90% leakdown in one cylinder?

[Rich76_911s]

I just ran a leakdown test on my engine and got these readings:

Cylinder % Leakdown
1 7
2 3
3 11
4 95
5 15
6 10

Why would one cylinder be so terrible when the rest appear to be well within reason. This is a swapped engine so I do not know the exact history behind the engine. We retested the cylinder to see if we did the test incorrectly and came up with the same results. We even turned the engine over with the test running. We could hear the exhaust valve open and close but did not hear any signs of the intake valve doing anything. I was listening near the air filter, that is not in place, and heard no signs of air from there. Any help, opinions, and all prayers would be greatly appreciated.

[john walker's workshop]

well, you can certainly burn just one valve, score just one piston, bend one valve, etc. there is valve clearance, right? another common problem is a wallowed out seat from the valve beating around on it because of a very worn guide. that's actually the problem with most 911s that need a "valve grind".

[Rot 911]

I had a similar situation and it turned out to be one burned exhaust valve. However all the valve guides were worn.

[vichang4]

Could carbon stuck in one of the valves cause this big of a problem??

[Grady Clay]

Anything is possible.

I think Kurt V's experience should be a lesson for all.





That is as close to total disaster as anyone can come.


Best,
Grady