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turning piston diameter down #2465449
03/12/18 10:00 PM
03/12/18 10:00 PM
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gulfport, ms, west mi
rowin4 Offline OP
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A friend of mine has a set of JE gas ported pistons that are .060 0ver .They have lite scratches on the skirts. He's going to toss them. Could they be turned down to a .030 over size? and if so at what cost.


it's ok to butt heads, just don't do it with a butthead
Re: turning piston diameter down [Re: rowin4] #2465469
03/12/18 10:20 PM
03/12/18 10:20 PM
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Is it possible to clean them up at .055" over?

Brian

Re: turning piston diameter down [Re: rowin4] #2465473
03/12/18 10:22 PM
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Pistons are not round top to bottom. AND, there is different diameters, so to speak, at the egg shape. As such, it is not a one cut deal on a lathe.

But, never machined a piston myself, may it is possible. Be interested to hear from real experience.

Re: turning piston diameter down [Re: rowin4] #2465491
03/12/18 10:38 PM
03/12/18 10:38 PM
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rowin4 Offline OP
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I'm sure they would clean up at .055 .I just never heard of it being done or how the piston would beheld to do the turning.


it's ok to butt heads, just don't do it with a butthead
Re: turning piston diameter down [Re: rowin4] #2465509
03/12/18 10:55 PM
03/12/18 10:55 PM
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John Brown Offline
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Years ago I had a set of .060 over oem pistons turned undersized so they would check legal for a NHRA stocker. It was done somewhere in Detroit, but the engine builder never revealed his source. Whoever did the job cam ground them to the same specs as TRW pistons. Going fast in a NHRA stocker was never cheap.


July 19th should be "Drive Like Rockford Day". R.I.P. Jimmie.
Re: turning piston diameter down [Re: rowin4] #2465628
03/13/18 03:23 AM
03/13/18 03:23 AM
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I had a set of 9second Phils pistons hard anadised in SO CA to save them, he had a bad set of solid lifters that the tops started failing allowing pieces of them to get embedded into the forged Ross pistons skirts, they where 4.080 340 pistons and he didn't want to go to the next size bigger so we saved them by doing what we had done shruggy That company was a aerospace company and they won't do them anymore whiney that company made them exactly the same size as they where new, we could of had another .0010 to .0030 added onto the diameter of the skirts for no extra costs work
On your deal I wouldn't hesitate a second to look at some of the current coatings out there now to save them scope up
Don't take a chance on doing anything not proven, it ain't worth it to take a chance on any Hi Po motor parts tsk

Last edited by Cab_Burge; 03/13/18 03:25 AM.

Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: turning piston diameter down [Re: rowin4] #2465630
03/13/18 03:47 AM
03/13/18 03:47 AM
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Finish on piston has a lot to do with how they run also. We were shocked on our hi reving 2 strokes engines what a difference finer or coarser finish would do on power. We would make one in the cnc lathe and dyno an engine. Depending what the power was like we would change it and try again. We tried different finish on the turning getting better and also getting worse on our results. Once we found what we like we ran all of our pistons this way. That is one advantage of having everything in house.

Re: turning piston diameter down [Re: rowin4] #2465633
03/13/18 04:33 AM
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Another thing to keep in mind is that the two different alloys will look a lot different on the skirts, the tight alloy look a lot worse after use than the looser alloys do with the same abuse work
My message is to measure them to see if there hurt or not scope
Don't always trust your eyeballs when it comes to judging race parts tsk Check them out thoroughly first before making any decisions on race parts, just like you should on women whistling grin whistling


Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: turning piston diameter down [Re: rowin4] #2465664
03/13/18 10:20 AM
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Originally Posted By rowin4
A friend of mine has a set of JE gas ported pistons that are .060 0ver .They have lite scratches on the skirts. He's going to toss them. Could they be turned down to a .030 over size? and if so at what cost.


Got a pic of the worst one?

Re: turning piston diameter down [Re: LSP] #2465929
03/13/18 06:43 PM
03/13/18 06:43 PM
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Romeo MI
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Originally Posted By LSP
Originally Posted By rowin4
A friend of mine has a set of JE gas ported pistons that are .060 0ver .They have lite scratches on the skirts. He's going to toss them. Could they be turned down to a .030 over size? and if so at what cost.


Got a pic of the worst one?


If they are just lightly scuffed I'd use them..
I have used some fairly ruff ones.. just use
a stone on them.. you will be surprised.. I have
had 1 set coated and they are still working well
on a street engine
wave

Re: turning piston diameter down [Re: rowin4] #2465949
03/13/18 07:10 PM
03/13/18 07:10 PM
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If the skirts are the only thing wrong why not just get the skirts coated???

Re: turning piston diameter down [Re: rowin4] #2466021
03/13/18 09:02 PM
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gulfport, ms, west mi
rowin4 Offline OP
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How much does the coating add in thickness?


it's ok to butt heads, just don't do it with a butthead
Re: turning piston diameter down [Re: rowin4] #2466023
03/13/18 09:08 PM
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Romeo MI
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Originally Posted By rowin4
How much does the coating add in thickness?


I had .004 added to a set.. they can add more
wave

Re: turning piston diameter down [Re: rowin4] #2466087
03/13/18 11:02 PM
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I would say all if not all NASCAR engine builders turn their own pistons.

Re: turning piston diameter down [Re: rowin4] #2466172
03/14/18 01:35 AM
03/14/18 01:35 AM
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I talked to a engine builder and had him look at them, he said he'd run them as is . This of coarse changed my game plan of getting a free set of $800. pistons as the owner of them was there also. Now he's peed as he bough a new set on advice of another builder.


it's ok to butt heads, just don't do it with a butthead
Re: turning piston diameter down [Re: rowin4] #2466206
03/14/18 03:02 AM
03/14/18 03:02 AM
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Originally Posted By rowin4
I talked to a engine builder and had him look at them, he said he'd run them as is . This of coarse changed my game plan of getting a free set of $800. pistons as the owner of them was there also. Now he's peed as he bough a new set on advice of another builder.


Make him a offer of a little less than 40% and
see what happens(this based on how they look)
wave

Re: turning piston diameter down [Re: cudaman1969] #2466780
03/15/18 07:04 AM
03/15/18 07:04 AM
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Originally Posted By cudaman1969
I would say all if not all NASCAR engine builders turn their own pistons.


No, the only team turning any pistons is Hendrick.

Re: turning piston diameter down [Re: rowin4] #2468415
03/19/18 12:43 AM
03/19/18 12:43 AM
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Kingman, Az
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Fellaz, what about the ring fitment. Won't the inside diameter of the ring pinch the piston inner groove?


Dakota for life!
Re: turning piston diameter down [Re: Scojodak] #2468431
03/19/18 01:42 AM
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Originally Posted By Scojodak
Fellaz, what about the ring fitment. Won't the inside diameter of the ring pinch the piston inner groove?

Only if you don't check the back clearances properly scope
I shoot for .005 minimum with the rings pushed all the way into the ring lands, 1st,2nd and 3rd rings scope wrench up
If it has more than .025 it is time for ring spacers up


Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: turning piston diameter down [Re: MR_P_BODY] #2468434
03/19/18 01:45 AM
03/19/18 01:45 AM
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rowin4 Offline OP
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Originally Posted By MR_P_BODY
Originally Posted By rowin4
I talked to a engine builder and had him look at them, he said he'd run them as is . This of coarse changed my game plan of getting a free set of $800. pistons as the owner of them was there also. Now he's peed as he bough a new set on advice of another builder.


Make him a offer of a little less than 40% and
see what happens(this based on how they look)
wave





I talked to him last Wednesday and he said after he thought about what the engine guy said about still being usable , he said he was going to keep them. I'll bring it up once in awhile as he probably won;t ever use them as his block is bored to the next oversize.


it's ok to butt heads, just don't do it with a butthead
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