Acceptable Leakdown Numbers for 82 911SC PPI???

[mercury26]

As the title indicates, I am looking for acceptable leakdown numbers (or percent variation) for an 82 911SC. I am getting a PPI done, so would like to understand if their are numbers that are unacceptable.

Cross posted on Rennlist.

Thanks,

Chuck

[Bob Kontak]

Hi Chuck,

Here is a link that folks talk about leak down numbers.

Also search using the advanced search option and you can find plenty more.

1980 SC - Compression and Leakdown

[gregwils]

There isn't much more to report than the info in Bob's link. Keep in mind that a compression and leak down won't reveal everything about the engine. You can still have high oil consumption. A leak down is done with the valves closed. They could be seated tightly in the head showing little air loss, but the valve guides and seals could bad causing high oil consumption.

A leak down should be done with a cold engine. If the seller will allow you to keep the car at the shop over night, then either you observe or the shop owner observe the size of the oil puff on start-up. There is a direct correlation between the size of the puff and the oil consumption.

[Peter Zimmermann]

Leak down test info; The Pre-Purchase Inspection by Peter Zimmermann - Rennlist Discussion Forums

Over many years I was familiar with, and maintained, a large number of 911s that would puff a bit of smoke on start up. Some of those cars only consumed one quart/3,000 miles, which is extraordinary. My car, with completely normal one quart/1,000 miles consumption, puffs a bit of smoke on cold start. This symptom is not an accurate gauge of consumption.

The most important thing about a leak down test is that it's performed correctly. Bad technique can produce bad numbers.

[mercury26]

Don Jackson Porsche in Phoenix is doing the PPI. I have heard good things about their shop, so we will see how it comes back.

Peter, thanks for chiming in. I am a fan of your book, it has been one of the "bibles" used in my 911 search.

Thanks,

Chuck