440 bore measurements - can I run standard sized pistons?
#2928609
05/30/21 07:06 PM
05/30/21 07:06 PM
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Joined: Jan 2003
Posts: 12,043 State of Confusion
hp383
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Gentlemen, I had a machinist buddy stop over today and help me measure the bores on my 440 block.
From what I can tell I think I will be good to go with the old TRW 6 pack slugs I got from my neighbor but I am not an experienced engine builder.
The following are the bore measurements we took just below the deck at ring height. (The botom of the bores on all cylinders was 4.321")
The first number is 12 o'clock- 6 o'clock Second number is 9 o'clock - 3 o'clock
There is no discernable ridge, and crosshatch is easily visible in all holes.
And now to the numbers.
1 - 4.323 / 4.324 3 - 4.323 / 4.323 5 - 4.323 / 4.323 7 - 4.323 / 4.3225
8 - 4.323/ 4.323 6 - 4.323 / 4.322 4 - 4.322 / 4.322 2 - 4.322 / 4.3225
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Re: 440 bore measurements - can I run standard sized pistons?
[Re: hp383]
#2928744
05/31/21 01:28 AM
05/31/21 01:28 AM
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Joined: Aug 2003
Posts: 43,127 Bend,OR USA
Cab_Burge
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I Win
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Bend,OR USA
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Measure the bores at the bottom of the ring travel and the piston skirts right under the oil rings about 1/4 to 1/2 inch below and then measure the skirts (all eight pistons and bores ) at the bottom and if the skirts are smaller than below the oil rings that piston is junk, don't use it I'm thinking the pistons skirts come from the factory with the piston to cylinder wall clearances ground into them so a standard piston for the stock 4.3200 bore will have right at .0035 smaller skirts, 4.3165 , not 4.3195 or between the two Let us know what you find and decide please
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: 440 bore measurements - can I run standard sized pistons?
[Re: Moparteacher]
#2928863
05/31/21 12:24 PM
05/31/21 12:24 PM
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Joined: Jan 2003
Posts: 25,750 Rio Linda, CA
John_Kunkel
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Rio Linda, CA
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I've run a similar TRW slug with .008" with no issues. Better to hear 'em than to smell 'em.
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Re: 440 bore measurements - can I run standard sized pistons?
[Re: A727Tflite]
#2928900
05/31/21 02:20 PM
05/31/21 02:20 PM
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hp383
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Post a picture of the oil ring groove on your TRW pistons.
Does the groove have holes or slots ? I will snap a picture when I dig them out again. I have them in storage at the moment.
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Re: 440 bore measurements - can I run standard sized pistons?
[Re: Moparteacher]
#2928903
05/31/21 02:33 PM
05/31/21 02:33 PM
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hp383
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I wouldn't hesitate. Numbers look good to me. Are they optimum...probably not, but well within tolerances. Are you running nox or forced induction? If so you may need additional clearance depending on what the pistons measure. They probably measure 4.3175 or there about giving you .0045" to .0065" if your piston is machined .0025" under std. bore of 4.32.
I've run a similar TRW slug with .008" with no issues. No nitrous on this one, just a naturally aspirated M1 dual 4bbl tunnel ram setup. And either a Hughes Whiplash cam I have on hand, or possibly a Comp Thumper cam. 906 ported heads I had on my 383, Thorley tri Y headers, dual chamber mufflers. Looking for a fun street build for cruising and such. 3.73 or so gear ratio, 727 manual valvebody, something that will turn the tires, and still be able to run on the highway to get to town. May even dig out the "quiet" gear drive I bought a couple decades ago.
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Re: 440 bore measurements - can I run standard sized pistons?
[Re: hp383]
#2929392
06/02/21 08:02 AM
06/02/21 08:02 AM
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Joined: Nov 2004
Posts: 3,544 Syracuse,NY
CompWedgeEngines
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Syracuse,NY
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Not being rude, so please dont take it that way, but, if the guy that was measuring is a machinist, he should have that answer, and know how/where to measure a TRW piston I would think. Remember he clearance is in the piston, not the bore.
RIP Monte Smith
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Re: 440 bore measurements - can I run standard sized pistons?
[Re: CompWedgeEngines]
#2929508
06/02/21 02:46 PM
06/02/21 02:46 PM
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Joined: Jan 2003
Posts: 12,043 State of Confusion
hp383
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Not being rude, so please dont take it that way, but, if the guy that was measuring is a machinist, he should have that answer, and know how/where to measure a TRW piston I would think. Remember he clearance is in the piston, not the bore. Also not being rude with my reply, but being a machinist doesn't make one an experienced engine builder. So while he had the tools to take the measurements, without the experience in building engines those numbers are just numbers. We were not measuring the pistons, just the bore. My intent was to determine if the bores were still able to use a zero oversize piston. I do not have, and have not found a spec for piston to cylinder wall clearance tolerance. I came here because there are people with the knowledge to help me determine if the bores were within tolerance, or if the block was going to need to be bored for oversized pistons.
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Re: 440 bore measurements - can I run standard sized pistons?
[Re: hp383]
#2929539
06/02/21 04:34 PM
06/02/21 04:34 PM
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A727Tflite
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Not being rude, so please dont take it that way, but, if the guy that was measuring is a machinist, he should have that answer, and know how/where to measure a TRW piston I would think. Remember he clearance is in the piston, not the bore. Also not being rude with my reply, but being a machinist doesn't make one an experienced engine builder. So while he had the tools to take the measurements, without the experience in building engines those numbers are just numbers. We were not measuring the pistons, just the bore. My intent was to determine if the bores were still able to use a zero oversize piston. I do not have, and have not found a spec for piston to cylinder wall clearance tolerance. I came here because there are people with the knowledge to help me determine if the bores were within tolerance, or if the block was going to need to be bored for oversized pistons. There are two styles of forged pistons. One needs to have more piston to wall than the other. That’s why I asked for a picture or description of the oil ring groove. While we wait for that info why don’t you measure the skirts for diameter. Measure at the wrist pin height and compare to bore diameter. The street slug should work at around .002-.004 p to w. The race slugs usually run at .007 - .0075”. New pistons gain .0005 - .001” p to w after they have been run in a bit.
Last edited by Transman; 06/02/21 04:39 PM.
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Re: 440 bore measurements - can I run standard sized pistons?
[Re: hp383]
#2929735
06/03/21 11:15 AM
06/03/21 11:15 AM
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Joined: Jan 2003
Posts: 13,357 Marion, South Carolina [><]
an8sec70cuda
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I Live Here
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Marion, South Carolina [><]
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IMO std. size pistons will be just fine.
CHIP '70 hemicuda, 575" Hemi, 727, Dana 60 '69 road runner, 440-6, 18 spline 4 speed, Dana 60 '71 Demon, 340, low gear 904, 8.75 '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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