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Old 03-02-2005, 11:00 AM
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Checking cylinder pressure?

Hey guys I just finished the top end of my 454. All the valves are adjusted for the solid lift cam and I have cylinder pressure on all 8 cylinders. (Finger over the spark plug hole method). Is there away to do either a pressure check, leak down check or some other test that will show either good or bad cylinder pressure? I just figured that this could be an easy step to do as an FYI. Everything in the motor is new and I have no worries about it. I just thought I would do it to learn something new. If there is a way what would I need and how would I do it.

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Wade

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Old 03-02-2005, 11:08 AM
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Get a compression tester at your local parts store. It screws in place of your spark plug. You then hold the throttle open and crank the engine over a few times (disconnect the ignition so it doesn't start) and you'll get a PSI reading. Do it to all cylinders and compare their readings. You want them to all be similar (+ or - 10). Has the bottom end been broken in yet? If not then your readings might be a bit low until your rings have set.
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Old 03-02-2005, 11:15 AM
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Oops sorry I forgot one important peice. The engine is still on the stand. Can it still be checked by manually turning the motor?

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Wade
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Old 03-02-2005, 11:15 AM
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cylinder psi

If that engine in a flat tappet cam i would not do a cranking compression test until you have the cam broke in and the engine run for a few miles..... Cranking an engine with a new cam is almost instant death if it is a more agressive solid!!!!!!

You can do a leak down on it if you are concerned... I am not really sure what it is your looking for?????

Keith
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Performance engines
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Old 03-02-2005, 11:47 AM
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Not really looking for anything in particular just curious if you can do it while it is on the engine stand. Like I said it was just extra information gathering.

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Wade
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Old 03-02-2005, 11:56 AM
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Ok

Yes you can do the leak down on the engine stand. Make sure the cylinder is about 5 degrees before TDC and that both rockers are closed. Remove any tool you might have on the crank for turning the engine before you apply the air!!!! If the engine spins and the rachet wacks you in the knee or some other precious area of your body it will bring tears to your eyes!!!!!!

If it's a all new engine and the rings were not seated you might see leak in the 8 percent range... if it was a low milage engine that was in good running shape and you did the top end only it might be as low as 4 percent.....

Keith
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Old 03-02-2005, 12:00 PM
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Thanks Keith.

It is an all new engine fro top to bottom. It is the first one I have put together in about 17 years or since I was 16. What tools do I need ? I am assuming it is some type of guage that will screw into the spark plug hole and have a separate connection for a air line? Preasurize the cylinder and watch the guage?

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Wade
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Old 03-02-2005, 01:27 PM
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tool

Yea you can do a search on the net.... There are some sites that show you how to build you own tool. I have a MAC with dual gauges. You screw it into the plug hole and run it up to 100 psi. Then you read the other guage for leak... If it would read say 90 then you have 10 percent leakdown...

If you get a cylinder that has a bit more leak then the others you can sometimes take a plastic hammer and tap the valves and they will set better and bring the reading back.....

Remember this is only a tool. The readings are not the end all... If you come up with 30 percent leak then there is a problem. But 10 percent would not be a problem in a engine that has not been broken in...

Keith
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Old 03-02-2005, 01:37 PM
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Gr8 info Keith thanks!

Wade
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