402 CID ls2 vs ls3 top end
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402 CID ls2 vs ls3 top end Looking at a tsp 402 long block. Is there a big difference between the PRC As Cast 225/237 vs 255/260?
Reason for asking is I already have a MSD intake for a cathedral port head. Is it worth the hassle to sell it and buy a ls3 compatible intake for the 255/260 heads?
Will be running my current ARH 1 3/4 headers because it took a lot of welding and adjusting to get them fitted nice with V bands and catback. Don’t want to go through that again.
What all else is involved in this swap? Car is a 02 Camaro SS t56 12 bolt. Weekend car. Strip/street. Goal is 500+ rwhp and 10s at the strip.
Any info would be greatly appreciated.
Reason for asking is I already have a MSD intake for a cathedral port head. Is it worth the hassle to sell it and buy a ls3 compatible intake for the 255/260 heads?
Will be running my current ARH 1 3/4 headers because it took a lot of welding and adjusting to get them fitted nice with V bands and catback. Don’t want to go through that again.
What all else is involved in this swap? Car is a 02 Camaro SS t56 12 bolt. Weekend car. Strip/street. Goal is 500+ rwhp and 10s at the strip.
Any info would be greatly appreciated.
Last edited by 35thanni; Nov 23, 2019 at 02:59 PM.
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I am in the same situation as you and from what I have researched and discussed with a lot of the sponsors, no it wouldnt be worth it. Here are a couple formulas to determine what your engine demands for optimal performance (race car).
(Cid × rpm).000978474 / # cyl = Required CFM at peak piston velocity at peak power.
Minimum CSA = (Bore × Bore × Stroke × RPM × .00353) / 613.8
Optimal Port Volume CC = Minimum CSA × Port length × 16.387
The information you'll have to find is what is the CSA (or intake port length) of these heads you listed and what head best matches the CSA requirements of your engine?
For a 402:
Optimal CSA @ 6500 is ~2.39
Optimal CSA @ 7000 is ~2.58
(Cid × rpm).000978474 / # cyl = Required CFM at peak piston velocity at peak power.
Minimum CSA = (Bore × Bore × Stroke × RPM × .00353) / 613.8
Optimal Port Volume CC = Minimum CSA × Port length × 16.387
The information you'll have to find is what is the CSA (or intake port length) of these heads you listed and what head best matches the CSA requirements of your engine?
For a 402:
Optimal CSA @ 6500 is ~2.39
Optimal CSA @ 7000 is ~2.58
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From: Coast of San Mateo County Between Pacifica & HMB
Cathedral Heads, PRC 237, TFS 235, AFR 230, MMS 235s will all easily support 500+ RWHP and 10s for your 402"
with 11.0:1 Comp and at least 239*/245* .620"/.600" Cam.
with 11.0:1 Comp and at least 239*/245* .620"/.600" Cam.
Thread Starter
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Unfortunately, 91 octane is the best we have.
The ls3 based 418 is also an option. Would I be missing out on some power using the ls2 top end on those cubes?
Tsp also has ls7s with the ls2 top ends available too for not that much more $$.
The ls3 based 418 is also an option. Would I be missing out on some power using the ls2 top end on those cubes?
Tsp also has ls7s with the ls2 top ends available too for not that much more $$.
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Difference between a 402ci and a 418ci with the same given heads, cam ,intake , etc would be around 20-25 hp approximately. With a 418ci bigger bore the heads would have more room to work/breathe.
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but the 402 can easily meet your goals, how fast do you want to go and how much can you spend is what it comes down to.
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Just sold the msd. This makes things easier (less biased).
No specific power goal but cost vs gain is crucial.
Its hard to guage the power difference between the options because there are so many variables to each build but on average this is what I’m seeing.
402 ~ 500rwhp
418 ~ 525-550rwhp
Ls7 ~ 550-580rwhp
I know the headers will choke the bigger blocks more so those numbers may be even closer.
Also, the 402 and 418 are strokers and the Ls7 is stock displacement. Not sure if that alters power delivery and drivability at all.
No specific power goal but cost vs gain is crucial.
Its hard to guage the power difference between the options because there are so many variables to each build but on average this is what I’m seeing.
402 ~ 500rwhp
418 ~ 525-550rwhp
Ls7 ~ 550-580rwhp
I know the headers will choke the bigger blocks more so those numbers may be even closer.
Also, the 402 and 418 are strokers and the Ls7 is stock displacement. Not sure if that alters power delivery and drivability at all.