Hi guys,

I would like to know , for a 12v rebuilt, if marine pistons could be a good choice. Ive seen the difference between combustion bowl and the marine one is quite bigger, that lead me to think that it could solve the 'mismatch spray pattern' with the 370's.. Do they have the same compression ratio ?

Cheers,
Marc/

 

lower compression ratio...

the marine pistons are sweet... light weight, double reinforced top ring land, and the top ring sits down a lot furthur. much bigger crown, more resistant to high temps, etc.

Forrest

 

do some reaserch.....I dont know the specifics but I have been told from a very reliable source that the marine units arent necessarily the best way to go. Hopefully someone will have more accurate info than I.

 

Red, I run them in my truck with the 370's I can't really do much of a scientific compare b/t them and the stockers but I got them simply because they weren't too much more expensive than the stock set and I figured, if the stockers were designed for 215hp and these were designed for 370 they'd be alot more durable, and everyone that I talked to at cummins and a few shops during my rebuild assured me they resisted the temps alot better. When I put it back together I didn't notice much of a difference in performance, but it definately made a reduction in smoke and my milage went up, I'm sure the rebuild helped, but it was a big big change.

 

Smoking : I probably have a chance to get a set at a decent price, but here's my next question beeing a newbie in the Cummins world.. How to know what bore they have if i just have the cummins part number.. I don't think that i will need to overbore the block, just to drop the pistons in it with a deglaze of the cylinder walls..

I also read that they are greats, but i wanted to ear from somebody that run them into his engine..

Any other inputs are welcome..

Cheers,
Marc/

 

The 5.9L Marine engine and the smaller hp versions in the trucks are the same bore, as long as they're stock Marines and your block's never been bored before then they should fit fine. To be safe you could measure the piston and the bore to make sure they haven't been tampered with(I.E. they're oversized pistons and/or the blocks been bored) Measuring the bore in the block wouldn't be a bad idea anyways to make sure the bores are clean and straight and aren't tapered or oval'd out. None of this would be visable by just looking at it. But you should be able to get acceptable tolerances from a 5.9L service/overhaul manual or maybe just by calling a shop or dealer and asking.

 

if you want to rev the snot out of your motor and you're going to be running high EGT's, get the marine pistons...

if you want crisp throttle response and you're going to keep EGT's low, run stockers.

Forrest

 

I don't want to cross the 300hp marks, so i'll stick with stocker. I wanted to go with marine pistons because the deal was very good...

Marc/

 

Not all Cummins Marine pistons are alike. The best bet is the 370 with factory teflon type coating from the factory. Some of the others are weaker in critical areas. The pin number you need is the stock Chrysler part. Not the 370 pin number listed in the Cummins directory, unless they found the mistake and changed it since last year.

Stock pistons are not as good in strength. Stock are more than adeqaute for most engines though.

 

whats the compression ratio difference between the stockers and the marines? what kind of headaches will they make for cold weather starts sub zero / -30 degree starts?

Wondering if they would be a better option for a twin Turbo'd towing application 450-500hp? Engine came with a cracked piston, cylinder walls are fine but was thinking of other options when i pop in the new pistons. any tips here Don anyone. I see that someone said it made a mild difference with the 370 injectors which is what i have sitting on a shelf but i also realize it may not be necessary.

just curious