Leakdown Test Results - Engine Guys Please Read

[arbailey]

I did a leakdown test just to make sure my engine is okay to put a cam in, and here are the results at 100 psi in:

Cyl #1 - 91
Cyl #2 - 94
Cyl #3 - 91
Cyl #4 - 94
Cyl #5 - 94
Cyl #6 - 91
Cyl #7 - 95
Cyl #8 - 95

I have seen lots of articles explaining how to perform one of these tests, but not too many on how to read the results (and even then opinions vary). For example, one article said that 0-5% was excellent, 6-14% was good, 15-20% was poor, 23% + was time for a rebuild. Another article said that 3-5% was acceptable for a race motor, 5-7% for a street motor, 10% is weak/ok, 20% + was shot. On a BMW websight it said that at 15% BMW considers a motor shot. Another said that on a compression test you want all cylinders within 10% of each other, and on a leakdown test ideal is less than 10%. But is that less than 10% on EACH cylinder, or less than 10% DIFFERENCE BETWEEN cylinders? I think either way I'm ok. Keep in mind this is an N/A combo that is a nice weather car only with maybe one or two trips to the drags a year.

 

[CoupedUp]

You're good ... your cylinders are within 5% of each other and there isn't a great lose of pressure either.

 

[vristang]

What readings are going to be considered "passing" are going to depend on what rings are used. Gapless rings should yield less than 5%, when the motor is fresh. When I got stuck with low tension rings, all cylinders were 20%, when the motor was fresh.

Your numbers look pretty good to me.

I am interested in what others say.

jason

 

[87gtconv]

I can bless those readings. They look fine to me. BTW I am no motor man by a long ways!! I have always heard the 10% rule from best to worst cylinders.

 

[arbailey]

Awesome, thanks guys. That's kind of what I figured but it's reassuring to get input from others.

 

[Black1987Stang]

I forget whats a leakdown test again? lol Isnt it when u pump up the cylinders with air wait a certain amount of time and see how much it drops?

 

[arbailey]

Sort of. You fill the cylinders with air but you use a tool like this one to tell you what % you're leaking.

http://kalequip.com/whats_new_detail.php?id=22