3.750 stroke crank?
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Joined: Jan 2019
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Post # 8......the small stroke is for class racing ... In the real world it's no Replacement for Displacement. You make just as much HP with less RPM involved. As my guy said 3.75 crank size is so OLD school SBC.... 383 at that... Been there done that. Same guys wish a 4 inch crank would fit without the special attention needed with a factory deck height gen 1 Chevy. It's cool to be different, yet crazy when you know Tq is Hp and larger is generally better. Most of those hi RPM Optima Challenge cars have went back to bigger. The 388 in Danny's (Pop) car was changed... Go figure. He made more with more Cubic inches and less RPM.
Originally Posted by tech@WS6store
Absolutely no reason to destroke an ls7. Building a 388 works ok for alot of boost but na not ideal.
Dont treat them like a gen0/1/2 small block.
Dont treat them like a gen0/1/2 small block.
I think the OP is limited in displacement by class rules. He could build a basically square 406-410 or destroke a LS7 to get there. Needs RPM and very broad power curve.
K1 3.9” stroke crank offset ground for 3.8” stroke and 2.00” rod journals.
Eagle 6.200” rod with 2.1” big end and spacer bearing for the 2.00” rod journals.
Wiseco 4.130” bore piston for a 4” stroke and have the machine shop cut the deck to make up the difference.
If that’s the case, heres what I would do:
K1 3.9” stroke crank offset ground for 3.8” stroke and 2.00” rod journals.
Eagle 6.200” rod with 2.1” big end and spacer bearing for the 2.00” rod journals.
Wiseco 4.130” bore piston for a 4” stroke and have the machine shop cut the deck to make up the difference.
K1 3.9” stroke crank offset ground for 3.8” stroke and 2.00” rod journals.
Eagle 6.200” rod with 2.1” big end and spacer bearing for the 2.00” rod journals.
Wiseco 4.130” bore piston for a 4” stroke and have the machine shop cut the deck to make up the difference.
Why do the above instead of just starting with a 3.75 crank? Are some of the recommendations for improved stability? Cheaper to do? it seems in principle you agree with the approach the OP is considering, but have a different way to get there?
Banned
Joined: Jan 2019
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Likes: 100
Just build a 408 LOL..... Good for 600 to 800+ main thing is compression for the later...Also cheaper.
👍
Don't go backwards with a big bore...you guys are correct, thinking about it....big bore wins but damn making a 4x vs a 427+ =😢
👍
Don't go backwards with a big bore...you guys are correct, thinking about it....big bore wins but damn making a 4x vs a 427+ =😢
Last edited by Smokey B; Feb 7, 2020 at 11:39 AM.
Please understand - I'm trying to learn, as it looks as though there are other considerations here...
Why do the above instead of just starting with a 3.75 crank? Are some of the recommendations for improved stability? Cheaper to do? it seems in principle you agree with the approach the OP is considering, but have a different way to get there?
Why do the above instead of just starting with a 3.75 crank? Are some of the recommendations for improved stability? Cheaper to do? it seems in principle you agree with the approach the OP is considering, but have a different way to get there?
If youre tryin to work the class then you should have a flexible wallet to begin with.
We have worked with a few guys to give them domed piston in xxx bore for both cid and max bore class rules and they had great luck.
You dont have to push the envelope to make the best power. In that aspect reliability is also a big deal. Saving cost and maybe only being a few points behind will pay off in the long run. Avg points mean alot more than winning 1 or 2 races and being broke down the rest or the costs eating your butt up.
Optimization of other parts would likely make as much if not more difference there
We have worked with a few guys to give them domed piston in xxx bore for both cid and max bore class rules and they had great luck.
You dont have to push the envelope to make the best power. In that aspect reliability is also a big deal. Saving cost and maybe only being a few points behind will pay off in the long run. Avg points mean alot more than winning 1 or 2 races and being broke down the rest or the costs eating your butt up.
Optimization of other parts would likely make as much if not more difference there
