[saltypengu]

Just bought a decently clean 91 S13. The last owner was not a good mechanic.

When first bought the car was completely out of time. Had a new head so assumed timing was off. 180 out and distributor was not installed correctly. Fixed all timing concerns. Vehicle start and ran and missed in cyl 4.

Tested compression all were 150psi except for #4 which was at 90psi.

Found old head had timing chain guides broken on old head, probably why he bought a new head.

Pulled head, found head bolts not torqued at all, almost finger tight, found piece of metal gasket connected to the head carving into the block. machined head and block replaced gasket, put all back together.

Now have 120psi in cyl 4. Still probably too low. Runs a bit better. But still misfiring.

Any ideas on what could be leaking?

My thoughts are it's a toss up between valves and piston rings.

What's the best way to determine which I should replace?