Rebuild on 300 Cummins

Well to change it over and change it over right, you need to get the CPL from your engine, and the CPL from the engine you want to make it into and compare the parts list.

What CPL do you have? There was one I believe it was 0838 it was a fleet engine that had high-compression Pistons, different cam, different injectors, I believe you even the rocker arms were different. They could be built into 350s pretty easily but you really had to watch what parts you swap when building them. If you intermingled a lot of the parts with that CPL and then the other one you could end up with her real dog that would barely run.

What are you using this truck for anyway? I mean you can build it just the way it was to begin with, drop a few numbers on the botton, add some shims, back off the AFC a bit, and maybe slightly retard the timing and it'll run strong

 

Maybe it was the way you stated the original question but I think we all were a little confused about what you're looking for.

Maybe you can restate exactly what you want to do and why you want to do it.

It would be helpful for you and for us both because you were obviously given very bad information and whether or not bad information was given by the mechanic you know or just by someone else you know or perhaps maybe your reasoning for doing what you're doing is it good reasoning, or maybe it is bad reasoning, but it would be best to just let us know exactly what you want to do and why.

And if you would not mind why is it that you want to rebuild the engine? Does the engine Miss? Does it smoke like a chimney? Is it spitting oil out of the exhaust? Is your engine knocking and the countdown to destruction is moments away?

My guess if this person is going to charge you $4,000 in labor and you supply all the parts and you want to change it over to a higher horsepower engine my guess would be you're probably going to be looking at at easily 11 or $12,000 after you put in all the maintenance items that you're supposed to on the engine. Actually probably more than that.

There's a place that you can buy a whole new crate engine for $11,000. There are ways to get more horsepower safely out of lower horsepower engines depending on the condition of the engine and what it is you're trying to do.

I think the point of all of this is that there are a lot of different ways to approach this depending on what it is that you are looking for and what your reasoning is. Some may be less expensive, some may be a waste of money, some may cost more but be a better decision.

So if you could tell us exactly what you're trying to do and why that is I think we could give you a much more accurate answer to your question.

And also if it has newer heads on it how do you know it hasn't been rebuilt?

 

And the last thing I'm going to say about this right now is if you want to rebuild it purely for more horsepower I suppose that's one thing.

But if that engine has newer heads on it and you pull the pan down and you see those bearings don't have a lot of time on them and you replace them and you replace all of the accessory things on the engine that I said before, as long as that engine runs and doesn't have any miss or burn excessive oil that engine will probably run you for many years. Even if it burns a little oil that's okay. At that point the only thing left is really the liners and pistons and if it's not burning excessive oil forget about it and use it and enjoy it. It will be extremely dependable. If it runs good the accessory items on the engine are going to cause you more trouble than not rebuilding it.

 

That plus check and maintain your coolant SCA levels.

 

The way we used to do them was use a CPL book which I do not have any more. That is critical parts list.
Look at the CPL we had and its camshaft number. Then look for the highest HP engine CPL using the same cam. If it required an offset key look for a bit lower Hp rating if acceptable. That saved a lot of time and money. Then buy all the parts by the higher HP CPL list. Injectors were always different but we just ordered what we wanted and turned the others in. We ever got bumped for that. Not so sure how that will work these days. That built the engine to a factory spec engine and you know it will work properly after it is jig timed.
Lots of folks around here know more than I about above factory power and they do not all agree. Some of them have corrected me in the errors of my ways and or what I thought I remembered. Lessons learned but then I do not agree with some others on the best way as well.
I will end with this: When I was in a Cummins fleet training class for the low cooling system and the N14 which was just about to be released this came out.
Why is the company under Cummings recommendation replacing the the trucks that have 350's with 315's? Engineer put up graphs on RPM, torque and HP. Showed the 350 only made that power in a short RPM range. The 315 maintained more HP and torque over a longer RPM range than the 350. Claimed it would out preform the 350 all day in rolling hills and get better mileage.
While I do not know about all of that be careful what you wish for.

 

So you're planning on using this truck for OTR freight? Like a hundred thousand miles a year or something?

You know that isn't necessarily the best way to make money, or the best way to have a nice life

I'm kind of in the Appalachians too, what state are you in?

 

If I were to build that up to a factory spec engine I would want a 400. Sorry no help on the CPL but made in 1985 or 86. With a 9 over, 3.55's and LP 22.5's averaged 7 MPG. Better than the 350's in the fleet and it passed them all.
A similar O/O set up had several different transmissions put in it over the years. The next to last one ended with a b or P at the end of the model #. It was 22% overdrive with 11R 24.5 tires. He did not keep that long as it was over geared. Had to shift in rolling hills all the time. He ran everywhere, Cabbage and all with no Jake.
Just saying it all has to work together and those were a good fit with those NTC's.
Personally I like 13 speeds but it does not cost a lost of money to make your trans an OD.

 

I get what you are saying and there are a few options.

First I just want to make sure that you understand those engines are generally only rebuilt when they use excessive oil. The bearings are replaced but the actual rebuild is not necessary until you are burning excessive oil. You can be preventative you can make more horsepower but as far as actually needing a rebuild if the engine runs good and does not burn oil it does not need to be rebuilt. As long as the bearings are replaced you can run it until it starts to use excessive oil. I don't know how much money you have to put into this but just understand if that engine runs good and does not burn oil the money you're spending aside from getting more horsepower is unnecessary.

And also I wanted to remind you the most important thing way more important than rebuilding the engine, is all of the accessories on the engine. We talked about this earlier than water pump thermostats clutch fan vibration damper oil Cooler piston cooling nozzle accessory Drive etcetera etcetera. On an old engine way before ever having to rebuild it and way more of a problem than ever having to rebuild it are those accessory items they must be done if you want to be dependable. Doing a leak down test and all that stuff also.

Now as far as your options go if the engine runs good does not miss does not burn oil excessively you can just put bearings in it and turn the pump up 10%. 10% is safe for that engine and you won't have quite 350 horsepower but you'll have between 300 and 350 without spending a ton of money. You can run it like that until you're ready to really do the real rebuild and then up it to 400.

If you really want to rebuild it into more horsepower I think it may be cheaper to just buy a new crate engine. Everything that you're going to do is going to open up another can of worms for something else. So for example when the heads come off to do the liners the block may have damage. That is common on these engines. It can be fixed but it's going to cost you something. The counterbores are probably not cut for lower press fit liners on that engine. So someone is going to have to come out and cut them which is a pretty good expense. If you're going to have more horsepower the camshaft is going to have to come out and set up with the offset key. At that point you should replace the bearings at the camshaft. While it is out the camshaft itself will have to be inspected.

Even though the heads look newer they need to be sent out to a shop they need to be checked and at the very least you need new injector cups pressed in.

You also are going to have to pay someone to time the engine you going to have to buy a new turbo new injectors and you're going to have to have somebody go over your pump. It all cost money. And in the end you're still dealing with an old block. So you would have to price it out but there used to be a place in North Carolina you could buy a whole long block engine for like $11,000. I find it hard to believe that the amount of work that you want to do to this is going to be any less than that.

So if that's really what you want then you have a brand-new block you have a brand new engine and then you're really being preventative. By the time it's installed it may cost you 15- 20 thousand or maybe more if you can't find a crate engine for that lower price, but you'll have a new engine.

Of course at that point you need to replace the radiator mounts and the engine mounts and the transmission is going to have to be separated from the engine and at that point you may want to think about a new clutch and maybe a 13-speed transmission, because you'd be surprised the difference it makes in pulling from a 13 speed to a nine or ten speed. and if you put a new clutch in you probably will need a new clutch shaft clutch brake a new bearing new oil change new Forks probably cross shaft bearings are shot, you need the flywheel resurfaced or buy a new one and probably a new ring gear and pilot bearing then you have to shorten the drive shaft so at that point you should put new universals in also and a rear seal on the transmission.

And if you really going to be preventative you shouldn't put a used transmission in you should go to Fuller and buy a brand new 13-speed transmission. Then you have a brand-spanking-new engine you have a brand-spanking-new clutch you have a brand-spanking-new transmission. Then you are really being preventative.

Now you're pulling power is also based on the ratio of your Rears. I thought I remember a long time ago reading your rears were geared really high or something. If that's the case you really should just buy a modern air ride and put that on the back. Now whether you swap the rears or keep what you have all of the Driveline seals should be replaced, all of the wheel seals all of the pinion seals. And the oil should be changed. All of the bearings inspected. And put new vents on the Rears.

And while we're talking about being preventative, you should have all new air cans all new slack adjusters all new s cams all new drums and brakes, you also want new Airlines where needed and positively replace the fuel lines to the engine because the old ones can collapse internally. You also need a new air dryer and a new governor. And while you're at it any cab mounts and bushings probably should be replaced also.

And don't forget a new radiator cap and a new windshield wiper motor and new windshield wiper pump and wipers of course. If you do not want to replace the blower motor and the heater core, at least put brand new heater hoses on.

Check the hoses for the power steering because they may need to be replaced and definitely replace the steering shaft seal.

Put new shocks all the way around and replace anything in the front end that is needed. Whatever suspension you have in the rear check the Springs bushings whatever you have, I don't think you have air ride.

Of course new batteries new starter and alternator and the correct antifreeze with the correct additives to finish everything off.

I don't know how much money you have to put into your project but if you really want to be preventative and you want your truck to be 100% the things I've listed is what you need to do. The brakes and suspension and front end is every bit as important as anything you do to the engine.

And just so you don't think I'm being smart with you or anything like that, everything I listed is what I did to my own truck to put it into service.

And then some.

I wish you good luck and if you decide to rebuild the engine you have we'll have to try to figure out what parts you have and what you need.