ssgt highboy

got a head scratcher...any ideas???

I have a 76 f-250 "highboy" with a 390 modified. the engine ran well and strong, just really flat. so we were screwing around with it, tried to put a whole new exhaust on, and ended up breaking 8 bolts off in the heads. long story short, the whole thing snowballed on me. got all new valves, valve seats and seals, shaved the heads and cleaned up the intake manifold. new lifters, rods, springs and a more agressive cam (not wild, but has a nice cam lope to her). new timing chain, and pretty much everything else that needed some tlc was changed. now she runs great, the cam and lifters broke in beautifully. doesn't leak a drop, until i put it in gear. it pumps oil up and out of the top of the dipstick. and a lot, on the 1.5 mile test run, it leaked about 2 quarts out. i thought i snapped a ring, but the compression test was good, along with all the vacuum tests we did. also, the pistons and rings and cylinder walls were suprising spotless, not a mark on them. i'm freaking stumped, especially because it runs so rock steady, even while leaking. any ideas or suggestions would be greatly appreciated.

jonnydesert

did you check for a clogged pcv. if your crankcase ain't gettin proper ventilation, it will force the oil out, no matter how well you built it

ssgt highboy

yeah, no clogs. even with a new pcv valve and the breather off, still does it. starting to wonder if i'll just have to tear it all back apart and rebuild the lower end too. thanks

chipset

I'll tell you why it's happening. the engine is developing serious blow by pressurizing
the crank case. there could be a 1000 things that will cause that. You said the pistons and cylindars were spotless ? They had better not be. they should have major cross
hatches and deglazing. Was the bore measured for taper ? Is the bore worn to the max ? How much was shaved off the head ? Anything over .030 you have the shave the manifold. I take it you didn't take the bottom end and pistons apart. This is just a few things that could go wrong. there could be 994 more things. did you cut the ridge out of the cylindar when the head was off ? sometime the piston will move after the
head and gasket are replaced and the piston will hit the ridge and crush the upper and
middle ring land. What is the compression ? Are you sure the engine wasn't 2 qts. over full before you tested it ? Did you get the head bolts mixed up ? there is one bolt that has to go into only one place. You have massive blow by. the engine has to come apart. Without seeing the engine and actually knowing what you did this is all a guess. Here is the lesson learned. A car motor is as close as you will ever get to a perfect machine.
When one part is worn everything is worn. You cannot rebuild the top end without rebuilding the bottom end and the other way around. the exception is if something actually broke and you need to replace one part. bottom line, the bore has to be measured, the pistons have to be measured. Good luck.