piston sizing issue
#2817803
09/06/20 01:00 PM
09/06/20 01:00 PM
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Joined: Oct 2003
Posts: 4,006 South Park, Pa.
68LAR
OP
master
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OP
master
Joined: Oct 2003
Posts: 4,006
South Park, Pa.
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Working with a RB .030" over. Here's my dilemma. The block has just been bored to 4.35"to fit a set of used pistons. It seems one of the pistons may be bad. I can't find pistons to fit the block. All .030" pistons are 4.35" in diameter. I need pistons with a skirt of 4.3444". Does anyone know where or who has something like this? I don't want to send the block to the machine shop. The pistons that are in there now are older Pro Tru's
4 speed street legal. Best time 10.99 @ 124 mph on 93 octane pump gas @ 3926# total weight
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Re: piston sizing issue
[Re: Cab_Burge]
#2817824
09/06/20 01:52 PM
09/06/20 01:52 PM
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Joined: Feb 2015
Posts: 2,070 CA
crackedback
top fuel
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top fuel
Joined: Feb 2015
Posts: 2,070
CA
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Hone the cylinder to fit if they are too big and you have to use what you have. Using some used parts, got to measure everything first as I've BTDT with the orphan part or sizing different than expected. Even had new parts come in that were odd sizings among the batch.
Last edited by crackedback; 09/06/20 01:54 PM.
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Re: piston sizing issue
[Re: Cab_Burge]
#2818428
09/08/20 08:39 AM
09/08/20 08:39 AM
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Joined: Jan 2003
Posts: 13,345 Marion, South Carolina [><]
an8sec70cuda
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 13,345
Marion, South Carolina [><]
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Every brand I know of make the pistons under size to fit the over size bore, you have a bad set if they aren't smaller on the skirts than the 4.350 bore size Send them back and get the correct size Maybe they where made for a 4.355 bore size A .030" over piston for 4.350" bore size should be 4.345" or smaller if it's a forged slug. Most will want at least .005" wall clearance. The clearance is "built in." If they are really 4.350", then they aren't for a .030" over 440.
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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Re: piston sizing issue
[Re: 68LAR]
#2818567
09/08/20 02:18 PM
09/08/20 02:18 PM
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Joined: Jan 2003
Posts: 17,836 S.E. Michigan
ZIPPY
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 17,836
S.E. Michigan
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Yes. As stated above the clearance is generally built into the piston.
Shelf .030 over 440 pistons would be more accurately described as "for use in a 4.350 bore" and will measure smaller than 4.350.
Lets say .005 clearance was specified....then the piston should measure 4.345 at the prescribed measuring point. The measurement point is usually described in context with the wrist pin location and can vary somewhat.
Rich H.
Esse Quam Videri
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Re: piston sizing issue
[Re: ZIPPY]
#2818649
09/08/20 05:06 PM
09/08/20 05:06 PM
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Joined: Oct 2003
Posts: 4,006 South Park, Pa.
68LAR
OP
master
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OP
master
Joined: Oct 2003
Posts: 4,006
South Park, Pa.
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Thanks everyone. I got it rectified. Called the manufacturer and had him measure a piston from his stock. It measures 4.345. I had him ship that piston directly to me. The other piston must have been boxed wrong?
4 speed street legal. Best time 10.99 @ 124 mph on 93 octane pump gas @ 3926# total weight
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Re: piston sizing issue
[Re: 68LAR]
#2818696
09/08/20 07:02 PM
09/08/20 07:02 PM
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Joined: Jun 2012
Posts: 1,899 MYRTLE BEACH SOUTH CAROLINA
ek3
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top fuel
Joined: Jun 2012
Posts: 1,899
MYRTLE BEACH SOUTH CAROLINA
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Thanks everyone. I got it rectified. Called the manufacturer and had him measure a piston from his stock. It measures 4.345. I had him ship that piston directly to me. The other piston must have been boxed wrong?
just goes to show --- always double check everything !!
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