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Old 11-07-2008, 08:37 AM
red65mustang red65mustang is offline
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the much shorter height oem tires (27"?) are a just barely ok acceleration force match to the stock 3.50 gears...
the 33" tall tires reduces that 3.50 ratio torque multiplication factor to something around 3.00 or less...
plus they work as a lot of added rotational resistance against the motor due to they are heavy....

simple first demo for what a rear gear change does:
reverse gear is just a bit lower ratio than first gear...
floor the truck in reverse and see how quick it gets to the 4400rpms HP peak...versus how long in the taller first gear to reach 4400...
simple demo for the tires diameter and weight, borrow some 24" tall 60 series tires/wheels and test drive...

if you want to mess around for not many bucks and do something that does give results that you will likely feel (atleast a little bit):
replace the timing chain (it's shot!) and put a decent quality rebuilt dist in it (it's shot) and play with the timing curve to better match the wrong gears/tires combo....
you can gain (back) 10HP/20TQ+ over the "whole" rpm range because the spark is delivered when it's supposed to be to make max "power" cylinder pressure ATDC ...
you can add another 10HP/20TQ by tweeking the timing based on the "sweet spot" your motor wants to live at....
factory base timing is a compromise setting, so the car can work anywhere in the world (climate/altitude/etc), almost every motor made responds to from 2* up to 4* more base timing to make more Hg sooner......

my honest opinion, just adding headers to your HEAVY truck and BIG tires will make next to no performance change you can actually feel....
check the cam and heads spec's for the specific motor you are taking the headers off first,,,
if it's not a exact match to your cam and heads those tube headers may well cost you more TQ acceleration force than the added HP is worth....
truck motors are a purpose built design to make the max TQ per rpms possible to accelerate a heavy weight.....
by very carefully controlling the air flow velocity for best possible cylinder fill and A/F mix "atomization" quality when the piston speed is too slow, at less than the TQ peak rpms.....
the stock exhaust and cam and heads set up is part of the total flow equation....

footnote:
LOL! I am so so so happy my son is done with 4X4 trucks!!!
here's his last toy....
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Last edited by red65mustang; 11-07-2008 at 08:47 AM.
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