help with gear choice

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help with gear choice

Post  Rickyt630x on March 19th 2015, 10:48 pm

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.

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Re: help with gear choice

Post  Curt on March 19th 2015, 11:04 pm

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
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Post  gas6999 on March 20th 2015, 7:09 am

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

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Re: help with gear choice

Post  butterbean on March 20th 2015, 9:24 am

I would also use the 3.70 gear for the 1/4 mile racing
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Re: help with gear choice

Post  Rickyt630x on March 20th 2015, 12:32 pm

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?

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Re: help with gear choice

Post  Curt on March 21st 2015, 8:09 pm

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.
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Re: help with gear choice

Post  butterbean on March 21st 2015, 11:55 pm

if he is running a 28" tire it will be close
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Re: help with gear choice

Post  Curt on March 22nd 2015, 7:10 pm

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.
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Re: help with gear choice

Post  FalconEh on March 22nd 2015, 9:18 pm

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
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Re: help with gear choice

Post  gmsmkr on March 22nd 2015, 9:36 pm

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

Post  butterbean on March 22nd 2015, 9:42 pm

moved


Last edited by butterbean on March 22nd 2015, 9:44 pm; edited 1 time in total (Reason for editing : moved)
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Re: help with gear choice

Post  butterbean on March 22nd 2015, 9:44 pm

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
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Re: help with gear choice

Post  Rickyt630x on March 24th 2015, 4:53 pm

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.

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