What pistons to run?

yoshi470

yoshi470

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Well i got my head off my truck the other day after blowing the headgasket due to a fire ring not being seated properly and messing up #6 pretty bad. Looked a little closer at the other pistons and noticed an outline of valves on every piston, dont think anything was hitting but im afraid if i run past 4k something is gonna smack. Im running a hamilton big stick and hamilton springs right now. I figured to do this right so i dont have to worry about it again. Im gonna be putting in new pistons with flycuts and maybe get them coated as well. Would like to run 30-35* of timing if i chose to do so. What piston out there is gonna allow me to do that. I heard of guys running CR pistons with p pump set ups. Will that work or not? Probably just looking at staying with cummins pistons as money is some what of an issue here. Also what are the valve reliefs gonna be cut at with the big stick cam? Any help/info would be great.
 
Yoshi470, I'm having a 2.6 engine built as we speak by Josh Woodruff. He is using CR pistons for a bigger bowl and also opening them up. Plan on running 4500-4800 down the track with 38* plus timing. Also am using a billet flat tappet cam with over .100 valve relief cuts. Call him and he should be able to help you out. Woodruffdiesel.com
 
If it's put together anything like the one I dealt with, good luck.
 
yoshi470 said:
Looked a little closer at the other pistons and noticed an outline of valves on every piston, dont think anything was hitting but im afraid if i run past 4k something is gonna smack. Im running a hamilton big stick and hamilton springs right now.
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So tell me this... why are there outlines of valves on EVERY PISTON??? Sounds like your cam profile is allowing your valves get too close to the piston?
 
The late CR bowl will work with the correct injector, a 155° seems to work well ~ 34° static. However the top ring land on the VP piston is 10mm, and only 8mm on the late CR.
 
Smokem said:
The late CR bowl will work with the correct injector, a 155° seems to work well ~ 34° static. However the top ring land on the VP piston is 10mm, and only 8mm on the late CR.
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So which piston do you recommend Weston for a Ppump 24 valve? Leaving the line at 5000+ RPMs.

Thanks
 
tank21pa said:
So which piston do you recommend Weston for a Ppump 24 valve? Leaving the line at 5000+ RPMs.

Thanks
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A forged piston would be best if the budget allows for it, otherwise I would lean toward cutting and coating a stock VP piston.
 
Most I have seen have been Ross. One thing I am not entirely fond of with the forged piston is most use a flat bottom bowl, not ideal.
 
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Have you had your head or your block decked in the past? On our instructions it asks you to check clearances to make sure there is room. I like to see .045" valve face to cylinder head surface depth. If it is less than that, that might be the issue. Also was it the intake or the exhaust valves that had issues?

If nothing else, you will be fine running a .010" over gasket.

If you have any questions, feel free to hit me up anytime.

Zach
 
So Zach your comfortable with .010 piston to valve clearance? I would not feel comfortable with that close clearance on a engine I'm turning 5000rpm...what happens after the springs are a few seasons old and you break driveline at WOT and the engine revs to 6000+rpms??? Your completely relying on seat pressure to keep the valve from smacking the piston with no room for error.

Correct me if I'm wrong.
 
It was the intake valves doing where i could see the outline. Head has been decked .005".
 
have you ever floated the valves with high boost/rpms before you installed the cam or valve springs.

I have had slight marks on my pistons from valve contact since 2007, its just enough to barely feel with a fingernail, you can hardly see them when the piston are dirty with soot, but if you wipe them off you can see it. They were caused by 60psi sled pulling and a few burnouts at 3600-3700 rpms with a TST comp box. I floated them a few times. Never had an issue since installing better springs.
 
I had the head off a few months ago with the hamilton springs in it and didnt notice these marks.
 
Interesting about your marks on your pistons. You may check your spring pressures and make sure they are where they should be...

As for pistons:

Either modify your stockers (are they SO or HO pistons?) for valve reliefs (cheapest), go to a RV275 piston part # 3800333 (a handful of benjamins thru Jeff), or go with Ross pistons (requires two handfuls of benjamins)...

I run the 3800333 and leave at 5000 rpms, down the track the rpms get back up to 4400-4800 depending on track conditions.
 
Jesse did you have the bowl opened up at all on those pistons or do flycuts? A handful of benjamins doesnt sound bad....that come with rings?
 
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