An other question for my 1989 Chevy Caprice Wagon: The engine is a 307 (The Oldsmobile) and with carburetor 4 barrels and my question is: can I replace the actual whole air filter and put a simple round air filter? Can that will affect the whole balance? I try to check why the engine run beautifully cold, and when hot it loose power, hesitate, and knock. I have to go with the lower transmission gear (2) to regain some power. Any thought will be fantastic. Thanks.
There are several vacuum switches used during warm-up and to control emissions. One controls the vacuum operated flap in the air cleaner horn. When the engine is cold, it is shut and the carb draws warm air from the tube that goes to the exhaust manifold. Once up to temperature, it opens and allows fresh air thru the horn. If it never opens you will always draw hot air from the exhaust manifold. if that's the case, either replace the switch or block the flap open. Another switch controls timing advance to the distributor during warm-up. It might also be part of your problem. Lastly, check how much slop you have in your timing chain. If there's a lot, it could affect the problem you're having.
OldFox, it works. I get rid of the flap and plug the hole where the hose arrive on the horn. Now it run only on fresh air. It is perfect. Many thanks.
