Jeeps Canada - Jeep Forums - #2 Piston Pics - Got it out!!! Need feedback

Likely.

I did mention I would be worried about a pounded crank or rod journal.

If it was Mine I would be checking it out.

Mike

twaldron wrote:
>
> If that amount of suction ruined the rod bearing, and likely the
> adjacent mains, wouldn't the crank be out of true?
>
> Mike Romain wrote:
>
> > Ok Bill, just got back from a bush run and read the thread and looked at
> > all the photos....
> >
> > Here is my $0.02 for what it is worth. ;-)
> >
> > Man, that set of photos sure looks like a classic case of gas wash
> > killing one cylinder dead. Big Time!
> >
> > The gas washing all the carbon out and cleaning the rings so oil comes
> > up and gets flash burnt when you change plugs and it fires for a while.
> > While it's firing that flaky varnish looking crap builds up from the
> > burning slurry.
> >
> > Then the build up finally kills the spark.
> >
> > No spark, so on a normal compression or firing stroke, the cylinder is
> > in a vacuum mode and the piston needs to be pulled down against that
> > vacuum rather than the spark firing the piston down.
> >
> > The vacuum must be released or the engine will up and stop.
> >
> > 'Some' oil will be then sucked up past the rings and sucked down past
> > the valve guide seals when this is happening, whichever is looser. Hmm,
> > valve guide seals maybe eh? So when it shuts off, the vacuum sucks oil
> > down from the top, then it mixed with some gas to be thin and ------,
> > ------s across to the spark plug threads. Hmmm....???
> >
> > Now the poor old crank which sounds like a 10/10 is not used to or
> > designed to have any piston under suction, the piston is under spark or
> > intake or exhaust, no vacuum motion involved.
> >
> > Check on top of the oil filter on the block boss for a letter. If M and
> > P are there, it is a factory 10/10 crank which is just 10 thousands
> > under. You can go to 30 or 40 if desperate, 20 is fine. B means
> > factory 10 thou over piston. C means cam 10 over.
> >
> > This vacuum in the cylinder because of no spark means the crank slams
> > down on the bearing and wears the crap out of the center of the bottom
> > bearing on the cap side. The cap side isn't designed for pulling, just
> > being in neutral to the push from the piston rod on spark or sucking
> > from the carb/ TB or blowing out the exhaust which is zip for pressure
> > point wear like is showing.
> >
> > If the engine is newly rebuilt like advertised, the vacuum on the
> > cylinder would be nasty. The compression was way up there, so the
> > vacuum 'was' up there too...
> >
> > Bingo, burned out rod cap bearing and likely both main bearings on each
> > side.
> >
> > I also would be worried the cap and rod and the crank journal could have
> > been pounded out of round from this.
> >
> > I seem to remember a complaint about a timing ping or knock at idle???
> > Hmm vacuum on a piston starting the crank slapping on the bearing makes
> > a neat knock. The bearing can wear away and the knock can lessen or get
> > worse. The first while with the dead cylinder causes the big damage.
> >
> > Then the cylinder is polished up sweet! Well, carbon under heat with
> > gas as a solvent has been sliding around those rings for a while, damn
> > near a diamond polish, eh?
> >
> > No lip, so it 'sure' isn't burnt worn, it is gas washed or gas polished,
> > that 'is' what they look like. I come from the carb days and have seen
> > engines that look like that from short term gas wash. Normally on all
> > or a half bank though, not like injection that just nails one.
> >
> > You need to open some other rod and main bearing caps and post the
> > photos.
> >
> > If those are not burnt out or worn through then the gas wash theory
> > holds, if everything is fried, then it was a dud engine someone sold you
> > or the other person under the 'used' engine tag.
> >
> > If just gas washed, a hone on the cylinder and some new stock 10 under
> > bearings should do the trick. You have to buy the whole bearing set and
> > it is open, so just swap them all.
> >
> > While it is out, that one piston rod should have the cap torqued on
> > properly
> > and be mic'ed out for round. Most engine shops around here charge
> > $20.00 to over grind a rod end or make it true round again and have a
> > bearing to fit.
> >
> > Ok, that was long winded.... Whew... ;-)
> >
> > Mike
> > 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
> > 88 Cherokee 235 BFG AT's
> >
> > William Oliveri wrote:
> >
> >>Got the piston out. Just tapped on the rod bolt a couple of times and it
> >>loosened up. Came right out of the cylinder, no ridge, no problem.
> >>
> >>Here are the pics. Any feedback on the condition of this piston or what the
> >>pic might tell you would be appreciated.
> >>
> >>http://members.bigvalley.net/wuji/je.../piston_2a.jpg
> >>http://members.bigvalley.net/wuji/je.../piston_2b.jpg
> >>http://members.bigvalley.net/wuji/je...berrings2a.jpg
> >>
> >>Thanks,
> >>
> >>Bill
>
> --
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