Finally putting it on the road

Use to drive a 1981 Cabover Freightliner. It had a 300 formula with a straight 7 speed, hated that transmission…..

 

They don’t mind the rpm’s, they just don’t like long spurts of lugging…..

 

The shiny, tiny 290’s used to do the majority of the work back in the day. Only the Formulas were rated at 1900, the rest of the NTC’s were 2100 rates. I took one of my BC1 290’s to Cummins in Joplin one time. Back then they had a guy there that was well known for twisting the brown ones up. I don’t know exactly what he did to it. When I left there it would turn up 2350 and smoked a bit, but it would hang right with the 400’s.

 

Cummins guys all told me if you had those 855’s rail pressured up at all they’d beat the connecting rods right out of them if you ran them under 1700 with a lot of fuel on them. I used to keep mine up 1900 or better if I was being mean to it.

 

That’s true.

It’s hard on any engine to lug it to long. Even my shovelhead Harley, you let it idle at to low of rpm and it will take the rods right out after a while.

The big weak spot though on a hot Big Cam is the pistons and camshaft.

You lug a hot Big Cam, and the pistons will crack in the top of the wrist pin holes.

With continued lugging those cracks work their way up in to the ring grooves and eventually to the top of the piston.

I unfortunately have done it. Not from lugging but from driving with my foot instead of my toe….. I have a piston in my shop that looks like you cut down the side with a torch. Blowed the rings in to….

 

I saw a BC1 400 apart that cut a piston like that. Little wonder, it was in an oil patch bed sow so it wasn’t exactly gently used, and it was run quite a while with the rail pressure up around 225.

 

Was that one of those crazy things that were a Spicer 6spd with a single 4L 4H split to make 7? I cut up a truck here once that had one of those in it with an NT270.

 

No Sir, it was just a big 7 speed. Looking at it, it looked like a 13,15,9 size wise….

 

Better flowing injectors, dual fuel line, mild pump work, good turbo, you can bring it to the forefront without killing it. Just need to use the pyrometer and shift at about 1650-1700.


The pump on my engine now belongs to a friend, it dyno’d over 800 on his engine….