baronbob
08-16-2005, 10:57 AM
This is my first season with a used M-1 (5#psi) installed on my used 7.4 Mpi (600hrs). I have 125-135#'s compression in 1,2,7,&8 and 110-1153s in 3,4,5 & 6. I squirted oil in all the cylinders and found aproximately a 10# increase in all cylinders. The leak down however is 50#s/ 80#s in 1,2,7,&8 and 20#s in 3,4,5 & 6. I can hear leak in the exhaust. I also have oil backing up the dipstick under full power. I plan to pull the heads and re-work if necessary, replace the factory gasket with better gaskets designed for blower applications and re check the leak-down to eliminate gasket and valve leaks. If I still have leak problems I will tear down further to the pistons and rings. I was planning to hone, re-ring and replace the pistons with forged pistons. Any suggestions for pistons/rings. If the bearing surfaces are good is it worth the expense to replace rods? rod bolts? and go to a steel crank? I plan to stay with 5#s of boost and keep my rev limiter @ 4750 RPM. The application is a Bravo III on a heavy cruiser.