1986 big cam cummins lovers please click here

I can vouch for Oldskools Big cam, it runs so smooth you can set a cup of coffee on the valvecover...incredible.

 

I'm reviving an old post here...

I'm looking at an '84 359 Pete with a Big Cam 400 (supposedly anyways.) It's been a lot of years since I've been inside a Cummins, but my memory will come back little by little. What I DO remember about a Cummins is, they never gave me anywhere near the trouble that these Cat's have over my life span. They've been a very dependable and lower-cost-to-work-on engine than a Cat to me.

Anyway, I looked this truck over Saturday with a fine toothed comb. The seller isn't what I classify as a stand-up, straight-forward honest individual. Basically a BS artist in my opinion, but that's besides the point. The engine according to him is all "brand new" (heard that before,) and was rebuilt out in Illinois and I wish I could get that place's name and number, but that's unlikely. No tag on the accessory drive, but a good tag on the pump.

My buddy ran the number on the pump and it comes up as a 310 hp, but this guy swears up and down it's a 400, and could be based on what OldSkoolerKW says. There is evidence of recent work done I admit, but the strange thing is that there's a Jake switch on the dash and on the throttle shaft assembly, but I see the harness all zip tied with all 3 spade connectors in it disconnected. I even pulled a valve cover to see if I was crazy...no Jake on this engine.

I asked the seller WHY is it not there?, his reply was, "cuz I wanted all BRAND NEW parts when they rebuilt it, and they didn't have a Jake in stock so I had them take it off." Who in the world does that? Normally you'd just put a kit in it and 3 solenoids ad call it a day. Strange answer...

It has a giant Holset turbo on it, and it sounds absolutely beautiful running, although it's very sluggish at the throttle response. My past experience with that has been it's sucking air before the pump somewhere. I can bring this thing to my Cummins guru who's got over 60 years inside these things and he'll make this thing run like it should and then some, so that's not an issue.

So the number on the tag on the pump represented a 310 HP. I used the VIN off the chassis, called Peterbilt and they verified it was sold new with a 400 Cummins. The only other numbers I see is down on the turbo side below it, toward the bell housing...are those also ID numbers to go off of, or just casting numbers?

 

@OLDSKOOLERnWV

 

Look on the block just below the rear head gasket on drivers side, the serial # will be in the block at the rear corner. Give Cummins that number and they will tell you what it started it’s life as. Give you the original CPL # too.

My engine started out as a 315 hp, but I have all 400hp+ stuff in it. 365, 400 and bigger uses a different piston than the smaller hp engines. That pump could just be something he put on to get it running, or it could be legitimate and engine is only 310.

 

As far as being lathargic on throttle response, Couple years ago mine was getting lazy, I found a bad supply hose between the pump and the remote mount filter.

 

Keep in mind..... a BIG turbo in visual size does not always mean big hp, the 290, 300 had big looking turbos.

A part # from a piston would get you the info you really need, but that would be a chore to get.

I was told the engine which is in my truck now was a 400, I tore it down and found the new pistons matched the part # for the 315 - 350 engines.

 

This is what you are looking for on the left rear corner of the block.

 

On a couple of my previous Cummins, I've found bad fuel lines that were pulling air. I test them by removing them and submerge them in a bucket, and put the air to them and watch the pretty bubbles.

So far this morning, I've narrowed the investigation down to the engine being original to the truck anyways, a 400 originally, based on the chassis VIN and Peterbilt's assistance. That's good at least. Now Cummins is working on some history and is gonna call me back.

I have to get my buddy that I called Saturday and got the pump number written down to give it back to me so I can dig into that even further. It said 310 horse, but you're right...anything can be. I don't see a 310 HP with that massive hair dryer on the other side being a match, lol.

 

If we never learned a darned thing OldSkool, it'll sure be that people will always tell ya what ya wanna hear, won't they?

 

Tell us more about the truck. I had a '72 359 ( in avatar) and a '85 359, both with BC 400's. I wouldn't worry so much about the motor, if the truck is decent, and the price is right, who cares about the sellers BS, the truck should sell itself. 359's are getting VERY hard to find!!!