1986 911 Carrera 3.2 leakdown and compression numbers

[ianleach]

What numbers should I be looking for to determine a healthy engine during a PPI?
Thanks in advance.

[Jcslocum]

Exact compression pressures are hard to predict. Even pressures within a small range is what you look for. A proper test is done hot, throttle locked wide open, battery charger on and cranked until no more pressure increase.

Leakdown should be less than 10% at most. 5% would be real nice. Anything over 10% they should be listening to the intake, exhaust or oil fill to see if they can hear the air leakage.

These are just guideline and my .002

Good luck!

[larrym]

Wayne sez:

A newly rebuilt engine should have leak-down percentages of around 3-5%. An engine in good running condition should show 10% or less. Numbers around 20% indicate some wear of the engine, but are still adequate for good engine operation. Leakage numbers of around 30% indicate that there are problems brewing,
Pelican Technical Article: Time to Rebuild? - Part II

buy the book - it will save ya a lot of grief

[85911]

For your reference, here's what I got on my 1985 911 last October with 67,353 miles. It runs great including at a DE, doesn't leak any oil, and starts right up.

compression:
#1- 175 psi
#2- 180
#3- 180
#4- 177
#5- 180
#6- 180

leak down test:
#1- 2.2%
#2- 0.0
#3- 2.2
#4- 3.3
#5- 1.1
#6- 2.2