I did some damage to my motor on the dyno last weekend, and I got a chance to run a leakdown test.

The motor was completely cold when the test was ran, and I came up with 10% 10% 15% 10%

Here's my setup: benson sleeved b18c, 9:1 cp pistons, stock bore. Stock GSR head, full-race t3/t67

I pulled the head today and put gas in the combustion chambers... the one cylinder with the 15% leakdown had gas running out of one of the exhaust valves.

I know that running a leakdown and compression test will yield higher numbers on a warm motor, because the rings have had a cahnce to expand due to the heat. My question is: how much better will a leakdown test be with a warm motor over a cold motor? Will a 10% leakdown across the board be acceptable on a completely cold motor such as mine?

 

those numbers dont sound too bad for a cold motor at all, especially on a built one thats gonn have a lot more clearance than atightly sealed stock one

 

I think warming up the motor will help the exhaust valves to seal more than it help the rings. A 10% leak is good or bad depending on where the leak is occuring. You can have a 20% leak out the exh valves and the car will still run fine. However if you losing 6% out the rings the motor is shot and it won't run well.

 

Any thoughts on how much the values will be affected in a hot vs cold motor?

 

Anyone?

 

boosted-hybrid: "I always comp test engines hot and leakdown test engines cold. The leakdown test does not vary significantly when the engine is warm. It's a shame that you didn't let the engine go up to full heat and then do the leakdown test. The leakdown would change maybe 1-2%. "