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Piston to Wall Clearance for 2355 "Six Pack" pistons??
#1371315
01/17/13 05:32 PM
01/17/13 05:32 PM
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Joined: Nov 2012
Posts: 264
Farmington Hills, MI
BPBP440
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I know alot of you are running these pistons in street applications like mine. Anyone have info on what these particular pistons should be installed at for clearance? While trying to choose a piston for my 440 .040 over, I called the Speed Pro's techline to see what the typical range of undersize is on the 2355 pistons and what wall clearance is recommended. I was told they are provided approx .0015 under specified bore size. Wall clearance however was difficult to get out of him, since "it would be a liability" if he gave a number and then something went wrong with the engine  . Eventually he came out with the info that .0015 - .0025 would be appropriate for a street driven car. This sounds tight to me, more like Hyper pistons clearances, not forged. Thanks!
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Re: Piston to Wall Clearance for 2355 "Six Pack" pistons??
[Re: hemiiroc]
#1371319
01/18/13 12:44 AM
01/18/13 12:44 AM
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Joined: May 2007
Posts: 1,445
Maryland
Dads426
pro stock
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Maryland
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I believe the newer pistons (from Speed-Pro with coated skirts) can be run tighter than the older ones. I used the older TRWs in a 440 and ran them pretty tight, at the advice of Bob George (I think about 0.0025"). This may help: Moparts
2012 422 Allstars NSS Champion
2013 422 Allstars NSS Champion
2014 422 Allstars NSS Champion
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Re: Piston to Wall Clearance for 2355 "Six Pack" pistons??
[Re: Dads426]
#1371320
01/18/13 01:06 AM
01/18/13 01:06 AM
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Joined: Nov 2012
Posts: 264
Farmington Hills, MI
BPBP440
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The reason for my question is that I plan to only get my block honed to the PWC required, as it is already .040 over and the walls look good. However, if the 2255's really come .0015 undersize, and my walls are already between zero and .003 oversize, then the best I can achieve on some of the cylinders is .0045 PWC. If they really do need to be run tight, like .0025, then this piston is not an option for me. Or am I overlooking something? My bore measurements are attached, if interested. Thoughts welcomed.
Last edited by BPBP440; 01/18/13 01:16 AM.
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Re: Piston to Wall Clearance for 2355 "Six Pack" pistons??
[Re: BPBP440]
#1371321
01/18/13 03:50 AM
01/18/13 03:50 AM
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Joined: Aug 2003
Posts: 43,911
Bend,OR USA
Cab_Burge
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Bend,OR USA
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Is the average diameter, a+b divided by 2, the amount above the bore size in thousands? Forged pistons, the new ones look like cast pistons to me but Speed Pro insists there still forged, need more clearances than the cast or hypertutics(SP?) do  I wish there was a relaible way to determine the thickness of the coatings, anyone know how to check that The last set I bought and used was a set of the 4.350 bore size, it seems to me that they measured big on the sides with the coatings, like 4.3479 to 4.3481 I guess you could try measuring them at the very bottom of the skirts where the coating is not on them 
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Piston to Wall Clearance for 2355 "Six Pack" pistons??
[Re: BPBP440]
#1371322
01/18/13 09:12 AM
01/18/13 09:12 AM
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Joined: Jan 2003
Posts: 13,543
Marion, South Carolina [><]
an8sec70cuda
I Live Here
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I Live Here
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Posts: 13,543
Marion, South Carolina [><]
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.0045" pwc w/ that piston will be fine. That's about where I'd want them on a fresh build myself. 
CHIP
'70 hemicuda, 575" Hemi, 727, Dana 60
'69 road runner, 440-6, 4 speed, Dana 60
'71 Demon 340, no drivetrain, on blocks behind the barn
'73 Chrysler New Yorker, 440, 727, 8.75
'90 Chevy 454SS Silverado, 476" BBC, TH400, 14 bolt
'06 GMC 2500HD LBZ Duramax
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Re: Piston to Wall Clearance for 2355 "Six Pack" pistons??
[Re: Cab_Burge]
#1371323
01/18/13 09:32 AM
01/18/13 09:32 AM
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Joined: Nov 2012
Posts: 264
Farmington Hills, MI
BPBP440
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Quote:
Is the average diameter, a+b divided by 2, the amount above the bore size in thousands?
That is correct. Bore gauge was set-up up to 4.360 and zero'd. So each measurement is the amount oversize/undersize from 4.360.
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Re: Piston to Wall Clearance for 2355 "Six Pack" pistons??
[Re: BPBP440]
#1371324
01/18/13 10:32 AM
01/18/13 10:32 AM
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Joined: Jan 2003
Posts: 75,326
A gulag near you.
JohnRR
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Quote:
Quote:
Is the average diameter, a+b divided by 2, the amount above the bore size in thousands?
That is correct. Bore gauge was set-up up to 4.360 and zero'd. So each measurement is the amount oversize/undersize from 4.360.
Did you do this wit ha torque plate installed ?
why not just go to diamond and get a piston , if you need it a little oversized they can do it for a small upcharge . those TRW pistons are very HEAVY
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Re: Piston to Wall Clearance for 2355 "Six Pack" pistons??
[Re: JohnRR]
#1371325
01/18/13 10:44 AM
01/18/13 10:44 AM
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Joined: Nov 2012
Posts: 264
Farmington Hills, MI
BPBP440
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Did you do this wit ha torque plate installed ?
Did I measure with torque plate installed? No I did not.
For clarification, this motor is in a car I bought recently (71 440, .040 over). The motor work had been done previously, but I still took it out and pulled it down to see what was in there (based on a low Compression test reading at 130-134PSI). Had smog pistons, came out to ~7.6:1.
So far, I have had nothing additional done to the block and these are measured values of the block as removed from vehicle.
Last edited by BPBP440; 01/18/13 01:41 PM.
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Re: Piston to Wall Clearance for 2355 "Six Pack" pistons??
[Re: JohnRR]
#1371326
01/18/13 03:37 PM
01/18/13 03:37 PM
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Joined: Nov 2012
Posts: 264
Farmington Hills, MI
BPBP440
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Quote:
why not just go to diamond and get a piston , if you need it a little oversized they can do it for a small upcharge . those TRW pistons are very HEAVY
877g +/-10g for piston and pin.
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Re: Piston to Wall Clearance for 2355 "Six Pack" pistons??
[Re: BPBP440]
#1371327
01/18/13 04:13 PM
01/18/13 04:13 PM
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Joined: Jan 2003
Posts: 75,326
A gulag near you.
JohnRR
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A gulag near you.
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Quote:
Quote:
why not just go to diamond and get a piston , if you need it a little oversized they can do it for a small upcharge . those TRW pistons are very HEAVY
877g +/-10g for piston and pin.
Which piston is that ? TRW 2355 is close to 1100 grams piston and pin.
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Re: Piston to Wall Clearance for 2355 "Six Pack" pistons??
[Re: JohnRR]
#1371328
01/18/13 04:24 PM
01/18/13 04:24 PM
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Joined: Nov 2012
Posts: 264
Farmington Hills, MI
BPBP440
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Quote:
Quote:
Quote:
why not just go to diamond and get a piston , if you need it a little oversized they can do it for a small upcharge . those TRW pistons are very HEAVY
877g +/-10g for piston and pin.
Which piston is that ? TRW 2355 is close to 1100 grams piston and pin.
That is for the Speed-Pro Forged Pistons ZL2355F40, according to the Summit Tech line.
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Re: Piston to Wall Clearance for 2355 "Six Pack" pistons??
[Re: BPBP440]
#1371329
01/18/13 07:47 PM
01/18/13 07:47 PM
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Joined: Feb 2003
Posts: 21,318
Manitoba, Canada
DaytonaTurbo
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Quote:
Quote:
Quote:
Quote:
why not just go to diamond and get a piston , if you need it a little oversized they can do it for a small upcharge . those TRW pistons are very HEAVY
877g +/-10g for piston and pin.
Which piston is that ? TRW 2355 is close to 1100 grams piston and pin.
That is for the Speed-Pro Forged Pistons ZL2355F40, according to the Summit Tech line.
The info I have says the L2355F30 weighs 872g, excluding pin. I think they made them to be close enough to par with stock pistons that you didn't have to rebalance.
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Re: Piston to Wall Clearance for 2355 "Six Pack" pistons??
[Re: viperblue72]
#1371333
01/18/13 11:13 PM
01/18/13 11:13 PM
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Joined: May 2004
Posts: 5,123
Warrenton, VA
RoadRunnerJD
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Warrenton, VA
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Quote:
They are definitely right around 875g without the pin.
I wouldn't dwell on the weight. You can find lighter pins and remove some metal under the pistons to lighten them some if you want but unless you are trying to wring that one extra tenth of a second out of it and race every weekend, the weight is not going to make that much difference. Otherwise, but lightweight pistons and rods and go all out.
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Re: Piston to Wall Clearance for 2355 "Six Pack" pistons??
[Re: RoadRunnerJD]
#1371334
01/18/13 11:24 PM
01/18/13 11:24 PM
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Joined: Nov 2012
Posts: 264
Farmington Hills, MI
BPBP440
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Quote:
Quote:
They are definitely right around 875g without the pin.
I wouldn't dwell on the weight. You can find lighter pins and remove some metal under the pistons to lighten them some if you want but unless you are trying to wring that one extra tenth of a second out of it and race every weekend, the weight is not going to make that much difference. Otherwise, but lightweight pistons and rods and go all out.
Really, this will be a street cruiser. I would like to get close to the weight of the cast Federal Mogul 424P's that were in it, so that I will not need to rebalance.
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One thing you can do is the measure the pistons, make a mark on them so you measure them in the exact same spot both times, and put one in a oven, set the temps at 250 F and then let it up warm up in the oven for a while, 15 minutes or longer and then remeasure it in the same spot and see how much it grew 
