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Old Nov 26, 2018 | 10:19 PM
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Default 370 build compression question

So I知 new to the LS stuff but I知 starting my 370 build and having trouble figuring the pistons to run with the 317 heads. What is a decent compression ratio to run on 93 octane fuel?
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Old Nov 27, 2018 | 08:06 AM
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Originally Posted by Trickflow1987
So I知 new to the LS stuff but I知 starting my 370 build and having trouble figuring the pistons to run with the 317 heads. What is a decent compression ratio to run on 93 octane fuel?
11.5:1 is usually pretty safe for a naturally aspirated combo with a good tune.
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Old Nov 27, 2018 | 09:11 AM
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Originally Posted by Trickflow1987
So I知 new to the LS stuff but I知 starting my 370 build and having trouble figuring the pistons to run with the 317 heads. What is a decent compression ratio to run on 93 octane fuel?
Why not run a smaller chamber head or have those milled?
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Old Nov 27, 2018 | 09:11 AM
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im at 12.3:1 on 93. and mt tunet had Zero issues making it work. Just low timing. The setup was specd for e85.
If I were to build it again for 93 oct I would shoot for around 11.5:1 . so I could keep the timing in the upper 20's

-Mavn
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Old Nov 27, 2018 | 09:30 AM
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These might help bump the compression up if using the 317 heads, valve reliefs, though a little heavier. I believe the product number has changed to PTS523A3.
https://ls1tech.com/forums/generatio...u-pistons.html
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Old Nov 27, 2018 | 10:01 AM
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Originally Posted by cula8r
These might help bump the compression up if using the 317 heads, valve reliefs, though a little heavier. I believe the product number has changed to PTS523A3.
https://ls1tech.com/forums/generatio...u-pistons.html
I just ordered the 4.00 bore pistons yesterday for an LS2 I知 building. Wiseco had them for 30% off.
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Old Nov 27, 2018 | 10:07 AM
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Originally Posted by KCS


I just ordered the 4.00 bore pistons yesterday for an LS2 I知 building. Wiseco had them for 30% off.
I was considering the domed Wiseco ones but opted out because of my smaller chamber. Also took advantage of the SRP's that were 30% off yesterday.
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Old Nov 27, 2018 | 10:14 AM
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The PTS523A3 series are a slight departure from the old Pro Tru PT124 pistons. With a 71cc chamber and net .045 piston to head clearance, they pump 10.9:1...still a little on the low side. Milling the heads .020 would net you about 11.25:1 which allows for full timing with an average street cam. Also, the pistons are 4032...so not quite as strong as a full blown Wiseco, but still good. As forged valve reliefs so you can run them with about any cam. They also have a .945 pin for the press fit Gen. 3 rods and you would leave the clips out if running press fit. If you are running a Gen. 4 rods, have the small ends honed to fit and you would use the clips they come with. This is a fairly inexpensive operation at your machine shop and while they are balancing your assembly. We have them in our warehouses for immediate delivery.
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Old Nov 27, 2018 | 10:16 AM
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Originally Posted by cula8r
I was considering the domed Wiseco ones but opted out because of my smaller chamber. Also took advantage of the SRP's that were 30% off yesterday.
Nice, SRP痴 are good piston too.
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Old Nov 27, 2018 | 01:15 PM
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If I was to run this piston with a 6.125 rod with the 317 heads and a ls9 head gasket. Would my compression be around 11.5:1?
https://www.summitracing.com/parts/wis-k447x3
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Old Nov 27, 2018 | 01:30 PM
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Originally Posted by Trickflow1987
If I was to run this piston with a 6.125 rod with the 317 heads and a ls9 head gasket. Would my compression be around 11.5:1?
https://www.summitracing.com/parts/wis-k447x3
That would put you about 11.7:1 and you could mill it down just a bit to hit your target. 2.76g/cc.
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Last edited by Summitracing; Nov 27, 2018 at 01:35 PM.
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