Posted by Paul on April 30, 2000 at 01:24:31:
In Reply to: manifold vacuum problems posted by m clark on April 29, 2000 at 00:09:42:
You need to find out why the vacuum is so low. It's way too low as it is. First thing to check is all the hoses that go to the carb. and other things such as vacuum wipers (I think yours are electric), brake booster, and the heater controls is they are vacuum operated.
If all the hoses look good or you have replaced them and it's still too low, get a spray bottle like you would use for glass cleaner and fill it with fresh tap water. With the engine running, spritz (<-----fancy technical term) the water around all the gasket mating surfaces. The main culrpit is usually the base plate gasket for the carb. but it can be the intake manifold also. When you're spritzing water, you will find the engine speed will increase as the water momentarily stops the leak. I don't like to use propane or carb. cleaner as it can be pulled in the air horns on top of the carb. and give you a false reading of vacuum increase.
Some other things it can be are a worn throttle plate bushing on the side of the carb., idle speed screw damaged or turned too far out, timing is too late, burnt valves, timing chain has slipped a tooth and several others.
I would bet money that it's just a bad gasket sealing. Can you put your hand over the air horn on the carb. and kill the engine? Does it whistle if you try it?