Boring Cylinders??

D

DeepSouthDiesel

New member
Joined
Feb 10, 2010
Messages
40
I no on road tractors and big boats you are able to bore cylinders when they go down. So, you might have say 4 that are stock and one that is bored to .020 or even several different size pistons in the motor. How dose this effect the balance of the motor? Can I do this when rebuilding a 12v Cummins? Machine work these days is not cheep! I am about to start rebuilding a Cummins motor and was wondering what is consider acceptable pratice? Also, I saw a few weeks ago someone posted that there was a great place to buy rebuild kits for these motors. I can't seem to find that post? What other things should I consider when I am rebuilding a 12v motor?
 
i believe you want to talk to snedge on here for a rebuild kit. not sure on the procedures but i've always thought that with motors the more balanced the specs are the better they will run.
 
I think on the bigger engines they just re sleve them one at a time.
 
in my friends dodge we took number 1 to .020 over... in the truck. with a lisle micrometer adjustable hone. its near stock and he works it hard every day still. 45k miles on it now...
i think that as long as pistons weigh near the same you should be good. there are balance pads you can grind off of to make it work... oh and it never revs past 3k... so that is a plus
 
The 8.3L, 855, N-14 Cummins engines have wet sleeve engines. When overhauling, these sleeves are pulled out and replaced with new sleeves and pistons. There are o-rings that seal the outside of the sleeve to the block. My concern about boring and replacing one piston, the other 5 pistons have the same age as the bad piston.
 
jedeka said:
The 8.3L, 855, N-14 Cummins engines have wet sleeve engines. When overhauling, these sleeves are pulled out and replaced with new sleeves and pistons. There are o-rings that seal the outside of the sleeve to the block. My concern about boring and replacing one piston, the other 5 pistons have the same age as the bad piston.
Click to expand...

very true, but in this case we had no money and needed the truck.. 100 dollar gasket set and 50 dollar piston and the hone.. we were out a saturday and 250 bucks....

i wouldn't do it again unless absolutely necessary.
 
24vriviera said:
in my friends dodge we took number 1 to .020 over... in the truck. with a lisle micrometer adjustable hone. its near stock and he works it hard every day still. 45k miles on it now...
i think that as long as pistons weigh near the same you should be good. there are balance pads you can grind off of to make it work... oh and it never revs past 3k... so that is a plus
Click to expand...

.020" over with a hone? in the truck?

that's boss right there :cool:
 
Also without a torque plate the bore will be out of round when the head is bolted on.
 
I don't know about if you can do it. But I don't think I would ever be comfortable with having one oversized cylinder. No, machine work isn't cheap, but neither is rebuilding the same engine again later.
Jeff Mumau (Snedge on here) has the best prices on rebuild kits that I have found so far.
 
Last edited by a moderator:
cummins seems to think it is ok to bore one hole fwiw. I would not do it on a high reving engine though.
 
crewgirl said:
I don't know about if you can do it. But I don't think I would ever be comfortable with having one oversized cylinder. No, machine work isn't cheap, but neither is rebuilding the same engine again later.
Jeff Mumau (Snedge on here) has the best prices on rebuild kits that I have found so far.
Click to expand...

Do you have a link to his site Thanks
 
Timebomb said:
Also without a torque plate the bore will be out of round when the head is bolted on.
Click to expand...

most engines aren't torque plate honed... the Cummins are from the factory, but a LOT of engines aren't... and a lot of overhauled/rebuilt Cummins on the road aren't.

it'll be fine
 
Even the lowly 6B engine can benefit from being bored and honed with a torque plate while the machine work is done..
 
Riflemanusmc said:
Even the lowly 6B engine can benefit from being bored and honed with a torque plate while the machine work is done..
Click to expand...

true but most machine shops wont have the torque plate for this engine, though they can get them... for a basic rebuild it is in no way needed, thats for sure.. i could see if he was wanting to spend a bunch to get a lot of power and lots of miles out of it, then yes torque plate hone it. keep it cheap leave it out.
 
Riflemanusmc said:
Even the lowly 6B engine can benefit from being bored and honed with a torque plate while the machine work is done..
Click to expand...

oh absolutely!!! and they are torque-plate honed when they are originally manufactured/assembled

now, if you wanna get real with it, you should torque-plate hone it with 200-220* water running through the block ;)
 
Forrest Nearing said:
most engines aren't torque plate honed... the Cummins are from the factory, but a LOT of engines aren't... and a lot of overhauled/rebuilt Cummins on the road aren't.

it'll be fine
Click to expand...

24vriviera said:
true but most machine shops wont have the torque plate for this engine, though they can get them... for a basic rebuild it is in no way needed, thats for sure.. i could see if he was wanting to spend a bunch to get a lot of power and lots of miles out of it, then yes torque plate hone it. keep it cheap leave it out.
Click to expand...

Call me overly cautious, but I would find a shop that had the torque plate to do my machine work.
 
I agree... the point is, I'm not surprised that a sub-3000rpm engine runs fine with no problems with a .020" over cylinder that wasn't torque honed
 
I assume since this was done to save such valuable time that the rest of the short block was in tact? Cant imagine honing a cyl. all the way to +.020" and all that metal dust and debre in and around the crank and other internals, Id see no way to flush it well enough. And one cyl. overbore and not the others is just odd, never heard of it and would have never crossed my mind to do so. I suppose in a pinch like already said if the r's are kept low enough it should work but that cylinder will be of some % diff. than the others I would think.
 
You must log in or register to reply here.
Top