I need a little advice on my engine

[RFazio]

I have a 6 with a Lycoming O-360 A1A. I just performed my first leakdown test at 120 hours on my engine. The engine was a new one. I found three cylinders were at 80/77, 80/78, 80/79. The number 1 cylinder was lower though, at about 80/70. It's got me a little nervous as I can hear the leak at the exhaust valve out the exhaust pipe. I know I'm supposed to run it for another 10 or 20 hours or so and then check it again. Problem is I was supposed to fly down to Sun & Fun in April. I'm having second thoughts now. Anyone have any suggestions or ideas? The Sun & Fun trip is 6 hours each way for me from New York. I feel like pulling the cylinder and checking out the valve. I don't mind flying a few hours near my airport but I think a trip is pushing it. Is 80/70 bad? Should I worry?

[Mel]

70/80 is not a bad reading. I understand your concern that it is different from the other 3 cylinders. My guess is that you had a small piece of carbon holding the valve open.
I would run the engine and not worry.

When you get a reading like this, try removing the valve cover and striking the valve with a "soft face" hammer. Many times this will dislodge any particles.

[Toobuilder]

Yep, I second Mel's advice... I have "saved" many cylinders by staking the valves.

[Dmadd]

or just fly it at full throttle for about half an hour...

[aerhed]

That means you've got an exhaust seat not fitted perfectly and it will slowly get worse until the exhaust cuts a track in the seat. Then it'll dump to near zero compression, maybe 30 or 40. New cylinders are rarely lapped anymore. "Blued to fit" is what you see. Not as good. I know some piston heli operators that tear-down all their new cylinders for fitting before install. Really ups their reliability. You've probably got more than enough time. It takes quite awhile for new valves to dump even when not perfect. Trick: Unspring the valve in place using rope trick, Drop exhaust tube, smear toothpaste on valve face with pinky and lap by hand by pulling/twirling valve stem. On new valves/seats this will often give you a perfect fit. Won't work on worn rounded interface so much.

[RFazio]

I heard about staking the valve but wasn't too sure about trying it. I guess that is the easy first step. If that doesn't work I'll try aerhed's advice. I thought of trying to lap the valve in but figured I'd have to remove the cylinder. I like the pinky idea. I'll let you know how it turns out. Thanks again guys.

[az_gila]

...your compression numbers were obtained with a "Lycoming recommended" 0.040 orifice in the compression tool, and not a 0.060 orifice.

If the larger one was used, then you have really bad cylinders....

[RFazio]

I used the correct size. Thanks