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402 LS2 10.5 Compression

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Old Jul 30, 2015 | 02:59 AM
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Default 402 LS2 10.5 Compression
I should have asked this question before I bought the engine but I wanted to get some opinions here...this is what i'm working with


-Texas Speed & Performance Custom Built Forged 402 CID
-Wiseco Forged Piston Set: 4.005' Bore, 4.000' Stroke, 6.125' Rod Length, -3cc Flat-Top, 1.110' CH, Wrist Pins & Steel Top/Napier 2nd Ring Set Included NoPRings
-PRC LS3 260CC CNC Cylinder Head
-Camshaft 242/250 .624/.624 112 LSA


Was hoping for 520whp though a 9" so I was just wanted to hear what you guys have to say here. Really wishing I had a higher compression ratio right about now...
Last edited by That_Z28_Camaro; Jul 31, 2015 at 12:47 AM.
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Old Jul 30, 2015 | 03:35 AM
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With your setup, all you need for higher compression all you need to do is mill the heads. Tighten up the chambers, check PTV and let it eat.
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Old Jul 30, 2015 | 09:04 AM
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What is the combustion chamber size? What is the deck height? Did TSP assemble the entire motor and tell you it's at 10.5:1?
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Old Jul 30, 2015 | 02:33 PM
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Called TSP and the chambers are 68cc. Furthermore he told me the compression would be at 11.2
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Old Jul 30, 2015 | 03:32 PM
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11.2 with the 68cc?
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Old Jul 30, 2015 | 03:50 PM
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Originally Posted by That_Z28_Camaro
-Wiseco Forged Piston Set: 4.005' Bore, 4.000' Stroke, 6.125' Rod Length, -3cc Flat-Top, 1.110' CH
Originally Posted by That_Z28_Camaro
Called TSP and the chambers are 68cc. Furthermore he told me the compression would be at 11.2
Do you know the deck height? If they did not mill the block, the pistons will be down the hole .005" with that compression height.

Piston .005" down the hole = 10.95:1 compression (factory 9.240" deck height)
Piston .000 deck height = 11.08:1 compression (block deck milled .005" to 9.235")
Piston .005 out of the deck = 11.21:1 compression (block deck milled .010" to 9.230")
Last edited by speedtigger; Jul 30, 2015 at 03:58 PM.
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Old Jul 30, 2015 | 04:29 PM
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There was no milling involved that I know of. I forget if it was 11.1 or 11.2 to be exact but I think he said 11.2. I'll just run this the way it is right now and see how it performs. Appreciate the help guys
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Old Jul 30, 2015 | 04:35 PM
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I'd have to look at your specific build but pretty much every block that leaves gets decked to insure straightness. The 1.110 compression height is for a 9.235 deck height and I'm pretty positive the block was decked to 9.235. I've found that most motors are .003-.005 out of the hole.
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Old Jul 30, 2015 | 08:28 PM
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for comparison I have an LS2 based 402 approx 11.5:1 TSP CNC cathedral 243s and comp 235/242 620/593 111+3. Thru a 6 speed, moser 12 bolt w 4.10s it made 537.
Scott
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Old Jul 31, 2015 | 12:23 AM
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Originally Posted by Sales2@Texas-speed
I'd have to look at your specific build but pretty much every block that leaves gets decked to insure straightness. The 1.110 compression height is for a 9.235 deck height and I'm pretty positive the block was decked to 9.235. I've found that most motors are .003-.005 out of the hole.
Thanks for the clarification and the build sheet as well


Originally Posted by SS69LS1
for comparison I have an LS2 based 402 approx 11.5:1 TSP CNC cathedral 243s and comp 235/242 620/593 111+3. Thru a 6 speed, moser 12 bolt w 4.10s it made 537.
Scott
Awesome! That's reassuring so I shouldn't be that far off
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