooling issue (lots of threads on that), the #1 thing I would suspect is retarded ignition timing. What is your total mechanical (only) advance at 3000 RPM?

 

If that's the condition of the coolant and its the original rad, replace the rad with a nice aluminium one.

 

What is your vacuum advance connected to, make sure its the correct port,you may not be getting full advvance and it could be strangling the motor at speed.....Then I would check to see if your running lean either with the carb tune or the choke is staying on, then check timing, then look at your radiator seals. Overheating while driving is all air flow through the radiator and nothe fan, so if your seals are failing of missing the air will go around the rad and not throuugh it. Usually when you have an isssue its the last thing you touched. Blocking the heat stoves wouldnt do it.

 

Ill have to take a look at the vaccum advance later. Its hooked from the distributor into the carb matching the instructions from edelbrock.

 

Electric Choke, functioning properly. have to check the mechanical RPM. I am not sure right now.



Well that could be a bit of a history story on the vehicle. My dad bought it when I joined the Air Force in 98 and left it to me when he passed in 12. Since that time my Brother in law and friend (retired mechanic) had been doing the work. They had rebuilt the Q-Jet a couple years ago and recently suggested I replace it with the AVS. Trusting is judgement I went with it. probably could have made a couple different decisions and did some more research before doing it.

 

Last thing touched before the thermostat was the vacuum lines and carb, but the vehicle had sat for most of the winter, and really only been driven 100 miles since 2017.

 

How hot does it get idling? If it gets above 200 and keeps climbing maybe the thermostat isnt openning

 

Its fine idling, doenst get above 180

 

So you dont know if the overheating condition existed before changing the carburetor?
It also seems like you used an adapter to mount the Edelbrock which is not a good idea.
It would be wise of you to have the Quad rebuilt by Lars Grimsrud.
He can be reached at v8fastcars@msn.com

 

thanks. It was not overheating before the swap.

 

Do you have a vacuum controlled heat riser valve where the drivers side exhaust manifold connects to the exhaust pipe?
If so did you not correctly connect the vacuum lines and the valve is always closed forcing exhaust gas constantly through the intake manifold?

 

The edelbock is a square bore carb and you need the metal spacer adapter or you'll get a really bad vacuum leak at the spread bore rear of the manifold. But it requires gaskets above and below...it won't change anything performance wise

 

Somethings not right here. This doesn’t sound like purely an overheating issue. 210-220 degrees is warm, but it’s hardly overheating and certainly not enough to cause the engine to quit. Not sure what but something else is going on here.
I’m thinking I would start with the basics: compression test, leak down, timing. Then go from there. If I had to hazard a guess I’m thinking head gasket??

 

I just reread that, over heating is 240/260 plus and blowing steam everywhere. IF it just gets to 210/220 then stalls its a heat related issue. It sounds like it wold be an delectrical or fuel related issue. Maybe you have a bad coil, a cracked cap, youre vapor locking, or have a fuel pump issue.

Edelbrocks are known for being heat sensitive and needing low fuel pressure, but it doesnt account for the temperature increase. If you have the quadrajet, thow it back on and see if the temp isssue goes away. The stalling may just be a symptom of the overheating, or the stalling is a symptom of something else and the overheating is also a symptom of that other problem. So elimate possible causes. Start with the carb and then check your tune up. if changing that doesnt do it you may have to get your radiator flushed. Maybe its flowing enough to stay cool at idle rpm ,but not at 3000 rpm. If there is alot of mud in your system you may have to flush it 3 times, i had to in my old motor.