jazzz007

Doing a little make over on my 2000 SS. I am doing a leak down. How long should it take for 100 psi dry air to leak out of a cylinder? please help! When I brought it down I thought I had scorched some valves and they were a little pitted. Just added heads, 232-238 , 114 cam, new tranny with all the goodies, 3600 stall, long tubes and 4.10s. I sure would hate to tear it back down. By the way I do all my own work so labor is at least free.

derek_silvy

This does not help you... and I hate to get off topic, but how do you go about a cylinder leakdown test?

jazzz007

Take a compression gauge and add a connection for air pressure. Pressurise the cylinder , valve out the air and wait. My problem is I'm loosing pressure into the crank case. I just need to know how much is acceptable. It really hurts because of all the new work.

derek_silvy

That sucks man. So you just bring to TDC (to close valves, and see how much gets blown by? Some leakdown is completely normal right?

Cstick

Well first off, you should try doing a leak down test the RIGHT WAY. Go buy/borrow a cylinder leak down tester!! With the correct tool you will only supply about 35-40 pounds of air into the cylinder. Up to 60% leakage is acceptable. Less than 40% is good. 100 pounds of air is most deffinately going to leak somewhere fairly quick, even in a good engine (rings would be the easiest place to leak). I do not see how your method of using a compression guage tells you much of anything. You need the right tool.

Cstick

Secondly, the 35-40 PSI with the correct tool is constant. You are wasting your time if you are using a stop watch to wait and see how long it takes to leak down to a certain #.

jazzz007

Found the solution to the problem. Took my setup to a buddys 99 SS. Knew his blow by was minimal because of a rebuild and compression test. Hooked him up and it took his 13 seconds to drop to zero. Mine took 15 seconds so I know I'm OK . thanx God ! By the way CSTICK is absolutly right. It would have been much easier with the proper tools but I didn't have the right tools and my current expenditures have left my reserves at an all time loooow. got to save enough for a dyno tune and a trip to the track. Thanx for the imput.

JS

iTrader: (4)

I just filled the cyl. to 90psi and turned the engine until both valves were closed.Theres a fine line between open/closed but after doing it u kinda know where your at when u hit tdc or just before it.

I had less than 3% in every hole both hot and cold.The only thing I wish I wouldve done is go forged pistons.The stockers rock (Hypers) until there warm but ring seal is awesome in my motor.

ROCNDAV

iTrader: (100)

I'm not sure about this particular tool but Autozone & Pepboys often loan out tools free of charge. You need to either leave your Credit card info or Driver's license (if just going outside for a quick test).

David