My leakdown results(please comment)...

[GregB7S4]

PPI on a 105k mile 1991 C2.

16%, 6%, 7%, 6%, 4%, 8%.

Should I be concerned about the 16%??

[Groesbeck Hurricane]

I'm sure better minds will chime in, but 16% is a tad high. Has the car just sat or is it driven? This could just be carbon build-up, IF I remember correctly. Will the owner go for a long spin and pay to have the test re-run? Is there smoke out the exhaust?

[GregB7S4]

No smoke from exhaust. The mechanic said the +16% cylinder was a little higher than he'd like to see but nothing to be too concerned about. He commented that it was leaking past the ring so I don't know if carbon could be the cause. I think I am going to buy it. Thanks

[AFJuvat]

Too high.

Optimally want less than 6% leakdown on all cylinders

[Groesbeck Hurricane]

I was wondering, how many miles is the car driven every year? Is this a garage queen? These cars like to be driven...

[GregB7S4]

The car has been a garage queen for the last 6 years or so, and if I buy it will continue to be driven infrequently..

AFJuvat-do you think these numbers mean an imminent top end job or can I put it off indefinitely? I will only be putting 2-3k miles per year on it.

[AFJuvat]

Rather hard to say if it would need a top end right away, or something else.

Pressure can escape through three places: Intake valves (air heard escaping into the intake) Exhaust valves (air escaping into the muffler) or through the rings (air escaping through the crankcase and into the oil tank or breather hose)

Your mechanic stated that the pressure was lost through the rings. If this car is truly a garage queen, it is possible that a ring lost its seat and will reseat itself after being driven for a bit.

If possible, have the owner drive the car every day for about a week and re-test

If not possible, I would pass on this car. FWIW most healthy 911s leak down less than 2%.

AFJ

[cupcar#12]

my thoughts,

my Cup just returned to the road afer a rather lengthy period - the engine was sitting on a palet in my garage for 3 years, removed jsut after the wreck.
te leak down #'s were similar to what you are describing and i have a "case half" leak as well after it had been run once. pretty disturbing stuff all in all.
2 weeks later and 200 miles - the leak is gone replaced by an oil return tube leak (easy to fix, and actually expected since everyting has to get back to running together) and leak down numbers before i left the shop of within 1% of each other (none over 2%)
YMMV but if it has been sitting then it could run out ounce you let it run a bit. Dive it and get it HOT once or twice and recheck ofter that. if you still have a +10% then worry

[aigel]

I would not buy it with those numbers. It may be nothing, but worst case it may be a new set of pistons and cylinders lurking there for you.

Unless you get the guy to drive the cobwebs out of it and retest resulting in lower numbers, those numbers would worry me. Why buy something that's flawed if there is plenty of cars out there with decent compression numbers?

George