For the record we're talking about a '72 K6 with 5,300 miles.
Okay...well I bit the bullet and tore down the engine a 2nd time just to be sure the rings were installed correctly, i.e. manufacturer's mark facing upward and rings indexed 120 +/- deg. from one another...and I'm happy to report they were all good. I assembled and mounted the engine in the chassis then remembered to check/reset valve clearances to 0.002".
I measured compression (dry) and recorded 80psi in the left and 50psi in the right cyl. (carbs removed). I then added some 10W-40 oil in each cylinder then recorded 120psi in the right and 80psi in the left cyl., still not within spec.
Ring clearance on all the new HONDA brand rings were within spec., I used new std. bore HONDA pistons and had the cylinders honed with a flex hone. Compression was tested w/o the exhaust & carburetors installed, both spark plugs removed and no (or very little) crankcase oil (drained prior to tear down).
Also worth noting is that I cleaned & re-used the base, head and rocker cover gaskets with Yama Bond #5. The engine was not run between rebuilds. Did a leak down test on the head with acetone to verify the valves were seating properly. (I also installed 2 new Viton O-Rings between the cylinder block and head to seal the two rear oil passageways)
So what gives...? Do the rings need to "seat" themselves to develop full compression? Not sure why such low compression and the relatively large variation in pressure between cylinders? Is there a preferred alternative to the HONDA brand rings?
Ring installation sequence (from top to bottom):
Hone profile:
I've run out of items to troubleshoot...any suggestions?
