Belgian1979vette

I've made a couple of changes lately, under which a new manifold, fuel injection, a 195°F thermostat instead of the old 180°F and of course new coolant.

Now it seems like putting the ventilation on cold doesn't help. I keep getting hot air in the car.

Is this the heater shut off valve that is shot or something else I need to take a look at ?

terry82

can you tell us where the heat is coming from?if its coming from the vents then your shut off valve is not working.

Bikergems

It could also be your temp control. There is a vacuum valve behind the pocket which operates the water control valve. The temp control attaches to it. There is also an adjustment of this temp control built in on the cable. I have a 82 and had to replace the temp control cable and the water control valve.

Belgian1979vette

Yes it seems to be coming from the vents. Before it wasn't so hot.

thegazman

I have a 79 and I installed a manual shut valve in one of the lines going to the heater from the engine. It helped some. One of the problems with these cars is that no matter what you do your outside vent is going to pick up hot air off of the engine. It can be 80 degrees ambient temperature and your vents will be blowing out 90 degree air without the compressor running.

Belgian1979vette

I have rebuilt the seals on the flaps when I restored her, so normally they should seal up pretty well.

terry82

do the valve and see what you have .

cardo0

There is an entire seal kit for the heat/AC/ventilation box - try Doc Rebuild. There are many more seals than just the "flaps". The entire box is also sealed to the firewall with "monkey poopie". Have fun.

Also is your rubber shifter boot that is under the leather shifter boot torn or with holes? U would be surprised to find how much hot air gets into the people compartment from a torn shifter boot. And since it sits under the leather console boot its never seen/noticed. My trans tunnel got so hot i couldnt even touch it with my leg.

Why did u go to 195* t-stat?

Maybe u could let us know what works this time.
cardo0

thegazman

I put new seals on my 79 too, but when you have fresh air coming into your HVAC system it still draws some of the heat off of the engine.

CaseyJones

You added 15 degrees to the cabin temp by changing to the hotter thermostat. I'd change that back for sure. Then add a cut-off valve to the heater hoses. Either fix the factory one or use a good quality metal ball valve to the pressure side hose.

Belgian1979vette

I changed the shut off valve yesterday. Still have to drive her though.

I want to a 195° because I had been looking at different cooling temps vs wear and 195°F was the best compromise. I use a stewart stage III pump and that one doesn't have the coolant bypass. So my 180°F thermostat came with the 3 holes in them from Stewart, but it took forever to warm up especially in winter when it never even reached proper operating temp. So I had to do something to combat the problem. The solution was a line from the thermostat housing to the top of the pump and since I did that I also had to change thermostats. I was advised a 195°F was better for the motor.

Belgian1979vette

Well did a short run after she was warmed up. It got hot again but only when driving.

I checked the flaps. One side seems to completly seal off, but the other isn't.

I do use a L88 high rise hood and have cutouts in the rear reinforcement that gives opening to the windscreen. I did this to use it later as a intake for cold air for the engine.

Could this be it ?

If so what do I do about it.

PS : non ac car.

thegazman

If you come up with a solution to keep hot air from the engine from coming in the fresh air vents let me know.

terry82

if you have new seals on the flappers they should seal up very good.If not something is wrong.

Belgian1979vette

Yes, but the ventilation takes it's air from the cowl as well, so that's not really working well.

Belgian1979vette

I'm thinking of seperating the middle section where the hood overlap from the sides where the ventilation takes it's air.

I would not have expected it to do that, since the front of the windscreen normally is a high pressure area.

TheSkunkWorks

I'd close the hood's cowl back up until you install a proper CAI box to isolate the induction system from hot under-hood air. Also, be sure to install a correct rear hood seal. FWIW, the pressure differential at the base of the windshield is speed dependent, so you can still get hot air at lower speeds, but you probably already know that.

In addition to other items already mentioned, be sure to check to make sure you don't have a hole in the HVAC box near exhaust header at #8. Suggest either thermo wrapping that pipe for at least a foot or so, or to otherwise insulate the HVAC box. Mine actually disintegrated from exposure over time, venting very hot air into the cabin.

Belgian1979vette

This solved the heat issue today.



I extended basically the lower sides of the bulge in the hood in the rear.

It gets really close to the wipers, so this could become a problem.

Now, this is supposed to work as a cold air intake à la L88 but in view of the fact that it seems to work better as a heat extractor, I'm a bit questioning if a CAI would work in this location.

TheSkunkWorks

In addition to the factory having designed it to actually function, there have been many a string test proving that the L88 cowl induction really works once you get moving, including those that show air flow into rather than out of the hood at speed even without a proper CAI isolation box. Given the persistance of debates over this, I only wish I could post some actual pressure differential numbers as supporting evidence, but haven't had my shark running since before acquiring the proper instruments. Still, I think your extension might be worth further study.

Belgian1979vette

Well, the speeds she was seeing were around 70-80 km/h and I still had the heat issue at that point, so I seriously question the functionality of it all. However the Original L88 I believe was shorter and you had the ventilation door that could open, so it's in fact quite different. And then you still have the effect of a carb sucking in air.

Might be however that extending it like I did, moved the intake point of the hood's CAI closer to the windscreen making it effectively working...hm

If someone here has a good way to scoop cold air over those damn radiator frames with a suitable size hose and be able to hide a suitable air filter up in the front...i'm all ears.