Having hard time finding pistons
Thread Starter
Teching In
Joined: Jun 2013
Posts: 21
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From: Finland
Having hard time finding pistons I tore down a 370cc LS1 from which I thought I'd use internals to a new (used) 5.3 iron block.
I found out that pistons in the engine are no longer being manufactured, neither rings for them.
Piston specs: Bore size: 3.910”, Compression Height: 1.105”, Crown Volume: 6cc (dish), Pin Diameter: 0.927”, Rings: 1.5, 1.5, 3.0mm.
I want to use this crank (3.9" stroke) and connecting rods (6.125", 0.927" pin) with the iron block. I'm able to bore the block to any size, hopefully something between 3.800" to 3.905".
Compression ratio needed is around 9.7:1. This is boosted car and held up with these parts for 20 years...
I thought pistons will be a piece of cake but 3.800" bore with 1.105 (up to 1.115) CH together with -2 to -5 cc dish seem unavailable. The same gose with larger bores, I'm not able to find candidates.
Please guide me to a good source of pistons.
EDIT: Some more specs: I measured head chambers to be 68 cc. The reason for iron block is that two of the LS1 head stud threads were cracked (and welded and cracked again). I'm going to 1/2" studs next. 15 psi was the boost in use.
I found out that pistons in the engine are no longer being manufactured, neither rings for them.
Piston specs: Bore size: 3.910”, Compression Height: 1.105”, Crown Volume: 6cc (dish), Pin Diameter: 0.927”, Rings: 1.5, 1.5, 3.0mm.
I want to use this crank (3.9" stroke) and connecting rods (6.125", 0.927" pin) with the iron block. I'm able to bore the block to any size, hopefully something between 3.800" to 3.905".
Compression ratio needed is around 9.7:1. This is boosted car and held up with these parts for 20 years...
I thought pistons will be a piece of cake but 3.800" bore with 1.105 (up to 1.115) CH together with -2 to -5 cc dish seem unavailable. The same gose with larger bores, I'm not able to find candidates.
Please guide me to a good source of pistons.
EDIT: Some more specs: I measured head chambers to be 68 cc. The reason for iron block is that two of the LS1 head stud threads were cracked (and welded and cracked again). I'm going to 1/2" studs next. 15 psi was the boost in use.
you can always get them custom made, are you 100% certain comp height is 1.105? everything im seeing for 3.9 stroke with 6.125 rod is 1.165-1.175, how far are your current pistons down in the hole?
Thread Starter
Teching In
Joined: Jun 2013
Posts: 21
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From: Finland
Unfortunately I threw bearings to trash after diassembly and I cant put crank into the block without them. I only have std bearings and this crank is machined .020 undersize for mains. So I don't know how high the piston was compared to the block.
I'm certain of the 1.105 CH since I measured it from those pistons and I got the same info from manufacturer later.
EDIT: Compression height calculator shows aprximately the same 1.105 CH when I put this stroke, connecting rod and deck height as values.
I'm certain of the 1.105 CH since I measured it from those pistons and I got the same info from manufacturer later.
EDIT: Compression height calculator shows aprximately the same 1.105 CH when I put this stroke, connecting rod and deck height as values.
Last edited by Tappi; Jul 30, 2025 at 08:28 AM.
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Joined: Jul 2022
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From: Alaska
I'll be "That Guy" and say it:
A High mileage JUNKYARD pulled LQ4 might will be cheaper, easier and very likely LAST LONGER under boost than a bunch of aftermarket parts and a local machine-shop effort.
A High mileage JUNKYARD pulled LQ4 might will be cheaper, easier and very likely LAST LONGER under boost than a bunch of aftermarket parts and a local machine-shop effort.
Thread Starter
Teching In
Joined: Jun 2013
Posts: 21
Likes: 0
From: Finland
In this case the old engine was with all this expensive stuff, so it's easy to build a new block around them. If I didn't have those parts, I'd gone with stock stroke and have plenty of piston options.
Unfortunately I threw bearings to trash after diassembly and I cant put crank into the block without them. I only have std bearings and this crank is machined .020 undersize for mains. So I don't know how high the piston was compared to the block.
I'm certain of the 1.105 CH since I measured it from those pistons and I got the same info from manufacturer later.
EDIT: Compression height calculator shows aprximately the same 1.105 CH when I put this stroke, connecting rod and deck height as values.
I'm certain of the 1.105 CH since I measured it from those pistons and I got the same info from manufacturer later.
EDIT: Compression height calculator shows aprximately the same 1.105 CH when I put this stroke, connecting rod and deck height as values.
Thread Starter
Teching In
Joined: Jun 2013
Posts: 21
Likes: 0
From: Finland
I used 9.235" in calculator and deck clearance 0.01". I checked this again and yes, those pistons have stayed below the deck before. Not that they need to (?). I'm using 5 or 7 layer MLS gasket which will have somewhere around 0.05 thickness.
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Teching In
Joined: Jun 2013
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From: Finland
This mystery seems to be solved for now. The engine had around 8.9:1 CR instead of 9.7:1 which was supposed to be. Previous pistons were likely a human error due to false information about the stroke being 4" when in fact it was 3.9". So now I don't have to stick to that small CH anymore. This gives me more options on pistons.
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I tore down a 370cc LS1 from which I thought I'd use internals to a new (used) 5.3 iron block.
I found out that pistons in the engine are no longer being manufactured, neither rings for them.
Piston specs: Bore size: 3.910”, Compression Height: 1.105”, Crown Volume: 6cc (dish), Pin Diameter: 0.927”, Rings: 1.5, 1.5, 3.0mm.
I want to use this crank (3.9" stroke) and connecting rods (6.125", 0.927" pin) with the iron block. I'm able to bore the block to any size, hopefully something between 3.800" to 3.905".
Compression ratio needed is around 9.7:1. This is boosted car and held up with these parts for 20 years...
I thought pistons will be a piece of cake but 3.800" bore with 1.105 (up to 1.115) CH together with -2 to -5 cc dish seem unavailable. The same gose with larger bores, I'm not able to find candidates.
Please guide me to a good source of pistons.
EDIT: Some more specs: I measured head chambers to be 68 cc. The reason for iron block is that two of the LS1 head stud threads were cracked (and welded and cracked again). I'm going to 1/2" studs next. 15 psi was the boost in use.
I found out that pistons in the engine are no longer being manufactured, neither rings for them.
Piston specs: Bore size: 3.910”, Compression Height: 1.105”, Crown Volume: 6cc (dish), Pin Diameter: 0.927”, Rings: 1.5, 1.5, 3.0mm.
I want to use this crank (3.9" stroke) and connecting rods (6.125", 0.927" pin) with the iron block. I'm able to bore the block to any size, hopefully something between 3.800" to 3.905".
Compression ratio needed is around 9.7:1. This is boosted car and held up with these parts for 20 years...
I thought pistons will be a piece of cake but 3.800" bore with 1.105 (up to 1.115) CH together with -2 to -5 cc dish seem unavailable. The same gose with larger bores, I'm not able to find candidates.
Please guide me to a good source of pistons.
EDIT: Some more specs: I measured head chambers to be 68 cc. The reason for iron block is that two of the LS1 head stud threads were cracked (and welded and cracked again). I'm going to 1/2" studs next. 15 psi was the boost in use.
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Joined: Oct 2002
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From: Mefis
This mystery seems to be solved for now. The engine had around 8.9:1 CR instead of 9.7:1 which was supposed to be. Previous pistons were likely a human error due to false information about the stroke being 4" when in fact it was 3.9". So now I don't have to stick to that small CH anymore. This gives me more options on pistons.
Here’s a set at Summit with upgraded pins. You can get cheaper sets…of the same piston…but with a lesser quality pin. I’d go with the upgraded pin being a boost deal. 3.84” bore here, should fit in with what your doing…https://www.summitracing.com/parts/d...make/chevrolet