Engine rebuild question
 

Hey guys, I got a dumb question. I had to put a new set of rings in my 5.9, I had two broken rings in the #6 cylinder. Anyway, as I rebuilt it at different stages I would rotate the assembly to make sure everything turned fine. I'm currently at the point now with the rebuilt head (maching shop, did this while it was apart for good measure) on and all the injectors but one in (the injector for the cylinder that had the broken rings is being tested). Oil pan is off. I go to turn the engine, and I can hear air coming out from the crankshaft area. I would expect all the compressed air to come out the exhaust manifold which some is. What is coming out near the crank area? I can't turn the engine and stick my head under there to feel where its coming out by myself?

LOL The rings have to seat BUT the cylinder with the broken rings is probably the culprit! Did you have the block bored or honed? If not the cylinder has a wear spot where the broken ring has worn the wall down leaving a gap of .020 to .040 thousands which is plenty for air to escape the cylinder! Did you have blow by when it ran? I say yes and if you start it it will still have blow by! Sorry to bum you out!

I honed the cylinders and measured everything within spec, I bought a dial bore guage to do the job accurately. I still currently have the #6 injector out(its getting tested) so the cylinder that had the broken rings is not building pressure with the injector being currently out. So that rules out the sound is coming from the original bad cylinder. Thanks for the reply, I'm open to ideas.

Hmmm well then your probably OK a slow turn on the crank will let the pressure escape any way it can and since there is no oil and new rings I'd say finish the build! If you really have to know have a friend turn it while you watch!

yeah I guess it freaks me out to hear the gas escaping towards the oil pan, seems like it should just go out the exhause valves. I guess the slow turning of the engine leaves it in the power/compression stroke longer before you turn it by hand enough to open the exhaust valve giving it more time to sneek through the fresh rings. When your trying to correct a blowby problem, hearing it on the engine stand is scarey. Hope the rings break in well, hook her to a trailer and work the crap out of her!

Perfect!:c:

The combustion event will seal the rings, you will always have air bleeding back past rings with the engine not running.