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alwaysflat6s alwaysflat6s is offline
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Join Date: May 2001
Location: S.F. North Bay
Posts: 1,229
Hi Compression like a 2.8 RSR engine gets you up around 200psi. Not for street gas!

And I agree that using a leak down to better define a problem is valid and a LOT better thinking than just blindly doing a test. Tho, if you have low compression on 2 adjacent cylinders, you already KNOW you got a leak between the 2 [911/930 owners can ignore all this and should understand why I am saying this].

Remember, these devices were designed for pros to help them estimate how much and for exactly what.. they were gonna lighten customer's wallets. Prior to this it was a matter of holding a length of hose in the intake or exhaust, or inside the oil filler and listening for the hiss.. Not as trick, and you didn't get a nice percentage [to inform a breathless customer], but you KNEW what was going on.

It wasn't until the 90s that commoners started discussing this subject because almost no one did it and few people understood it. It was very handy for racers to determine how long before the big boom might be expected. Either way, if your engine is proper adjusted and you have significantly low compression on one or more cylinder... you got..a compression leak and that means something is old, broken, worn and gonna make you take your toy apart. Is it important to do a leak down to say.. OH it's a valve vs OH it's rings?

I hope you guys know I am having some fun with this..tho I am entirely serious at the same time. I say, if you don't have a leak down kit, don't waste your money. Someone with a functioning brain and a compression gauge is just as well off. My leak down kit is still lovey because it just..sits.. in it's nice box in the tool chest. Some day I will probably sell it to someone who wants to dazzle someone with facts.. or thinks he needs it!

Old 08-12-2010, 11:37 PM
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