Hello! I'm building up a "plain vanilla" 2bbl, 77 318 truck engine. I'm confused as to the correct locations, relative to the piston, of the oil rail expander gap, oil rail end gaps, and, the end gaps of the compression rings.
The machinist who did my work has one arrangement, the Mopar shop manual has another, the Don Taylor Small Block Mopar book another(and an alternate too!,the army TM ( it's in an army ambulance)reprints the factory info.,a different auto machinist still another method... boy am I confused.
All agree though,except the Don Taylor alternate method, that the oil rail expander ends meet over wrist pin, facing forward.
My concern is,I want a strong running,long lasting engine. I know in engine design,power stroke down thrust, upstroke piston travel,cylinder oiling(and cooling)are all considerations here, end gaps are important. I don't want premature wear,or blow-by.
What are your recommendations?
Thanks!

I've always used the Don Taylor book, I've had it for decades and its basic stuff but I find my self referring to it regularly on occaision. I think with everything offset you would be OK & I believe compression rings do migrate

I've built many Mopar motors from mild to wild, from stock rings to the latest, greatest trick of the week rings sets. I've dyno a bunch of motors that I was able to take apart and inspect after successfully dyno testingthem All of the the ones I've inspect after beaking them in had the rings move a bunch during the engine break in procedures
My main message is to put one oil ring gap over the wrist pin, put the other one above it 180 degrees over the opposite side of the wrist pin, then put the second compression ring about 120 degrees away from the top oil ring gap and put the top ring about 120 degrees away from the second ring gap On the ring end gap a little (.002 to .007)to wide is way better than a tiny bit(.0005) to tight
Good luck on your build.

Thanks guys! The machinist who did the work on my engine, and I've been dealing with his shop maybe, 40 years now, did tell me, when I asked about where to put the compression ring gaps, said " put 'em anywhere, but just stagger them-they move all over the place". I guess he's right.