I have 1 '72 El Camino that has a small plastic valve on the engine side of the firewall in the middle of a vacuum hose that goes from the engine through the firewall to the heat A/C system. I assume it supplies vacuum to operate the various heat and A/C vents, doors, etc. The GM part number is 1485553, although no one has one as its probably an outdated part. My question is, can you simply eliminate the valve and just run the hose direct, without the valve? Any help or ideas would be appreciated. Thanks!

It's probably a delay valve to slow down the change in vacuum to the controls. Without it, doors may change position slightly when engine vacuum changes rapidly.

Actually, I believe what you have is a vacuum check valve. It will not allow vacuum to be pulled back into the engine on acceleration, which would cause your heater or defroster to shut off. This is a pretty common valve you can pull off most any vehicle as long as it's the same size as the one you have.

Thank you. I thought it might be a check valve of some sort. I'll try find one on my next visit to the salvage yard.

They also sell those in the "Help" section (Dorman/Motormite) at your local auto parts store...