Advice on Overhauling MEP803A engine

Rangatira

New member
4
2
3
Location
St. Petersburg, Fl
Guys,
I have an 803 with poor compression. It was apparently swamped. Demoh and I pulled the head tonight and found very light pitting on the cylinder walls. My options are to replace the engine or overhaul.
Can anyone lead me in the right direction for surplus overhauled Dn4m engines?
Can anyone share their experience honing the holes on these with success?
Is there someone that you guys recommend for rebuild kits other that Green Mountain or Ebay?
 

jamawieb

Well-known member
1,257
142
63
Location
Ripley/TN
Guys,
I have an 803 with poor compression. It was apparently swamped. Demoh and I pulled the head tonight and found very light pitting on the cylinder walls. My options are to replace the engine or overhaul.
Can anyone lead me in the right direction for surplus overhauled Dn4m engines?
Can anyone share their experience honing the holes on these with success?
Is there someone that you guys recommend for rebuild kits other that Green Mountain or Ebay?
If you have little pitting just hone the cylinders and add new rings. I've honed some deep pitting and had great success. Had a 803a with really bad pitting and sold it to a friend and told them if it failed I would replace the motor. That was 5 years and 8,000 hours ago, still going strong.
 

Light in the Dark

Well-known member
Steel Soldiers Supporter
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MA
I am not even there yet, to figure out a price. I am not giving up on this yet, as I am sure it can be a good runner... I just keep pushing it off as other (working) machines arrive.

If I do decide to chop it up, I will circle back.
 

Ray70

Well-known member
Steel Soldiers Supporter
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West greenwich/RI
I have had excellent success honing the DN2m's and DN4M's oversized.
I have honed them up to .020" oversized and installed oversized pistons from Mayi Diesel.
They sell .010" .020 and .030" oversized piston / ring sets.
Also, you don't need to do all 4 pistons, only the damaged cylinders.
The motor will never know the difference if 1 or 2 pistons are oversize and others are standard bore.
It took a long time with the drill, but I used a Lisle 15000 hone with the micrometer style head, 60, 120 240 stones, then finished with a 400g ball hone.
I was able to do it in the machine with the crankshaft still in place.
One word of advise... Remove the oil pickup and pressure relief tube and when done power wash the CRAP out of the inside of the motor.
Then power wash it again.
Once that is done, call in a friend to was it a 3rd time! you gotta get it squeaky clean in there.
The first one I honed out I didn't remove those parts and I missed a bit of grit under the pickup and in the back left corner. Started it up and after about 15 minutes it started to loose oil pressure because the grit was wearing away the bearings ( as well as the bottom of the lifters. So I got to rebuild that one twice! new crank, bearings lifters etc... and .020" over pistons.
Once I learned that first mistake I successfully honed 4 or 5 others with no issues.
Get you gasket kit on ebay for like $70 total. No need to buy from Cummins at $400!
 

Daybreak

2 Star Admiral
Steel Soldiers Supporter
1,414
254
83
Location
Winchester, Virginia
Howdy,
Things to remember.
When looking for parts
ONAN DN2M and DN4M all use the same parts (2 cyl and 4 cyl)
Lister-Petter LPW2 and LPW4 is the same engine.
The engines have been around for years.
MAYI Diesel has been my go to for parts.
 

Rangatira

New member
4
2
3
Location
St. Petersburg, Fl
I have had excellent success honing the DN2m's and DN4M's oversized.
I have honed them up to .020" oversized and installed oversized pistons from Mayi Diesel.
They sell .010" .020 and .030" oversized piston / ring sets.
Also, you don't need to do all 4 pistons, only the damaged cylinders.
The motor will never know the difference if 1 or 2 pistons are oversize and others are standard bore.
It took a long time with the drill, but I used a Lisle 15000 hone with the micrometer style head, 60, 120 240 stones, then finished with a 400g ball hone.
I was able to do it in the machine with the crankshaft still in place.
One word of advise... Remove the oil pickup and pressure relief tube and when done power wash the CRAP out of the inside of the motor.
Then power wash it again.
Once that is done, call in a friend to was it a 3rd time! you gotta get it squeaky clean in there.
The first one I honed out I didn't remove those parts and I missed a bit of grit under the pickup and in the back left corner. Started it up and after about 15 minutes it started to loose oil pressure because the grit was wearing away the bearings ( as well as the bottom of the lifters. So I got to rebuild that one twice! new crank, bearings lifters etc... and .020" over pistons.
Once I learned that first mistake I successfully honed 4 or 5 others with no issues.
Get you gasket kit on ebay for like $70 total. No need to buy from Cummins at $400!

Great info. Thank you for the details. I was looking for oversisized pistons and did not come across those guys. I will check them out. Thanks again.
 

1quickduramax

New member
12
2
3
Location
Melbourne Florida
Hey does anybody know where to get any long blocks for these? My 803 block is pretty bad. I’ve talked to the lister pitter distributor and he said they can’t sell whole engine due to emissions, he’s looking into a long block just curious if anybody else has found a good place to buy one. Thanks
 

Ray70

Well-known member
Steel Soldiers Supporter
1,170
1,030
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Location
West greenwich/RI
Occasionally they come up on ebay, but none right now.
Maybe you could find someone with a 400hz 813 willing to either sell it or part it out for a reasonable price??
 
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