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shadrach74 · 12-26-2012, 11:15 AM

A leak down check is a single data point and can often change one day to the next. What was the impetus for doing a leak down test? Is the car using a significant amount of oil? Is it down on power? Oil fouled plugs?

In the aviation industry we do compression and leak down checks annually at a minimum and in many cases every 100hours of tach time. The readings go up and down from check to check but should stay within a certain acceptable range. In aviation, more than 12.5% (70/80) gets a second look as does a variance of more than 7 percentage points. I'd be willing to bet that you could find factory new auto engines that have leak down values in excess of 10% (hopefully not Porsches). I'm sure Jake has his reasons, but his numbers seem a bit conservative to me, but then I've never built a Porsche engine, just aero and motorcycle engines...

If the engine is running reasonably, I'd not tear it down solely based on the numbers you've posted...

12-26-2012, 11:15 AM	#3
shadrach74 Registered User Join Date: Jun 2012 Location: Frederick MD Posts: 658	A leak down check is a single data point and can often change one day to the next. What was the impetus for doing a leak down test? Is the car using a significant amount of oil? Is it down on power? Oil fouled plugs? In the aviation industry we do compression and leak down checks annually at a minimum and in many cases every 100hours of tach time. The readings go up and down from check to check but should stay within a certain acceptable range. In aviation, more than 12.5% (70/80) gets a second look as does a variance of more than 7 percentage points. I'd be willing to bet that you could find factory new auto engines that have leak down values in excess of 10% (hopefully not Porsches). I'm sure Jake has his reasons, but his numbers seem a bit conservative to me, but then I've never built a Porsche engine, just aero and motorcycle engines... If the engine is running reasonably, I'd not tear it down solely based on the numbers you've posted... Last edited by shadrach74; 12-27-2012 at 03:03 AM.