what gear ratio to run ?

[blazer2007]

I have a 78 2 wheel blazer with 454 450 hp.cam is comp cams xe 262h ,9 3/4 -1 comp.ratio,dual plane with avenger 830 cfm carb. engine is built very well with all the rpm goodies.auto with hughes 11 in convertor and 31 in tires.I,m puting together a 9 in rearend for it but having some doubts on gear ratio to use.I was leaning towards a 4;11 or 4;30 ratio as the richmond ratio chart says I would be under 3000 rpm at 60 mph.The truck is street driven and might see the hiway once in a blue moon and only for 20 minutes.I can change the convertor to a smaller one if needs one.As most street b.b is on the torque side and not the rpm,cam runs out at 5600 rpm on the specs.Hope I covered everything and thanks

[stich626]

mid 3's

[Marv D]

What trans are you going to run??? One of the best things you can do is use a OD trans, and stuff a deep gear in it for the best of all worlds.


And what heads are you using that this 454 is going to make 450HP with that mild mild MILD cam????

[blazer2007]

Originally Posted by Marv D

What trans are you going to run??? One of the best things you can do is use a OD trans, and stuff a deep gear in it for the best of all worlds.


And what heads are you using that this 454 is going to make 450HP with that mild mild MILD cam????

I,m running a t 400.The heads are 70,s ported, polish but not the big valved model,rollers,block is decked,windage tray.Not that hard to get 1 hp per cube

[blazer2007]

450 HP from a 454 is like falling off a log. Good machine work is the start. Flat-top pistons and good rings. The heads are actually good on these motors. A decent valve job and a few hours doing a home-brew pocket-port and valve back-cut. Eddy performer Air-gap and a Holley 750 vac secondary carb or a Eddy Performer RPM and an early BB Q-jet. Run it cool, so a good aluminum water pump and a 160 t-stat. Good headers. HEI is fine with a coil and good cap etc...cam is very flexible. Look at the Performe RPM cams, the Comp X-treme cams. Stay in the mid range, lift in the .500 range, duration in the 220d range on a wider lobe center. It'll pull the rear right out fromunder your car. 454's make torque and torque makes cars fast!

[Marv D]

Surely was not trying to offend, Sounds like I touched on a nerve and DEFINATELY was not the intent. Just thinking that is a very mild cam for the cubes. If it makes it's steam in the mid low RPM say 600 pound feet at 3000rpm,, that is only 350HP,, it will have to make some massive torque to 5250 to make 450. A 262 @ 0.050 I would think would fall short of making steam high enough in the RPM band to be an honest 450 HP with that many cubes. I would think it noses over around 4800-5000, but sounds like you know the ins and outs of the BBC much better than I. Been wrong many many times before and this surely would not be the first :-) But that has nothing to do with what yuo asked.

as far as gear.....
the simple formula for rpm and combination is
rpm =
MHP x gear ratio
divided by tire diameter (in inches)
times 336

So a 4.11 gear with the 31" tires is going to be only 2000rpm at 45mph in city traffic.

out on the highway at 65 it will only be 2900 plus any losses thrpough the converter (5-8% for a real efficient tight converter)

If your sticking with a 31" tire I'd consider a 4.56 gear
It would put you at 2200 at 45, and 3200 at 65. Would take advantage of the motor a little better than a taller gear,

But again,,, just an opinion.