stall speed & rear gears

[markviii347]

I have built up a 302w stroked to 349 cubic inches it makes 420 hp its torque range is 1600 - 6400 rpm the transmission is a c4 built to handle up to 750 hp I a going to install this combo in my mark VIII (yes I know it wasnt made for this engine)
heres my question what converter stall speed would you suggest and what gear ratio I am retaining the stock rear axle this car will be 90% street driven
thanks for your help
markviii347

 

[JC]

RE: stall speed & rear gears

I recomend you talk to Dan at www.speedfreak.cc. He put a similar engine with a blower in an Explorer and has been driving it for a while.

 

[markviii347]

RE: stall speed & rear gears

RE: stall speed & rear gears

thank you for refering me to Dan I have sent him a email
would any of you like to take a stab at the stall speed and rear gear ratio?
I am not going to hold you to it I am just trying to find out what the popular opinion is so far I am finding that selecting a torque converter is somewhat of a black art it seems that you can have all the specs in the world and it still comes down to experience NOT a formula. and a friend of mine asked me what rpm do you want to launch at? thats the converter you pick . . I think the true answer is somewhere in between
.
what about the rear gear I dont want the engine singing all the time but I do want more performance than what the stock unit will offer I need to go into the axle anyways to install some type of posi unit may as well change the ring and pinion also
so what do ya say let me know what you think :9

 

[driller]

RE: stall speed & rear gears

RE: stall speed & rear gears

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would any of you like to take a stab at the stall speed and rear gear ratio?
[/div]

With a C4 tranny and stock tire size, I would go with 3.73 gears for power and track performance or 3.08 for best highway economy. So 3.55 would probably be best overall for a daily driver with more performance coupled with the mill you're talking.

I agree experience is the best selector for stall speeds in a torque converter. BUT having asked experienced people with the Mark VIII and the 4.6 DOHC as well as manufacturers, I would say ask a couple manufacturers for their opinion and select slightly higher IMHO as I think they tend to be slightly conservative. As a blind guess based on torque experience with the 5.0 vs. the 4.6, I would go on the high end for a typical 5.0, say 3200RPM max or lower would be my guess.