help with gear choice

just put together a new 632bbf c-headed motor. was looking for a rear end option to asked this question but couldnt find anything so asking here.
4.600 bore
4.75 stroke.
c460 heads
I.R intake with 3 kits.
reid case 1.69 first gear glide.
running a 29.5x10.5w m/t tire.
was thinking of 3.90 gear as what i ran with small block. but might be too much? would a 3.70 gear be better choice or can/would i be ok with the 3.90 and not be out of gear with smaller tires. 1/4 car. very little 1/8mile racing would be done, probably none. best info and opinions would be helpful thanks.

What RPM do you want to cross the finish line at?  What is your convertor set up for? How heavy is the car?


Go here \/

http://wallaceracing.com/calcrgr.php

with that small of a tire I would go with a 3;70

I would also use the 3.70 gear for the 1/4 mile racing

ok thanks for the replies, i was going to buy the 3.70s but decided to ask before i go out swapping and didnt need too. like the motor to cross no more then 7500-7700. ill check out the calculator but have close or accurate is it?

Rickyt630x wrote:ok thanks for the replies, i was going to buy the 3.70s but decided to ask before i go out swapping and didnt need too. like the motor to cross no more then 7500-7700. ill check out the calculator but have close or accurate is it?

It's a close as you can get. Your convertor will tell the rest. You'll never see 7500 rpm with a 3.70 tire unless its spinning or the convertor is way down on efficiency.

if he is running a 28" tire it will be close

butterbean wrote:if he is running a 28" tire it will be close

Unless he has a locked up convertor, he'll lose 8-10% at the stripe.

Rickyt630x wrote:just put together a new 632bbf c-headed motor. was looking for a rear end option to asked this question but couldnt find anything so asking here.
4.600 bore
4.75 stroke.
c460 heads
I.R intake with 3 kits.
reid case 1.69 first gear glide.
running a 29.5x10.5w m/t tire.
was thinking of 3.90 gear as what i ran with small block. but might be too much? would a 3.70 gear be better choice or can/would i be ok with the 3.90 and not be out of gear with smaller tires. 1/4 car. very little 1/8mile racing would be done, probably none. best info and opinions would be helpful thanks.

Rickyt630x wrote:ok thanks for the replies, i was going to buy the 3.70s but decided to ask before i go out swapping and didnt need too. like the motor to cross no more then 7500-7700. ill check out the calculator but have close or accurate is it?

Curt wrote:

Rickyt630x wrote:ok thanks for the replies, i was going to buy the 3.70s but decided to ask before i go out swapping and didnt need too. like the motor to cross no more then 7500-7700. ill check out the calculator but have close or accurate is it?

It's a close as you can get. Your convertor will tell the rest.  You'll never see 7500 rpm with a 3.70 tire unless its spinning or the convertor is way down on efficiency.

If I am reading this right there is 3X kits of Mr Frosty, and that does play havoc with the calculators, RPM, and MPH numbers I think he could see 7500

632 with 3 kits and 1/4 car...... I would start with a 3.55 gear and work from there

moved

FalconEh wrote:

Rickyt630x wrote:just put together a new 632bbf c-headed motor. was looking for a rear end option to asked this question but couldnt find anything so asking here.
4.600 bore
4.75 stroke.
c460 heads
I.R intake with 3 kits.
reid case 1.69 first gear glide.
running a 29.5x10.5w m/t tire.
was thinking of 3.90 gear as what i ran with small block. but might be too much? would a 3.70 gear be better choice or can/would i be ok with the 3.90 and not be out of gear with smaller tires. 1/4 car. very little 1/8mile racing would be done, probably none. best info and opinions would be helpful thanks.

Rickyt630x wrote:ok thanks for the replies, i was going to buy the 3.70s but decided to ask before i go out swapping and didnt need too. like the motor to cross no more then 7500-7700. ill check out the calculator but have close or accurate is it?

Curt wrote:

Rickyt630x wrote:ok thanks for the replies, i was going to buy the 3.70s but decided to ask before i go out swapping and didnt need too. like the motor to cross no more then 7500-7700. ill check out the calculator but have close or accurate is it?

It's a close as you can get. Your convertor will tell the rest.  You'll never see 7500 rpm with a 3.70 tire unless its spinning or the convertor is way down on efficiency.

If I am reading this right there is 3X kits of Mr Frosty, and that does play havoc with the calculators, RPM, and MPH numbers I think he could see 7500

THANK YOU, if you are running a 800 hp engine rpm at the stripe will be different than a engine that makes 1200 hp with the same gear and converter

thanks for the replies. yes 3 scoops of Mr. Frosty on this 632. was also suggested a 3.55 gear. just not sure what i will do. maybe order both the 3.70s and 3.55 and just swap pumpkins after a few passes of testing? new converter will be order next week from Neal Chance or Ultimate Converter Concepts.