Broken BB Valve Spring Part II

[Peter M.]

[William C.]

Re: Broken BB Valve Spring Part II

You need to have a constant source of air for the air pressureization to work in holding the valve closed. That is because the engine is not perfectly sealed, so additional air must constantly be supplied. Generally a 3-5 hp compressor with a good size tank will do the job. You need to get about 90-100 psi into the cylinder and Maintain it with the reserve from your tank and compressor to complete the job. You should be able to tell where the air is escaping once you have a constant air feed hooded up. If it is a bad valve, it will be heard leaking in the exhaust or the intake (thru the carb) and listening for the escaping air can tell you where the leak resides. Try another (undamaged) cylinder to get a feel for "normal", but adding air at all times in the process is normal.

[Clem Z.]

Re: Broken BB Valve Spring Part II

some times you get carbon under the valve seat causing a leak when using the air compressor so with air pressure in the cylinder before you remove the valve spring and retainer hit the top of the valve stem with a dead blow hammer so the air pressure will slam the valve back against the seat making a better seal.

[Peter M.]

Re: GM BB Valve Spring Unidirectional ?

Clem - I bought the purple GM valve springs with the correct heat-treated keys that you suggested. I noticed that the inner spring is coded yellow and appears to have two sides. One side is wound tight with three coils close together while the other end is equal spaced to a single flattened coil. Are both unidirectional with either side up or down?

[Clem Z.]

Re: GM BB Valve Spring Unidirectional ?

i never saw or heard what side was up but i always put the tight wound end of the inner spring against the head. JMHO