SLVRSHRK

I am just finishing up my interior and sealing the HVAC system. Finally got the heater hoses installed and started it up to test the system.

All of the vacuum stuff works great and the flow is awesome! Wow, I wouldn't believe sealing the vents would make such a huge difference in the amount of air coming out of the vents. These things leak like siphs when the foam rots out.

Anyway, I was installing my heater hoses and found another good place for people to check to see if they are getting hot air from the engine compartment into the system. There is a foam seal that goes around the heater core inlet and outlet that seals the case. It was gone on my car when I disassembled it. If it is missing, it allows hot air from right above the exhaust to enter the system.

Just another of many possibilities.

carbster09

Good luck guys! I double dynomated my internal. It made a difference, but I think its not the whole answer. I need to check better for leaks etc.

Now my engine is running hot after installing a high flow water pump and thermostat from Stewart. There's no end to the cooling problems for BB cars, driving them in Texas just isn't fun in the summer. I almost want to get rid of the old girl. Yes I am getting frustrated!

I noticed that there is no collar or shield on top of my transmission. I believe this might be a good source to insulate. Also has anyone tried teh exhaust manifold "blankets" from thermo-tec? Its a whole cover that is wired over the manifold. I don't want to remove them as they are a b*tch to get at with A/C and the little room afforded by a BBC in a vette.

carbster

71SoCal

I had my heater core out a few months ago...I didn't find any type of foam seal anywhere! I didn't even know one existed...that's got to be a major contributor to the heat. Time to pull the heater core out again and start ordering parts.

Thanks for the info...

Taijutsu

When my mech pulled the dash, he found 5-6 holes 2" or bigger. That can't help. Haven't driven the car for months, in the shop. Can't wait to try it in the heat. Lake Tahoe should be a good shakedown run.

Rick

rihwoods

I think it important to identify the heat source.That is why I bought an IR gun....I know where,how much,and will know the result afterwards...But leaks thru firewall,vents, must be resolved first,IMO....

Vette Dent

I found this thread after nearly melting my sneakers the other day in my 68 vert - Thanks for some good info.
Today I put a ball valve on the top heater hose. What a difference!! Also slapped a couple of pieces of duct tape on the speedo cable hole and one on the tach cable hole. This made such an unbelievable difference.
Then I went online and ordered the bell housing collar and the exterior floor insulation panels.

SLVRSHRK

You shouldn't need to pull anything to install the heater core seal I am referring to. Disconnect the heater hoses from the core, the new seal (about 1" thick foam) will slip over the hose stubs and then you press it up from underneath the car to seal.

If you want to reseal the whole thing, I would recommend Dr. Rebuild for the seal kit. It was very comprehensive and fit as advertised.

Good luck

CMYC4GO

My 76 used to get like a brick oven inside. The OEM heatshielding was crap. I ordered some space age stuff from JC Whitney, pulled up all the carpet, and went to work. Covered everything that was coverable with this stuff, and it was a difference of night and day. I forget what it's called, but supposedly it's used by NASA. It came in a big roll (enough to do 3 Corvettes) and if I remember right, it was about $80 for the roll.

vettfixr

This thread keeps popping up so I'll add my $.02. My car was almost undrivable in any temp over 75-80 degrees. I went through all the usual suspects until I stumbled upon the fix for the air plenum that's built into the right side fender. Look at the Tech Tips section for that fix and I'm sure it will cure 90% of the problems stated here. In addition to that you have to have a shutoff valve for the heater core that you can get at any hardware store for under $10. You should also make sure all the seals in the heater box are functioning properly and that the heater box is sealed correctly to the firewall on both sides. Dr. Rebuild sells a kit for this. You can insulate the cockpit using many different materials. For details on this go to my website and look at the article on insulating the cockpit. With all of this done my 74 is no hotter than my '05 350Z roadster.

CoolShark

Do you have to pull the tranny to put it in? I need to replace mine on my 72 4sp and it looks like a real pain.

Hef

I went to Summit and found the product you mentioned.
http://store.summitracing.com/
Heat Barrier, Super Insulator Mat, 48 in. x 72 in., Universal, Each
Monday $27.95
In your pictures on your website http://mywebpages.comcast.net/vettfixr/page14.htm you have the insulation on the inside of the cockpit, others have mentioned on this thread to place the insulation on the outside, to keep the heat out. Any ideas on this?
I looked under my 79, and looking at the bottom of the car, where I think the feet rest is, it doesnt look like there is any shield - just a flat fiberglass plate. Should this be shielded on the outside>

jbs75

The best place to insulate is outside the passenger compartment before it has a chance to get in.

rihwoods

The early C3's (73 ??) had a metal shield attached to the exterior footwells...I have some pics...but with todays materials/adhesives,you can easily do it that way with just insulation....I'm getting ready to do mine..

Pic of "early shield...

lostpatrolman

I believe it was 68 and 69 that had those shields.

WhichVette?

My 73 has those.

l979 Corvette

I have the same heat problem. I believe it's my heater core. The heater just doesn't turn off. Does any one think that replacing the heater core would fix the problem?

71SoCal

Yes, my '71 has those shields as well. Obviously the engineers knew about the heat problem as well.

I doubt that it's your heater core that's bad, it doesn't sound like it's having any trouble making heat! It sounds like you might need a water shutoff valve so the hot coolant won't flow into the core. There are some posts already in this thread that talk about that one, and some good articles in the tech section as well.

ESU

I doubt it's your heater core also, just add the ball valve on the upper hose to the core and keep it shut. You should notice a little diffrence.
I also just ordered the thermo tec self adhesive insulation from summit, I'll try it on my 79 where the earlier cars have that shielding and see if it helps. Hope it sticks to the underside of the car OK.
ESU in NY.

scotty13

has anybody put that refletix type stuff (fiberglass backed with foil) on the outside of their ac/ heater box?

rihwoods

Not me..but I'm installing it this week on the exterior footwells first...also going to seal that vent plenum(inside) on the pass side kick panel...I'm not getting high heat through ducts..My heater is disabled...