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Old 07-17-2008, 10:39 AM
red65mustang red65mustang is offline
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start a new thread????....
title it something like "how to build a mega TQ 451 mopar street beast motor for my Dakota"....
I have never built your particular motor....
there are lots of (mopar experienced) members better qualified to help you pick a combo....

more general food for thought:

the very general rules "key" for getting the max TQ possible at the lowest rpms possible is getting max A/F velocity possible at slow piston speeds (low rpms)....

that's what the 4x4 and RV cams are all about (excellent A/F mix quality and chamber fill to make best power possible at low rpms)...
what I don't know at all is how your heads are biased for intake versus exhaust ratio which you need to consider when selecting a cam...

and using a intake with relatively small runners (like a performer) and a wee bit small cfm rated carb to help keep up the velocity does help ....
(trivia, 383 roadrunners only had about a 450cfm carb to help make TQ)

deeper gears does make a world of difference for TQ "wow" factor....
450ft-lbs x 3.55 gears = 1597 ft-lbs
450ft-lbs x 4.56 gears = 2052 ft-lbs twisting the hides=25% more acceleration force
but try to be sensible for how deep the ratio is versus how you use the truck!
your truck is heavy so deeper is better but 3.55=roughly 3,000rpms at 70mph and 4.56=4,000(? calculator not handy) at 70mph
I'd leave the 3.55's in it and gut every last extra once of weight possible out of the truck, (performance results are the same)
4000lb truck/1597ft-lbs 3.55 gears=2.5lbs of weight per ft-lb of TQ force
5000lb truck/2052ft-lbs 4.56 gears=2.5lbs of weight per ft-lb of force
(trivia: 98%? of all of the muscle cars had deep gears standard and that's why they were a blast to drive...big cubes TQ and low gears..)

build it with about a 9.3CR so you can use 87octane and full best timing for the cam (450cubes+4,000lbs="not great"mpg)
more compression does add some to the HP "at" the HP rpms peak but adds very very little at street rpms and smaller cams don't need it

drive safe, have fun
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