Very tempted

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L31MaxExpress

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To throw this sucker on the 383 while I have it apart changing lifters. Single plane with a 103mm TB. I have been considering 4.56s for a while too. I miss the snappy 5.13s I had in the 9.5 SF 14-bolt when I had the old 350 in the van. Honestly thinking of gearing it to make up for the low speed torque loss and letting it eat a bit. Cam and heads want to run to 6,200 rpm or more but it is currently choked by the marine intakes longer runners and vortec air hat at 5,500.

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L31MaxExpress

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Why so conservative? 5.13 gears, 103mm TB... pshhhh... why not go big or go home
Don't think I have not considered 5.13s, but I want to have somewhat of a useable 1st gear when the 6L90E goes in. 4.10s might actually be an acceptable trade off.
 

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Actually 4.10s would cover a torque loss of ~50 ft/lbs at the stall speed rather well, just crunching some basic numbers. At 3,000 rpm I do not feel a single plane would be that far down though.
 

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There's only one way to find out how good it would really be :Big Laugh:
It starts building vacuum at 3,500 rpm and is making 2.5 in/hg manifold vacuum at 5,500 rpm now. It would be about like pulling a restrictor plate off of it on the top-end. When I threw the marine flame arrestor with its built in velocity stack on top of the throttle body to protect the engine from large debris and made a quick test drive it made almost no vacuum to 6,200 rpm and felt like it gained 40 hp. I manually shifted it at 6,200 ish and it flew.

I have known the air inlet hat is a choke point for years, but never have found a great way to eliminate it. Back in the 350 days I worked around it by giving it a chemical oxidizer when I wanted power.

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