Which overhaul kit to buy?

[RoadGoesOnForever]

Well, Im going this week to buy a 94 auto motor to rebuild for a conversion project. What year motor overhaul kit should I get and marine or truck version. Any other info such as engine CPL numbers ( I think thats what theyre called) or anything else pertinent will be appreciated. Thanks

 

[NTIMADTR]

Yes I would also like to know what type of engine and rebuild kit I would need. Also If it would be better to buy an engine that needs to be rebuilt and BOMB it or get a good running engine and bomb it. My 6. 5 engine went south on christmas eve "NO REGRETS" I am going to put a 12v Cummins in her just want to know where to find a good eng or just rebuild one. Thanks in advance for your answers.



Thomas

 

[Joseph Donnelly]

Any 94-98 engine 12 valve engine should use the same rebuild kit One of the expensive parts is the head gasket and be sure it is the upgraded marine part that they now use in all engines' kits: 3283335. However if you are bombing you might want to use the thicker ones, 3283337 which is . 010 thicker, or 3283339 which is . 020" thicker. Kits should be available with whichever one you want.



Rebuilding an engine properly is generally the best way to go, but it can be very hard these days. Many small shops that specialized in the best work got shoved out of business by generic low quality shops who do "reman" engines for gassers to the lowest price. As a result you have trouble finding a good crank grinder who will cut the journals to the exact sizes you need with your bearings, get a smooth, chatter-free surface, and index it to exactly 60 deg. each throw. Next is surfacing, and diesels need a very smooth surface on the block and head or the gasket will fail. After those 100,000 plus miles, people think the engine is mint because of all the long-lasting Cummins hype, but you will find the valve seats worn, guides and valve stems possibly worn too, cylinder walls may be fine or may have a cut near the top at the edge of the ring of crud, because the rings have worn out the ring lands in the pistons. The crank may be scratched and scored if the oil wasn't kept clean enough and changed often enough. Most 12 valve heads have some cracks, but if used hot a lot, they may be full of cracks.



To summarize, don't go with generic advice or workmanship. Don't assume the Cummins is tough as a rock and can't have any wear inside. A lot of owners either don't care about maintenance, don't know, or believe the almost unimaginable hype about lubricants lasting forever, brand superiority without thorough, unbiased tests to back up the claims, etc. The Cummins will keep running despite a lot of abuse, but it may not run as well as it should. You can lose 50 hp with a worn-out valve job very easily, for example.



Just to get you started, the gasket set (lower engine) is 3802376. Upper set includes head gasket, and for std, 10, and 20 thicker are 3804897, 3802364, 3802245.

 

[RoadGoesOnForever]

I appreciate the reply (especially from someone who definitely knows these motors). So youre saying when I get a rebuild kit it should have all the updated parts, not parts like it would have had in 94? What if I dont get the rebuild kit from Cummins, will the part numbers still be the same. I will be rebuilding this engine in school, so I have access to a valve grinder, seat grinder, honing machine, all sorts of measuring tools, and a teacher with 11 years of experience in the diesel field. We dont have a lathe for turning cranks, but the motor only has 128000 miles on it, so I hope I wouldnt have to turn it. If it needs it however I will, I wont be cutting corners. Thanks again

 

[Joseph Donnelly]

Some of the gaskets are now pink and supposed to be better than the old black ones. I have seen pink on the gear housing, air intake cover, etc. The main upgrade is the marine type head gasket, the numbers I gave above. I think I'd go with Cummins for the gaskets, probably more expensive but you don't want to do it over. Be especially careful about cleanliness and torque on the head and the oil filter pad/cooler. The head and block surfaces must be clean, use lacquer thinner and be sure all the bolt holes are clean and not filled with oil or something that can be squeezed out onto the deck surface. Your crank will need polishing at a minimum and check it for wear on the rod journals--out-of-roundness from the piston and rod pushing on it and creating wear in that area. Expect the tin coating to be worn off the rod bearings in that area too.

 

[C Schomer]

I've used the pink gaskets and they work very good. Put them on clean and dry! Same for the bluish green gaskets.

 

[NTIMADTR]

Next question Ill ask is would it be correct to bring the engine to an authorized cummins facility to have the machine work done and then take her home and assemble the motor. Or can any machine shop do the work. I have a friend with a machine shop who is good but dont know if the cummins needs special attention due in part because its a diesel. I can see that getting a good used motor for rebuild can serve two things I can have a fresh motor after the rebuild and instead of taking a good motor apart to BOMB it I have a motor apart already that can be BOMBED. Thanks for your help and let me know if ya here anything and ill keep up the updates. .





Thomas