Should I Cut Pistons?

DieselNasty

DieselNasty

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Apr 28, 2008
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Hey guys, I'm building my 12v cummins and I have my whole rotating assembly done already. I have brand new marine pistons and the whole set-up is balanced. My question is should I get my pistons cut for valve reliefs if I want to put in a better cam later when I already have this stuff ready to go in? Is this worth it or should I do this, get it rebalanced and then put it together?

Also would the cut marine pistons lower the compression ratio to much for it to be streetable?
 
no more them .060, if you can't get the biggest .375 lobe cam to fit with that much relief , its the wrong grind. cutting compression is not the way to go.
 
Yea that's why I got that marine pistons. I was just wondering if I should cut them while they are still out of the engine in case I want to use a higher lift cam later. Will this be to much of a bear for a truck sometimes driven on the street with the extra low comp?
 
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Is it an actual marine 370 piston or the mahle 155?

a marine 370 is 15.3 mine has .080 reliefs in it putting it somwhere in the mid 14:1's and I run 32* timing on the street. It dosent like to start unplugged in the cold but it will. Ive started it in the dead of winter after having it sit out in a parking lot all night. cycle the grids twice and it fires right up but when they go off it is a bear to keep running until they cycle again:doh:

the camshaft also has alot to do with how it starts. with a short duration street cam it will start fine. put some .060 cuts in it for future clearence set the timing at 28-30 and roll on
 
i guess you could degree the stock cam (or whatever you have now) to help it start a little better and give it a little more low end. i know in gas motors you can set the centerline at a lower degree to help make up for lower compression. what is the most desirable number guys? 106-108 right?
 
2000wvdodge said:
i guess you could degree the stock cam (or whatever you have now) to help it start a little better and give it a little more low end. i know in gas motors you can set the centerline at a lower degree to help make up for lower compression. what is the most desirable number guys? 106-108 right?
Click to expand...
Center line is just a number , the open and close of each event is what the true number , and understanding this is critical to clearance , and performance ,

Example if you have a 180 intake lobe and install this small street lobe in at around 105 centerline , this lobe if it is mildly aggressive achieve .050 lobe lift at around 8 to 10 degrees ATDC. Add 10 degrees to this event and keep the 105 and the intake lobe achieves .050 at 3 to 5 degrees ATDC. Or keep the opening event in the same location and the lobe separation angle just increases by 5 degrees.
So the answer to you question is “ it depends “
 
Contact "The" Jeff Garmon (Jeff2) on CompD

or

Darren Morrison (Quarterman)

about decompressing 12V's and the benefit's of it!!
 
Well I guess I'm gonna have to figure out where I want to send them. Thanks for the info
 
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