I know, I know, you've heard enough about this, but really have you heard it this way?

When I drive with the windows down the heat is about 20-30 degrees warmer than if I drive with the window up - no A/C - heater off (Okay, well as off as it can be) - 80 degree day.

I took the car to the Woodward cruise this past weekend and of course ran into bumper to bumper. It got HOT! Then driving home on the freeway with windows down I had to roll them up for some reason and the cockpit got cooler all of the sudden.

Any suggestions? Threads? (I think I'm going to try the shutoff valve trick on the heater hose this winter so it's ready for next summer, unless someone thinks I can do it in a few minutes with the right equipment, and assuming I can find the heater hose. BTW I wasn't born with a wrench in my hand, if you didn't guess that already.)

Thanks again members,
Mark

mark, putting in the heater hose shutoff valves isn't hard at all. Just check out the link I posted, go to a plumbing store and get valves. Drain a little anitfreeze from the radiator, cut the hoses, put them in. Fill her back up and you are done. Start it and check for leaks. Shouldn't take long at all, amybe 1/2 hour- 1 hour.

You can buy the valves at autopartsgiant.com. They are made for that application. About 8 bucks apiece. It takes about two minutes to install them. Get both the 3/4 and 5/8.

James,
are you refering to part numbers 20500 and 20501? Do they require nipples put on them between the valve and the hose or do they fit directly into the hose?

Good question, James, I'd like to know the answer to that myself. An thanks for the part numbers.
Mark

Just cut the hose in a good spot and slide hoses on valve, then tighten up with hose clamps.

Oh, yes those are the part#

I had posted one reply on this earlier. I installed the manual shutoff vave. Purchased it from Autozone for I think 2 or 3 bucks. I installed it in the return line, only because I had a lot of slack hose. You can install it in either the hose coming out of the waterpump or the return. The whole point is to stop the circulation of water through the heater core. I have A/C on my 75 and by putting the shutoff valve in dropped the temp coming out of the air vents about 15 degrees. When I first had my A/C running, the temp at the ducts was 82 degrees. I found a lot of leaks in the A/C ducting, fixed that and installed the shutoff valve and the temp dropped to 68 degrees. I had a friend work on the A/C and he found that the expansion valve (new) was defective and was bypassing. He cleaned the original valve and reinstalled it and the the temp is now 48 degrees coming out of the vents. If you do or don't have A/C I would put a shutoff valve in. I have heard that not only the vettes of that era, but a lot of the chevys had problems with water circulating all the time.

I have a 76 L82 4 speed w factory air. Same problem - hot cockpit. Will do the heater valve mod. Thanks. That still doesn't address another concern I have, poor air circulation within the cockpit. Drive along at 70 MPH with the windows up on a 50 degree day and the vents open. Very little air circulates and that air is hot. Had a 68 with "astro ventilation". Great air circulation. In 75, Chevrolet removed the rear deck vents, behind the back window. It strikes me that those vents allowed air to escape the cockpit. same concept as opening one window in a hot room - nothing happens. Open the other window and now you have cross ventilation. Did the elimination of those back deck vents permanently close the other window? If it did, how did the engineers expect air to circulate within the cockpit? Need I consider cutting the deck and having those vents reinstalled? Please advise. Many thanks. Regards, JJH

I believe there is a whole vacuum system involved with those rear deck vents so it won't be a simple as cutting out some holes and running an air tube.