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School Of Hard Knock

Posted 12/1/2012 15:52 (#2727081)
Subject: 855 cummins engine overhaul

just a tish NE of central ND

What are there things to be aware of when overhauling a 855 engine?I'm thinking about doing mine myself right in the tractor frame. The bottom end should be fairly simple and I may have to get a experienced helper for setting the overhead. I'm looking for advise on special issues that may arise,certain ways to do things, ring alignment.....and wear points that may be overlooked such as ways to determine things that need fixing and general cautions......The fuel pump and injectors are low houred so I should get by with what I have with no repairs on them(3-400 hours)Not sure what I will find in the heads though as I don't think they were looked at in probably 6-7,000 hours. The cam has probably ? 1500 hours on it?So I think it may check out OK.....We will see.
Yes, I will get a shop manual for it before I start.
Can the 855 injectors be checked? MINE WERE REMANS and improved the engines starting, but sometimes I still question them if they are operating like they were designed to do.

Edited by School Of Hard Knock 12/1/2012 16:08

farmechspector

Posted 12/1/2012 16:18 (#2727112 - in reply to #2727081)
Subject: Re: 855 cummins engine overhaul

ECMN

The fleet shop I used to work in just bought Cummins Re-man heads. Looks like a quick search shows $200 a piece and up. I'm sure a good cylinder head shop could fix them up as well. Just compare prices.

Edited by farmechspector 12/1/2012 16:19

jimgen

Posted 12/1/2012 16:20 (#2727116 - in reply to #2727081)
Subject: Re: 855 cummins engine overhaul

central mich

It depends upon the condition of the engine at the time of overhaul. If the main and rod bearings are in good condition i.e. no copper showing then the crank is prob. ok. You need to inspect the crank and plastigage when installing bearings. If you are doing an inframe then the cam followers would not have to be set again. Follow the specs in the service manual. Make sure you get the liners set according to SM. We used to use Cummins reman heads, then later we did our own but now shop them out. We always in stall new valves, rotators, guides, etc on the heads. Check oil pump clearances/specs. Really check all specs, check the liner seats, deck height, keep everything clean and if you dont know how to do something find someone who knows. We would install reman injectors esp mechanical engines.
My mechanic is doing a red top 500hp electronic right now.

School Of Hard Knock

Posted 12/1/2012 16:34 (#2727132 - in reply to #2727116)
Subject: Re: 855 cummins engine overhaul

just a tish NE of central ND

Rods and mains have always been changed out every couple of thousand hours. They looked pretty good when we changed them last time. Will know more when I get it opened up.

towman2000

Posted 12/1/2012 18:26 (#2727274 - in reply to #2727081)
Subject: RE: 855 cummins engine overhaul

SouthCentral WI

I'm just going to throw out my thoughts and leave them at that.
Never cared for Cummins reman heads, find a good engine shop and get them done.
Replace the orings in the rocker boxes.
Get a reman assy drive.
Replace the bearing and seal for the assy drive in the front cover (locktite this bearing in)
Get a reman pump from a reputable diesel pump shop
if it is a big cam and the follower boxes don't leak and the followers look good from top and bottom and the cam lobes are in good shape( can be checked with a dial indicator) leave the cam alone (the bearings will be in good shape if the main have always looked good)
replace harmonic balancer
Probably a lot more, but that all that comes to mind right now

oh and one more thing (This will cause a controversy)
In a big cam engine,--- leave the rod and main bearings alone except when overhauling, Rolling bearing between overhauls is a waste of time and money. If you are changing your oil, watching your oil pressure and there are no contaminants (water) in the oil, the bearing will outlast the rings.

luckyman7m

Posted 12/1/2012 19:00 (#2727344 - in reply to #2727274)
Subject: RE: 855 cummins engine overhaul

i agree with the replacing bearings thing. Had a deere engine in tractor that had 16,100hrs on it and factory bearings still in it and no problems. The piston broke top is why we overhauled it. Also the rings on 4 holes were in broke so rings will break before bearings wear out if properly taken care of!

IADAVE

Posted 12/1/2012 19:27 (#2727392 - in reply to #2727344)
Subject: Re: 855 cummins engine overhaul

Depends on how hard you run it. I had one that was a hard runner and the bottom end was shot at 400,000. Probably was due to the fact that there was no governor and oversized injectors, cam timing advanced , etc. Engine never did use oil. Put bearings in a big cam 3 350 that ran stock for 500,000 and couldn't tell them from the new ones.

knks

Posted 12/1/2012 19:41 (#2727425 - in reply to #2727081)
Subject: Re: 855 cummins engine overhaul

haskell county, ks

i don't do much on overhauling diesel 855 but have done many on natural gas and the only thing different is really injectors. good thoughts above but would add make sure you recon rods and make sure you know exactly what you are doing on injector overhead or you will ruin camshaft. cummins were hard on rod bearings in the older small cams so be diligent on checking tolerances on crank. make sure you check cam closely as that is another soft spot on cummins, especially on the injector lobes. we don't use the injector lobes on nat gas so can use those cams with bad injector lobes and have seen a lot of cams with bad injector lobes. cummins are a good simple engine to work on just get manual and follow instructions. might also change oil cooler as they can fail and push oil into water. these need to be put in correctly also and info is in manual.

scott nelsen

Posted 12/1/2012 20:01 (#2727450 - in reply to #2727425)
Subject: Re: 855 cummins engine overhaul

Leeds, North Dakota

http://www.agkits.com/ excellent kits, Dave's diesel can run pump, don't think so on injectors, Steve put new thermostats in it and waterpump, if cam is flacking should be able to see from bottom, roll the motor over a couple times, while someone looks, Scott.

School Of Hard Knock

Posted 12/2/2012 00:47 (#2727979 - in reply to #2727425)
Subject: WHAT FIRES A NATURAL GAS CUMMINS ENGINE? Spark plugs(LOL)

just a tish NE of central ND

knks............How is a natural gas 855 engine timed and fired without injectors????(obveiously injectors are useless for natural gas)...... but what takes care of your timing and ignition with natural gas ina 855?
Just wondering.......

towman2000

Posted 12/2/2012 09:18 (#2728232 - in reply to #2727425)
Subject: Re: 855 cummins engine overhaul

SouthCentral WI

I only change the oil cooler if it has an issue. Have had new ones crack in the first year, had old ones run forever. As I get older I find that I am slowly change my opinion on changing parts simply because their old and I'm in there in. Getting to the point, if it's not broke, why change it.
Towman

Maybe I'll ask that on on new thread

seedcleaner

Posted 12/1/2012 20:35 (#2727504 - in reply to #2727081)
Subject: Re: 855 cummins engine overhaul

Mid-Missouri

Replace piston cooler oil nozzles.

twraska

Posted 12/1/2012 22:20 (#2727733 - in reply to #2727081)
Subject: RE: 855 cummins engine overhaul

Wallis, TX

Make sure you get a service manual and run the overhead correctly, I had a 'mechanic' do one this summer and he bent every injector push rod in the engine. The manual isn't very clear and you have to read it a couple of times for it to make sense, but all in all its a pretty easy job to do.

Edited by twraska 12/1/2012 22:23

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