Installed the foam insulation piece in the mouth of the tunnel to stop air flow from engine compartment into tunnel. What a difference that make cutting the flow of hot air into the cabin. If yours is missing replace it will really cut down the heat level in the cabin. Really cuts down on the bitching from the right hand seat.

 

Can you help me with some install advice? I have a 78 l48 auto. Type adhesive? Glue to the tunnel or transmission? Any other advice? Thanks

 

I still think those "collars" are a bad idea. Blocking engine bay airflow just seems wrong to me and may result in additional engine bay temps.
Its been known for decades that it is difficult to get any air circulation around and through a C3 engine compartment.
To block off one of the major hot air exits, in my opinion, is not the solution.
But, its your car.

 

Thank you for the info. My cabin is also hot. Can you elaborate a bit where the foam goes?

 

Used Gorilla Glue and glued it to the tranny and the fire wall flush with the fire wall. Cleaned both surfaces with grease remover before glueing. Stopped the flow of very hot air up thru the shifter boot. Air conditioner now keeps cabin very cool and comfortable and not necessary on cooler days. Don't have to run it as much with the t-tops off.

 

Also,,,,,, If you divert the air down instead of straight back from the engine, this changes the total airflow under the hood, down and out,,, which is a good thing. One more project.

 

I thought that too but it has made no difference in engine temp, runs very cool with or without a/c and at any speed. Thought it might make a difference in traffic and so far have not noticed any issues. I get good air flow out the fender vents. I have had an aluminum radiator for some time and have the full shroud and seals. My idle speed is set at 800. I have never taken a temp under the hood but it is hot. My shifter boot allows air to flow out aruond the shift lever and that used to get the lever and **** very hot on a long drive, no more since the foam was added.

 

On top of the transmission flush with the fire wall to fill the gap between the fire wall and the transmission bell housing. Bought the piece from Ecklers, 20-30 dollars which I thought was a lot for a piece of foam. Made a pattern before I put it in because the heat is going to deteriorate it and I now could make another one. I read somewhere most C-3s are missing the piece. I'll try to post a picture of the piece installed.

 

Last time mine tore I just bought some of that high temp pipe roundish insulation material at the local hardware store and it's been working great for years. Something like 2 bucks (or less).
I do NOT glue it in. It's crammed in there and it isn't going anywhere.

 

originally glued but it will fit in there by hand and tension will keep it in.
the hair dryer through my e brake handle was greatly reduced

 

the assembly manual recommended glue so I glued, hair dryer was putting it mildly mine was closer to a blow torch

 

they glued it because it needed to stand up while body met frame on assembly. someone once posted a picture of it somewhere..it will hold fine without

 

 

Been saying this for years.

 

I used a rubber pipe insulator not the foam ones, about 2 inches around. It only took about 20 min to stuff into the gap.

 

If I can ever get back around to my C3, I'm gonna' try a stick of that hardware store pipe insulation as referenced above... anything to help block some of that heat
coming through the tunnel has to be an improvement.

Also as mentioned... the steering column is another significant source of heat in my car. Maybe some kinda' shielding between the manifold and steering box?
Not sure but would like to hear your thoughts.

It's no wonder the A/C systems have to work overtime just to keep things tolerable in there.

mardyn

 

I thought of that as well. The steering column is thermally insulated from the steering box by the rag joint. So it is only the upper exposed part of the shaft to worry about. And yes it is very close to the exhaust manifold. So radiant heat from the manifolds would be high. I believe the flat mounting bracket which has a very high surface area compared to the shaft would be the big heat collector. What do you think about a ceramic black coating on those two parts to reject some heat?

 

I really am shocked when I hear about these heat problems. My 77 has

- factory foam collar on transmission (glue is not required.....I stuffed it in,...it never moves)
- factory rubber seal around back of hood to keep engine heat from spilling over into wiper bay (which is where the air comes from that flows into the cabin)
- when I rebuilt the car six plus years ago / 18,000 plus miles ago, I resealed the heat doors and the A pillar vent doors, i.e. the seals actually seal compared to 40 year old rotted seals)
- Lizardskin heat sprayed on inside floor and firewall of car
- factory firewall insulation
- Lowes Reflectix under the jute backed carpet.
- any holes in the firewall are plugged with either wires, hoses, or caps.
- in 77 Chevy had did away with any under floor metal of plastic heat shields.....so got none of that either.
- fully functioning heater system in the car, with the factory vacuum shutoff, which supposedly fails all the time....but mine works. I have ZERO heat flowing out of the floor heat ducts with the levers in the OFF position.
- I have NO freon airconditioning..factory heat / defrost only.

My 406 SBC has StainlessWorks UNCOATED 1-3/4 inch headers to 3" collector to 2-1/2 stainless under car exhaust. That collector on the driver side is less than THREE inches from my right foot on the gas pedal....and I feel ZERO heat on my right foot. With all of the above......I feel ZERO Heat flowing inside the car, and by no means is it "unbearable" as some have proclaimed. With the exception of the Lizardskin and Reflectix, my car is as Chevy built it. NO HEAT ISSUES AT ALL, with UNCOATED stainless headers.

Now....my engine compartment is wide open, because I do NOT have Airconditioning pumps and housings, I do not have any EPA garbage, no power steering pump, and no Brake booster. There is alot of airspace around the engine. I have my Dewitts aluminum radiator fully sealed around the perimater, with a factory five blade engine driven clutch fan and factory fan shroud. I have no way to prove this, but I believe that a lot of air flows into the engine the engine compartment, down and out the side fender vents,.....because its wide open. You compare my compartment to an 81........the 81 is topped of full of garbage, wiring, ductwork, hoses, etc. All that garbage is a restriction to airflow, essentially containing the heat rather than venting it. FYI - my engine runs solid 180 degrees all day long, no matter how hot outside.
But whatever reason........with all the above, I have no intrusive or obvious heat into the car through the body or out of the heater system. I actually fully implemented the factory heat system last winter (all previously capped off).....just so I COULD get some heat into the car for early spring / late fall driving in PA. One last caveat........I drive the car 90% of the time with the T-tops off and windows down. When it is 90 degrees outside in PA......its 90 degrees hot. But point is,.....the engine heat is NOT adding to that at all. ZERO.

So.....whatever you all are having problems with.....maybe read my entire post and see what you are missing. And.....my steering column, nor my factory 4-speed shifter get hot, ....or even warm....ever.....even after hours of driving.

So.....I just don't get it??

 

agreed adding the collar cured my heat issue I may open up the heater core again.

 

How do you know that?