Pistons??

jtlane

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Has anyone had to have their pistons cut down? The pistons I bought was .1 shorter I told the machine shop not to deck it no more than .1 it came back with .38 and to .4 protruding the deck
 

Magnum PD

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Think your missing some zero's.

.010 decked pistons. I had to get .066 thick headgaskets.
 

Magnum PD

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I gotta check to see what kind of protrusion the pistons are suppose to be.
 

Magnum PD

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Cometic sells different size thickness gaskets for their mls. Maybe that can help.
 

DZL JIM

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You don't want to go too much thicker than stock on mls Cometic gaskets, they won't hold.

Back in the day I had had several sets of 7.3 pistons shaved off the tops. This lowers compression changing the power/torque curve. But since then research has proven that bowl work is a better way to go.
 

thatdude

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Alot of guys are really big on this, I've argued up and down that this is retarded.

Some guys will deck down .040 and still do .030-.045 of valve relief. It's silly, no reason for it at all.
 

thatdude

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?!?!?!?!

You shouldn't have to cut down pistons. So this isn't a typo, you have almost a half inch of protrusion? If I'm not mistaken it's suppose to be .014 to .031. I don't understand how you can be at .4... Almost sounds like you have a factory defect with your pistons to have that much protrusion.

As for valve relief, that depends on the cam. I think I went with a stock deck height and .036 valve relief.
 
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jtlane

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The machine shop cut it down way too much I told him I could not go over ten thousands I started off with .021 all the way a cross the board now it's as much a .04 I had .01 shorter pistons
 

thatdude

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No idea what max is. I've seen guys deck them past .040. Ideal protrusion is right around .022-.025.

Hard to know max without assembling the rotating assembly in the block.

I'm just confused about your post because you said you had almost a half inch of protrusion and that's not right at all, that's like factory defect piston.
 

bluedge8

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He didn't post the numbers correctly at first, he has since used correct numbers.

Sent from my SM-G930V using Tapatalk
 

thatdude

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your attitude is annoying for a newbie.

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Anyways to the op. I thought protrusion was .014 to .031. I looked it up, it's actually 0.010 to 0.031. I'm assuming with your numbers you got pistons straight from Mahle and not in a ford rebuild kit? (those tend to be higher for some reason?).
 

jtlane

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The Machine Shop took to much off my block I put all the pistons and done the measuring I started off with .021 cause my pistons are .01 shorter now I'm at .04 I told the machine shop that I could not go over .01 off the block I got it back now I'm at.04
 

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