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I completed cylinder head/rocker/valve installation and installed my spark plugs today. Then I decided to start turning the crank to see how everything worked and what the compression felt like. I quickly discovered that the intake valve on cylinder #3 was letting air easily escape on the compression stroke with the valve fully closed.

Here is a video I filmed this evening of what I'm describing.

https://www.youtube.com/watch?v=dzyMxkS5LfM

My question is, is this normal? It seems to me that the valves should be sealing pretty much as completely now as they would be after the engine is broken in. I would not expect normal compression numbers since the piston rings aren't broken in yet, but do the valves really need the same kind of break-in?

I show in the video that my valves are adjusted correctly at the rocker, i.e. the rockers are not preventing the valve from fully closing. I've shot shop air into the valve when open to try to clear any debris, but I do not see or feel anything in the way. My next step may be to pull the cylinder head and inspect the valve from the other side, but wanted to post here first for any additional thoughts/advice. This is a new Turbo Aerovee kit.

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Rynoth wrote:I completed cylinder head/rocker/valve installation and installed my spark plugs today. Then I decided to start turning the crank to see how everything worked and what the compression felt like. I quickly discovered that the intake valve on cylinder #3 was letting air easily escape on the compression stroke with the valve fully closed.

You might want to read these two posts of mine:
http://www.mykitlog.com/users/display_l ... 064&row=26
http://www.mykitlog.com/users/display_l ... 600&row=18

I now have 70 hours on the engine and all the valves appear to be working normally.

It looks like I may have received a bad head. I pulled the head today, then took a flashlight and shined it at the piston-side of the intake valve, then looked inside the intake port. Here's what I saw:



I confirmed that the valve and seating surfaces are completely smooth and free of any debris. My best guess is that the valve seat is not 100% centered with the valve guide. Will contact Aeroconversions for a replacement.

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An easy way to test valve seating is to after building the head, valves, springs, keepers, rockers etc., is to level the head upside down on any surface and pour in gasoline, filling the internal head surface area. If any fuel whatsoever leaks past the valve seats now is the time to perform some valve lapping. Judging by some responses valve seating is akin to ring seating which is not true. They are different animals. If by performing this easy test there is no leakage of raw fuel past the valve and seat you are good to go.