#8 Piston height?

[Dezman125]

Here's the setup
I"m doing the final clean up on the block,turning the engin over by hand cleaning as much gunk out of the cylinders i can. Then i notice that # 8 piston dosn't come up like the rest,stops aprox 1mm below the deck.Did onther complete rotation watching all others,and they all come aprox flush.
Have no history on the truck other then the 64K miles is original,and the block heater was hanging by the cord.
Anyone ever have this on thier engin?I can't see this being factory spec's? I can understand them alowwing more clearance on #8 for heat.
I have my suspicion of whats wrong,but would like hear from the wealth of experiance that frequents this forum
Thanks

[grape]

have you had the pan off. The only thing i can think of is a rod bearing gone.

[Dezman125]

No the pan is still on,just found it befor my "play time" was over and had to go home.One other thing i for got to mention,The line on the cylinder where the ring comes to is also lower,so it's been running like this for a while.
Was looking forward to getting it running,but it looks like i will have to pull the pan. It's not a bearing,i ran it for about 10 min,after i replaced the heater,it then started to smoke bad on the other side,it had a cracked head. The pass head was fine.

[Peter J. Bierman]

My guess is a bent connecting rod coused by liquid stroke or so.
Seen it before, no other visual damage just one piston lower then the others.

One other possibility is extreme clearance on big or small end bearings, you can see by turning the crank a bit fore and aft without the piston moving.

Good luck,

Peter

[Dezman125]

Peter
Pulled the pan and sure enough was bent rod.Other than that it looks like new inside. The previous owner must of been real good at changing oil.

[Peter J. Bierman]

Pull the rod and replace it with new bearings and you be as good as new smile.gif

Peter

[Dezman125]

Hi Peter
I was woundering about the bearing,Havn't had a chance to work on it the last two days,My daughter and i both got a stomach flu and am just getting mobile again.I did order timing gears,and main brearing girdle kit.Was in the plans anyhow and i figered that i was so deep into it now,i hate to do things twice.
Like i said the inside looks like it is new,very clean,no cracks in the webs.I have anther engin which is the same casting on the block,am going to use a rod from it.
I am a little concerned about the top of the cylinder,seems to be a bit of a ridge,may only be carbon,but i'll know more when i get the piston out,hopefully tomorrow i'll be up to working on it.Any thoughts on cleaning the ridge off if it is there?
For the bearing,i understand that GM custom fits all bearings to get the tolarances? Or can i take the numbers from the old one? If the bearing looks good,no uneven wear,or abnormal paterns,should it be replaced?
Appreciate any advice,this is my first GM diesel,and the first GM diesel that i have worked on.
Thanks

[Peter J. Bierman]

Since it has been running ok for a wile with the bent rod, I think the crank is ok. Inspect it anyway and if no visible dammage you can assume it is good. Take the old bearingshell and new connectingrod to a diesel rebuildshop and they shoud be able to supply you with the right new bearing. Put it in and plastgauge it to check the tolerance if you want to be sure.
The ridge can be honed out with a hand hone but if only carbon, just a piece of fine sandpaper will do.

Good luck,

Peter

[Dezman125]

Peter
Pulled the rod and piston last night,I'm going to try to take the ridge out with a ridge cutter,it's not much but i'm sure it wouldn't do the ring any good to be hitting against it.Then i'll touch it up with a hone.Both engins have same bearing#soiwill order one thru the GM dealer in our neighbouring town.
As for Diesel shops,there arn't any around here,i have one of the two garages in our town,one of the drawbacks ;) of living in the North,Isolation :D Mail is fast though recived my gears and girdle,and tach yesterday,so once again i have lots of work to do

[Peter J. Bierman]

So what are you doing here then?
Lets go to work! :D

Peter