When I try to compress the cycinder to keep the valves from falling in the air just leaks out. When I do a normal compression test with the head together I don't have this problem. Anyone have any ideas on what I am doing wrong?

 

are you putting the cyl. at tdc? its always gonna leak a little, you need a constant supply of air.
You can also put strings in the cyl. to keep the valves from dropping

 

Yes, cylinder is at TDC. What PSI should I use on my tank? I didn't know I needed a constant supply. I though I could just blow it in and it would stay.

 

i dont know how you are gonnado thatwith the head on the car. valve seals are a bitch period

 

I got it. Nevermind. Thanks though.