IDIT pistons
Posting Guru
Joined: Sep 2011
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Thanks for all the ideas you come up with. Your ideas will help Justin push the platform further, especially if we can get some stronger pistons. Have you thought about adding a bit more meat between the top of the piston and first ring? That would give it a bit more strength and some more heat resistance.
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More Turbo
Joined: May 2013
Posts: 597
Likes: 2
From: Prague Czech Republic
I have thought about it, but have to admit I am no expert in that, plus I have never seen the crank, is it a flat plane or cross plane crank? Newer noticed on the pictures but I asume flat plane. Someone smarter has to chime in with ideas about the piston. Thicker maybe means it would cool slower, I do not know, the plan was just to replicate the IDIT piston with regular rings. It all depends when I have the sample so they can get me a quote.
Lead Driver
Joined: Apr 2008
Posts: 6,938
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So sitting here with an IDIT piston, and a NA piston. I can say with 99% confidence that theyre the exact same piston, but obviously the IDIT has a larger pin bore. Which really doesnt leave alot of meat on the lower side of the IDIT piston. Also for reference. The PSD piston has the same meat around the pin as the NA piston. .2605" vs. .1565 according to my harbor freight digi-calipers.
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More Turbo
Joined: May 2013
Posts: 597
Likes: 2
From: Prague Czech Republic
So there is not really much sense to try to cast idit pistons. I thought the idit piston is way different, but obviously I have never seen it in person. At least I thought it has more meat around the pin.
Lead Driver
Joined: Apr 2008
Posts: 6,938
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Well my job title is not piston inspector, but to my eyes and everywhere i measured, they are the same. The only differences i can think of are the pin bore, therefore the size of the retainer, and that the IDIT pistons have a keystone upper ring landing and the NA does not to my knowledge.
Fleet Mechanic
Joined: Apr 2015
Posts: 1,264
Likes: 7
just looked at the 2 i pulled out for comparison
while i am not a slug inspector either,
i deal with measuring on a daily basis, +/-0.0002 is the normal tolerance.
i can eyeball +/-0.005"
looking at the two together, the IDIT piston appears to have been shaven down,
or is cast this way to drop compression for the turbo engine.
all rings appear to be the same thickness.
i did notice the lower oil ring, has been moved up a bit, perhaps because of the larger pin diameter.
i also noticed on the skirt, the faces of the pin hole were not ground down like the N/A piston.
seeing the meat inbetween the bottom of the piston and the wrist pin,(or lack there of)
i would never run a N/A piston.
but i have seen demolished rods with the piston still attached.
now if they were n/a or turbo pistons, i didnt pay much attention
while i am not a slug inspector either,
i deal with measuring on a daily basis, +/-0.0002 is the normal tolerance.
i can eyeball +/-0.005"
looking at the two together, the IDIT piston appears to have been shaven down,
or is cast this way to drop compression for the turbo engine.
all rings appear to be the same thickness.
i did notice the lower oil ring, has been moved up a bit, perhaps because of the larger pin diameter.
i also noticed on the skirt, the faces of the pin hole were not ground down like the N/A piston.
seeing the meat inbetween the bottom of the piston and the wrist pin,(or lack there of)
i would never run a N/A piston.
but i have seen demolished rods with the piston still attached.
now if they were n/a or turbo pistons, i didnt pay much attention
Lead Driver
Joined: Apr 2008
Posts: 6,938
Likes: 13
Didnt measure ring spacing... kinda dumb not to in retrospect, i just assumed. My attention was being paid to the bottom side which is by sight and measurement 100% identical minus what i mentioned. There is no "extra meat" on the IDIT piston. They are new mahle 2243512HA pistons compared to OE 88 NA pistons. Shoulve got a picture i guess, new pistons are now at the machine shop.
Both turbo and NA pistons can be had with 1.94" and 1.95" compression heights. Pretty standard for and also called "rebuilder" pistons as typically the heads and/or block are decked when rebuilding.
Doesnt seem like .01" would do much for lowering compression... hell theres more of a difference between victor reinz and fel-pro headgaskets. That said, milling .01" off the block when rebuilding...
Both turbo and NA pistons can be had with 1.94" and 1.95" compression heights. Pretty standard for and also called "rebuilder" pistons as typically the heads and/or block are decked when rebuilding.
Doesnt seem like .01" would do much for lowering compression... hell theres more of a difference between victor reinz and fel-pro headgaskets. That said, milling .01" off the block when rebuilding...
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Postmaster
Joined: Aug 2010
Posts: 2,554
Likes: 7
From: Northern Arizona
Decking the block .010" changes the CR almost one full point on a standard bore 7.3L. Piston shaving is a little less change because the flame spreading depressions do not change in height.... But if the entire face is cast .010" lower then it would. Lowered pistons are also a good idea to keep the valve clearances healthy. I think OEM specification on that is .045", but with block decking, aftermarket gasket variation, and possibly head shaving without properly adjusting the valve depth you can be in contact territory fairly easily.
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