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LS3 Forged Piston Sizing
Thread Starter
Safety Car
Joined: Apr 2007
Posts: 3,582
Likes: 137
From: SoCal CA
LS3 Forged Piston Sizing
Hey guys, im about to pull my motor and install forged pistons and rods in it (LS3). I just wanted to make sure I was right, the stock bore is 4.065, so if I have the cylinder cleaned up 0.005 to 4.070 I should find a piston for a 4.07 bore correct? I know it sounds obvious but I want to be sure im on the right track. Also I heard forged pistons can expand more so I wasnt 100% sure. Going with Diamond forged pistons 4.07 borefor 3.622 stroke with a -12.3 dish and Scat 4340 forged H beam rods with ARP 2000 bolts. Going in my vortech blown LS3 C5, 600rwhp on 8psi.
Pro
Joined: Nov 2007
Posts: 661
Likes: 2
In most cases yes. If you order a 4.070 piston that will be it's nominal size. Meaning there is some sort of piston to wall clearance built into it (IE the piston will measure out at 4.068). Typically for FI applications it's not enough and you will need to do additional honing to get the P2W where you want it. That's why you don't do a final bore/hone on the engine until you have the piston set in your hand so they can each be measured and matched to the correct hole.
I will say you will want to check with each manufacturer or vendor though because you may order a 4.070 piston and get a piston set that measures out at 4.070 in which case you would have to hone out the additional couple thousandths to get your desired P2W.
I will say you will want to check with each manufacturer or vendor though because you may order a 4.070 piston and get a piston set that measures out at 4.070 in which case you would have to hone out the additional couple thousandths to get your desired P2W.
Le Mans Master
Joined: Dec 2005
Posts: 6,999
Likes: 1,685
From: Southeast TX
Why not let your machine shop handle ordering the pistons after examining the block? More than likely your block will clean up with a .005 overbore. It is possible that it won't. The machine shop may be comfortable ordering pistons without looking at the block. I'd keep them in the loop though.
Thread Starter
Safety Car
Joined: Apr 2007
Posts: 3,582
Likes: 137
From: SoCal CA
Thanks guys. The plans we have so far are to clean up the bores to have a 0.003 piston to wall clearance with a 4.070 piston. The Diamond pistons I want are 2618 alloy which should take the abuse better then 4340. We'll wait of course to have the motor out and see what we got first. Also looking for opinions on the rings, I can order them with Ackerly & Childs high tension ductile/napier rings. Let me know what you guys think about these parts I'm looking at.
Pistons
https://texas-speed.com/p-1086-diamo...22-stroke.aspx
Rods
https://texas-speed.com/p-450-scat-h...000-bolts.aspx
Pistons
https://texas-speed.com/p-1086-diamo...22-stroke.aspx
Rods
https://texas-speed.com/p-450-scat-h...000-bolts.aspx
Le Mans Master
Joined: Dec 2005
Posts: 6,999
Likes: 1,685
From: Southeast TX
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Thread Starter
Safety Car
Joined: Apr 2007
Posts: 3,582
Likes: 137
From: SoCal CA
Thread Starter
Safety Car
Joined: Apr 2007
Posts: 3,582
Likes: 137
From: SoCal CA
Been doing my research and it looks like you dont want to exceed a 0.03 hone on a LS3 and especially for a FI setup. So Im hoping I can get away with a cleanup hone. Example, 4.065 stock bore, clean up to 4.07, size wiseco 2618 alloy piston to 4.030 to maintain recommended 0.04 piston to wall clearance.
And I think im going with Wiseco. More for the money. Better piston design, coating and rings for less $
And I think im going with Wiseco. More for the money. Better piston design, coating and rings for less $
Pro
Joined: Nov 2007
Posts: 661
Likes: 2
Been doing my research and it looks like you dont want to exceed a 0.03 hone on a LS3 and especially for a FI setup. So Im hoping I can get away with a cleanup hone. Example, 4.065 stock bore, clean up to 4.07, size wiseco 2618 alloy piston to 4.030 to maintain recommended 0.04 piston to wall clearance.
And I think im going with Wiseco. More for the money. Better piston design, coating and rings for less $
And I think im going with Wiseco. More for the money. Better piston design, coating and rings for less $
on the piston choice...may want to rethink the size a little .040 P2W is about 10 times what you want.
Last edited by narfdanarf; Oct 8, 2013 at 07:14 PM.
Melting Slicks
Joined: Apr 2007
Posts: 2,987
Likes: 16
From: Phoenix
Get the tool steel wrist pins when you order the Wiseco pistons. Only a little extra and they are much stronger. I've thought about putting forged rods and pistons in my LS3 also. When I add everything up it will be quicker and easier to just order a built short bock. Then sell my running LS3 stock shortblock.
Last edited by jon6.0; Oct 9, 2013 at 03:41 PM.