The Diesel Garage banner

Big Cam 4CPL 838

12791 Views 2 Replies 3 Participants Last post by  kingcademk
Can this motor be built to 400 if so How? all of the big shots tell me that this motor isn't worth the time and the attention? Someone help me out I'm basically being given this engine
1 - 3 of 3 Posts
Can this motor be built to 400 if so How? all of the big shots tell me that this motor isn't worth the time and the attention? Someone help me out I'm basically being given this engine
this articule is from my ancle bruce wrote along time ago:thumbsup Now we're going to discuss the fleet engines of CPL 838 and 840. They are supposed to be 315 and 350 horsepower, if you're lucky. These engines, in stock form, are very sluggish. They were never meant to be driven by owner-operators. However, when these fleet trucks are sold, owner-operators buy them. Now we have the problem of trying to make a fleet engine perform up to the standards of owner-operators. The main problem with this engine is the high-compression piston, which is 17.0 total. The timing is set at .101 and the camshaft is not used in any other engine. The first time I looked at this engine I thought Cummins engineers made a mistake.

the driver was the first person to bring one of these lemons to our shop to be rebuilt. Naturally, he wanted horsepower. We change the pistons to a different compression ratio, change the timing, turbo, injectors and fuel pump. Our goal was to take a CPL of 840 and build a high-horsepower engine that didn't smoke when it was cold because driver lives in New York City. We obtained our goal and Mr. driver is happy with his engine.

Next, we got a call from Bill Price in Phoenix, Arizona, who happens to have a fleet of CPL 838, 315 h.p. His engine does not use oil and has no blowby. Naturally, he wanted to build horsepower using fuel only. We built Bill a set of injectors going two sizes larger than stock. We installed a liquid fuel pressure gauge and increased the flow from the fuel pump by 25%. This fleet NTC 315 came to life in a huge way. It eats 425 Cats, 444 Cummins and chases his friend, John Albu's, hot NTC 475 twin-turbo from Phoenix to Los Angeles and back. How long is Bill Price's engine going to last? Who knows. It depends on Bill's right foot. So far, it has lived 8 months longer than I thought it would. He asked for power and we gave him power. Since Bill's truck runs so strong we have cut the injectors back to one size larger than stock and still we have fantastic results from these fleet engines:beer.

Last week we installed one size larger injectors in NTC 350, CPL 840, T600 KW and set up the pump 25% to feed the larger injectors. Now John drives a beast. John left our shop and went to New Bethlehem, PA to load 48,000 lbs. of brick. Once on exit 13 on I-80 going towards Ohio he never came out of 9th over. John called us from Ohio and told us how shocked he was at how his fleet lemon now runs.

If you own:swear:swear an 838 or 840 CPL engine be very careful when doing an overhaul. We have had many customers try to reconfigure this engine themselves and end up mixing in the wrong parts. This is a dangerous situation and major engine failure is the result. Also, a lot of customers are taking they're STC engines and are trying to convert them to fixed time engines. This is a very poor practice. The result is shortened engine life and less power. Again, a mismatch of parts is possible and severe engine damage can be the result.:thumbsup:thumbsup
See less See more
  • Like
Reactions: 1
I have a cpl 833 I bought recently. The step timing has been removed, pump turned up, 400 cummins top stop injectors installed and changed to 107 degrees timing.
the problem I’m having is it seems very under powered and won’t even blow smoke. Also the rpm will not come down quick enough to shift efficiently. I see above that you don’t advise Removal of the stc but being that the previous owner did just that now I’m searching for answers as to how to build and what is needed to build this engine to be reliable and strong and run correctly. I’d like to do the bare minimum but I will do all that is necessary.
1 - 3 of 3 Posts