Case L compression

About how much compression should an "L" have? I can feel the air coming out with my finger so I know I have some compression, but when I put my tester on it I do not get a reading, my tester starts at 10 psi. My tester works as Ive tried it on a differnt engines. It should have more then 10 shouldnt it? Ive installed new new rings and a few new vales and seated the other valves, planned the head and new head gasket.
 
Piston ring end gap, comes to mind. So often std rings in well wore bore won't seal statically. Ideally try and get around .003/inch of bore. Many times oversize rings should be used and the gap cut down down to size. The old sleeves are usually round, with measureable taper, which shouldn't cause a problem. Piston top groove ring side clearance is always an issue with used pistons. Invariably that top groove should be recut and a spacer installed. This will keep the ring from tipping. Excess carbon build-up behind the rings is usually more of an issue then ring wear itself. Many an old engine is made very usable by knurling the piston skirts to regain proper clearance, recutting the top grove and a slight hone with a rigid, not expandable hone. The very basics such as valve adjustment and cam timing, of course are important. My two bits, while finishing the coffee pot, and avoiding morning chores............
 
Old proudvet; What is knurling of the piston skirts mean. I've heard the term before but never knew just what it meant. gobble
 
You turn the piston in a lathe and run a tool on it which "ruts" the bottom diameter of the piston in a criss-cross fashion. Just like with a muddy road, when you push a tire in, the mud squishes up around it, and the result is a low rut with raised sides. This increases the diameter of the piston to better fit the bore. It isn't as good as a new piston, but will work for a couple thousand hours in a pinch. Then the same problem will come back, only worse. Also, this works well on aluminum pistons, but I don't think it would work well on cast iron pistons.
 
check your valve lash adjustment. if you have them set to tight u will have little to no compression. each cyl. has to be set on TDC of the compession stroke.
 
Tom my computer just ate my reply with a couple of pictures. I haven't time to retype it right now, I've a meeting in town in 45, I'll re post later or first thing in the morning.........
 
Well I went back through and re-adjusted the valves while each piston was at t.d.c. instead of following the books instructions of doing certain valves while certain pistons were up. After I did that I then checked compression doing a dry test, and had 20-25psi at each cylinder. No idea if thats good or bad but at least I have something..
 

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