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Thoughts on new build plan ideas with fed stg 1 ls3 heads

 
Old 01-02-2019, 12:48 PM
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Default Thoughts on new build plan ideas with fed stg 1 ls3 heads

Well im 90% sure the used prc 237 heads I just bought are going back to the seller. After being disappointed on them in my other thread, they now ccd a bit less than I was shooting for. I can play with the head gasket some, but not sure I want to lose all my quench.

Considering jumping to square port after reading up on them. Plan would be the Frankenstein stg1 ls3 heads, fast 102 with medium runners, 90mm tb, 1 7/8 kooks, 238/252 114+3 620/622, 405 cubes (4.015 bore, 4 stroke), Johnson 2126 lifters, 3/8 pushrods.


With an ivc of 49.8, being a stroker motor, and the medium length runners my math is looking @6800-7000 peak.

my next bottleneck will obviously be the tb and 85mm maf, followed closely by the 2.5 ti mufflers. Depending on how bad they hold me back, Ill be looking into upgrading there as well.

Possible to still see 500tq?
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Old 01-02-2019, 03:42 PM
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Possible, but it means everything will have to be perfect. It will not be a layup
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Old 01-02-2019, 03:47 PM
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What will your compression ratio be?
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Old 01-02-2019, 03:56 PM
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Originally Posted by KCS View Post
What will your compression ratio be?
if I stay with the prc heads Ill be 12-12.2
the ls3s I can mill to whatever, but ideally 11.75ish
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Old 01-02-2019, 03:57 PM
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Originally Posted by Darth_V8r View Post
Possible, but it means everything will have to be perfect. It will not be a layup
hmmm... Id really hate to make a big $ mistake
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Old 01-02-2019, 05:00 PM
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Im calculating my dcr with the prc heads to be 8.65-8.8

thats a quench range from .044 to .038
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Old 01-02-2019, 05:11 PM
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I like your plan. Few things to consider, I would use AFR LS3 Heads out of the box with
lighter valves & appropriate springs for your set up they will out perform the OE ported
heads everywhere for your application and only need 8-12* exhaust split so
238/246- 238/250 would be ideal.

For reference I have a all Bore 396" (4.175 X 3.60" Stroke) 11.7:1
Tony Mamo MMS LS3 TFS Heads with a LLSR 243/249 (Hydraulic Roller equivalent 237/243 115+3)
adjusted for Lash. MMS Fast LS3 with Mid Length Peak @ 690 Flywheel HP Engine Dyno
from 7100-7300 & carry to 7600+ With 1 7/8 LTs. Your 4" Stroke would pull everything down
300-500 RPM roughly. Mine is for a C5 also.
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Old 01-02-2019, 05:13 PM
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OP If going with a 102 TB, why not ditch the 85mm MAF for a 100mm MAF or go Speed Density?
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Old 01-02-2019, 05:21 PM
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Originally Posted by 99 Black Bird T/A View Post
OP If going with a 102 TB, why not ditch the 85mm MAF for a 100mm MAF or go Speed Density?
my intake is a 102, but my Tb is a 90mm. Trying to reuse as many parts that came with car at the moment, but yeah if Im logging any kpa drop after Ill be upgrading
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Old 01-03-2019, 06:28 AM
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Originally Posted by 99 Black Bird T/A View Post
OP If going with a 102 TB, why not ditch the 85mm MAF for a 100mm MAF or go Speed Density?
No maf is the best flowing maf
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Old 01-03-2019, 08:26 AM
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Originally Posted by bthomas View Post

if I stay with the prc heads I’ll be 12-12.2
the ls3’s I can mill to whatever, but ideally 11.75ish
That should get you close to 500ft-lbs. The MAF might hold you back a little though but with the displacement and compression, you’re 90% of the way there.

Last edited by KCS; 01-03-2019 at 08:38 AM.
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Old 01-03-2019, 08:36 AM
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Sell MAf for $80. Buy $10 4" Tube. Go speed Density.. Profit?
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