I have a 70 vert and on these hot days there is excessive heat on the interior even with the top down. Is it a common problem for a lot of heat going through the firewall in this year or do you think my heater is not completely closed?

 

I put a 5/8" ball valve with hose barb connections on my heater hose line to stop the flow of coolant to the heater core. (available at Home Depo or Lowe's for under 7 bucks) Many C3 owners do something similar. I still do get a LOT of heat through the firewall and floor. I used 1" thick fiberglass insulation with foil facing (duct wrap) under the carpeting and that does not seem to stop it. Some people are using Reflective insulation under the carpet (bubblewrap with foil facing) with supposedly decent results.

 

Lots of good stuff here:

http://home.comcast.net/~chadwick.ro...entilation.htm

 

Big Fish - The 5/8" ball valve sounds worth trying. I always thought you needed a continuous coolant flow through the heater core as if it was a continuious circuit. I'm going to install one tomorrow. Thanks.

 

I've checked the Chadwick site and it is an excellent restoration location. Hope I don't have to go that far. Thanks for letting me know about it.

 

A big culprit is the exhaust pipes that are routed down both sides of the transmission tunnel. Only about 6 inches of air, maybe 1/2 inch of fiberglass insulation (if it's still there) and a thin sheet of fiberglass seperate your right foot from the roaring hot exhaust pipe. On my 1968 Convertible my right foot used to get painfully hot even on cool days.

Check your factory insulation blankets under the transmission tunnel. Also, there's a insulation blanket "horse collar" that goes over the transmission to keep hot engine air out of the transmission tunnel. What about wrapping fiberglass tape over the exhaust pipes.....................or you can do what I did. Buy the factory option side pipes. This solved my heating problem completely. They connect to the existing factory manifolds or hedman hedders makes headers for this option. Molded fiberglass replica's of the original sidepipe covers are available that are cheaper that the $2500 cost (approx) of new original chrome covers. Hooker header type systems are also a cure for compartment heat. Hooker headers solved the heating problem on a 1969 Coupe that I owned.

 

Replacing the seal on the ventilation doors down by the kick panel is relatively easy and effective fix for unwanted cabin heat. This repair made a dramatic difference in the interior temp of my car, but my seals were both torn.

 

I retrofitted a later year C3 vacuum-controled water valve, inline with the heater core hose. Then added a second vacuum switch right next to the lower dash headlamp "up" vacuum switch.

Stopping hot water from flowing through the heater core sure makes a world of difference.

 

does the heater core then malfunction or rust without the constant flow of coolant through it? or can you just simply flip the ball valve and it starts working again?

 

Open the valve and your back to normal. My '82 has a valve that is closed when the AC is turned on, so I added a manual valve also so I can keep it closed. It has helped some but I need to work on the air coming in thru the vent in the kick panel. I figure I'll have it solved by the time it gets cold out, then I'll want it back!