Competition Hp and reliability

[Reb.B]

i don't want to scare anybody. I just want to post my findings and maybe something informative might come out of all of this. My truck, at least what it used to be: 24v, tst comp box, DD II's, propane, and B-1. I'm doing the 24v p-pump conversion and pulled the head to check it out, found out it had 21 cracks, so i got a new one, ported it, SS valve inserts, more spring tention, and was going to assemble, but figured it would be best to surface the block when going with copper gasket. So i pulled the motor and pulled it apart and this is what i found. The thrust washer was Toast! i had over . 040 slop in the crank shaft. Also the rod bearrings were really worn. Could see alot of copper. Our motors only have one just bearring and its only on the top side and not top and bottom. This is a problem that we need to look into, better oil, top and lower thrust washer, and better bearrings. Also all the rings were lined up on all the pistons. Thanx, Reb

 

[propuller]

how many miles were on your truck?kurt.

 

[Reb.B]

i have 110K on the odometer, 45K easy miles, 20 semi hard miles, and the rest pedal to the metal

 

[83 crew cab]

how many bottles of propane

 

[Reb.B]

not many bottles, but lets face it, . . there's a lot more guys out there with more HP, ... . ie. twins, huge injectors, crazy NOS, and we are all under the assumption the the mighty 6 cyl, 7 main bearring Cummins will hold anything other than head gasket with too much boost. Thats what i thought at least. We need to keep in mind rod bearrings and the puny thrust bearring, and see if these questions can be answered by making the bottom end stronger and more reliable.

 

[jwilliams3]

I wonder if 3,000 mile interval oil changes will help with these modified trucks??



I guess its time to rebuild once 100k gets here!



Reb,

All 3 rings were lined up on every piston?



--Justin

 

[F8LDOSE]

As for the bearings, i'll be balancing my bottom end in the next couple weeks, curious to see what kind of job Cummins does from the factory..... Were you using an aftermarket cam and/or a ported head? What kind of exhaust egt's were you seeing on a HARD run? The heat has to go somewhere. But still to have that many miles on a motor that has handled that kind of abuse is still impressive. No gas motor will do it. If i get 100,000 miles on my new motor I'll..... well never mind it won't happen.

 

[83 crew cab]

just got mine back from being balanced the rotating massof crank was only off by 4 grams I cant rember what the rods and pistions were off by I will try and post that tommarow