At 04:28 AM 3/10/01, Dan wrote:
>I have an engine without a timing belt - how would I perform a leak down test to find out if the valves are bent.  What equipment would I use?

It won't be very easy.

If it is a 32-valve engine, if the crank is not there already, carefully rotate the crank to the 45 deg position (marked on 32 valve engines, not usually marked on 16 valve engines). With the crank at 45 deg, you can rotate the cams without hitting a piston, even on an interference engine.

You need to turn the cams so that both valves are closed in the cylinder that you are checking. Trivial is you can see the cam lobes, tough otherwise.

If the crank is at 45 deg, it WILL turn when you pressurize the cylinder thru the spark plug hole. If it is in a 5-speed, 5th gear and blocked wheels MIGHT hold it. If it is an automatic, you will probably need the flywheel lock. I don't have a clue as to whether you could hold it with a socket and breaker bar on the crank bolt. Be careful!

The pressurizing fitting comes with a professional leak-down gauge set. If you don't have that, and just want to find (hear) where the air escapes, you can find one of the old "spark plug anti-fouler" fittings. Basically the bottom of a spark plug with threads in the top where you can screw in a real spark plug. Weld or screw in a piece of steel pipe, put a lever-type valve on the top, then an air hose fitting. Be sure that you can turn the fitting, pipe, valve and air hose fitting.

Carefully pressurize the cylinder. If the intake hisses, the intake valve leaks. If the exhaust hisses, the exhaust valve leaks. If the pressure cap hisses, the head gasket is blown, or the head is cracked. If the oil filler opening hisses a little, no real problem If it hisses a lot, the rings may be broken/worn. A squirt of engine oil in the spark plug might help seal the rings - if so, they are more likely to be worn than broken.

Wally Plumley
928 Specialists