Will intial compression PSI numbers be lower on a engine not run?

I squirted oil into the cylinders and got 150ish on 2 cylinders. Before the cylinderhead and gasket was changed I got
200+psi on the cylinders. The compression ratio is 10.1:1 and now w/ pistons its suppose to be 10.4:1.

The engine has only be turned over and not run yet so I was thinkign the gasket has to seat or something to get the compression up, since it hasnt been to operating temps yet.

Any ideas?

Check compression without a lot of oil in the cylinder---then check it again with several squirts of oil. If it increases on the 2nd test, you have ring seal problem. If it does not, it is in the valve train.

The head gasket should seal right off the bat, without any run in or warm up--unless something has changed with head gasket materials that I don't know about.

A new build eng can have less compression at first, then compression should gets a bit better as rings wear in. Not a lot, but a bit.

quote Originally posted by maryjane: Check compression without a lot of oil in the cylinder---then check it again with several squirts of oil. If it increases on the 2nd test, you have ring seal problem. If it does not, it is in the valve train. The head gasket should seal right off the bat, without any run in or warm up--unless something has changed with head gasket materials that I don't know about. A new build eng can have less compression at first, then compression should gets a bit better as rings wear in. Not a lot, but a bit.

The head has 39k miles on it, the bottom end has 28k on it. Both havent been used for a few months. Im using ARP Headstuds and was worried I didnt torque them enough. All aluminum engine/head and I torqued to 65ft/lb.
I would assume I should get over 200psi.

Could valve lash adjustment be a factor ?

quote Originally posted by StockGT: Could valve lash adjustment be a factor ?

I dont believe there is adjustment for for valve lash on these motors