Black911RS

I had this question on another board and after reading here, there seems to a good amount of perspective. So here goes: Deliberating a mid 70s 911 3.2 transplant:compression 1/150, 2/175, 3/175 4/166 5/170 6/170 with a leak down result of 35% on cylinder 1 No rust. No leaks. Given the caveat that numerous variables can affect compression, should these numbers cause concern? The leak down can (I'm told) be corrected with valve adjustment and valve cover gaskets
I am on the cusp, 911 gravity is pulling me in, I don't think I can be stopped... Is there logic that can stop me?

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Steve Weiner-Rennsport Systems

Hi,

That 35% on #1 is a problem. The technician doing the test should have told you WHERE the leakage is coming from: intake, exhaust, or oil tank, as thats the real value of a leakdown over a compression test.

Ed Hughes

What Steve said, and the logic you need that if it is something serious, it is serious money to repair. If it's valve, it could be $5-8K, if you have someone do a topend. If it's rings, you're WELL north of $10K, easily 15K+ to do a full rebuild, right.

Now, here is the real advice: Whoever told you valve cover gaskets can effect compression leakdown, and that new ones can fix this problem, is truly clueless, and is one person to run away from. Where did you find such advice?

As to the same person saying a valve adjustment will fix the issue.....well if the same idiot did the last valve adjust and had no clue on what they were doing and screwed the elephant foot down enough to keep the valve open.....well, they're simply lucky that they called their mistake.

Ed Hughes

Sorry to be harsh. You are seeking input, and I surely gave it. But, whoever is advising you is one you need to ignore. If it is the person doing the leakdown, maybe you need to try someone else.

theiceman

I can see what the mechanic is trying to tell you and you have to assume some "signal loss" between mechanic to you to us.

I would say he is telling you 'best case" is that there is a valve too tight and slightly open . if this was the case a valve adjutment would be required and he would also charge you for a new set of VC gaskets to put on as that would be required after the valve adjust.

if the test has been repeated i am assuming ( and its a big one ) that he has determined where the source of the leak is coming from ( either intake or exhaust ) .

The part i dont know and i will let ed and Steve comment is that there have been issues with valve guides on Carreras . I just dont know enough to know that if they were worn could they cause leak down issues.

If so you are definitely looking at Eds dollar numbers if you cant do it yourself.