Posted by David Sherman on Friday, May 13, 2005 at 1:00PM :
In Reply to: Hmmm posted by Gordon on Friday, May 13, 2005 at 9:49AM :
The blow-by might not be due to the same problem as the miss on #5. All the cylinders might have worn rings, and it was just the #5 exhaust valve being stuck that caused it to blow a puff of smoke out every time #5 came up.
I'd put the head back on, and check compression wet and dry on all cylinders. For the wet compression test, make sure to squirt plenty of oil sideways through the spark plug hole so it will go down into the cylinder. If dry compression is poor, but oil brings it well up, you need a ring job. I would try to do it with the engine in the truck. I'd mike the cylinders and pistons, and get new pistons if need be, but possibly not. Same thing with the rod bearings. Plastigage them and replace if need be (should be some slightly-over ones available to fill a small amount of wear without having to grind the crank, or just new standard-size ones will work). If valve seats are not pitted, but show some signs of not seating perfectly, you can probably hand-lap them onto their seats the old-fashioned way, after taking them out and checking carefull to see that the stem is not bent or badly worn.
Basically, a slightly tired engine can usually be rejuvenated without a complete overhaul. You don't necessarily have to grind the crank, bore the cylinders, grind the valves, etc in a machine shop just to cure a little blow-by. Odds are that new rings alone will probably do the job. It will take a little while for new rings to seat, so don't be surprised if it smokes for the first couple hundred miles.
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