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Thread: testing for bent valves

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2010-11-29 18:58:38
testing for bent valves
I guess this can go anywhere but I have a vvl that after assembly with flat top pistons (installed reliefs) compression tested 245 245 240 245, and now is getting 200psi more or less on all pistons It doesnt smoke or anything! what are the checks I can do to figure out whats wrong
2010-11-29 19:07:15
You can pressurize each cylinder at a time when its on the compression stroke and listen for air coming from the intake, exhaust or from the crankcase breather. That will let you know where you have any leakdown.

Exhaust means exhaust valves are not sealing completely, Intake means intake valves, crankcase means rings are not sealing completely. You should only have very little leakdown and the only place it should be is by the rings.
2010-11-29 19:23:36
ashton could you expound a bit on how to pressurize the cylinder whilst on the compression stroke? ie. whats the actual procedure
2010-11-29 19:30:55
use your compression tester hose and put a fitting on an air hose from a compressor and pressurize the cylinder. They make specific hoses for this that are included in a leakdown tester. Ive also used an air gun with a rubber tip and long extension to go down in the spark plug tube, you just have to keep a lot of pressure down to keep it from leaking around the rubber tip.

Pressurize the cylinder with about 100psi of pressure. It can be on the compression stroke or bottom of the power stroke. Just as long as the valves are closed.
2010-11-29 20:28:20
I sent you link before with pics of flat top pistons in VE. Pistons have then "custom" valve reliefs and some valves were bent.
2010-11-30 16:07:35
Jagy, valve reliefs were installed... theyre a few thou deeper than stock vvl reliefs...
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