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Old 11-28-2012, 06:41 PM
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Help picking gear ratio

Hey guys I need some help picking the right hear ratio for my car it's a 70 chevy nova with a sbc 355 with afr 215 heads 75cc chamber edelbrock roller cam .539/.540 lift 234/238 duration at .050
Single plane intake manifold professional products efi a gt45 turbo at 15-20psi b&m hole shot converter 3000 rpm in a turbo 350... Any help is appreciated

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Old 11-28-2012, 06:58 PM
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How tall is your tire??
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Old 11-28-2012, 07:45 PM
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It's a 295 50 15 =27inches tall
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Old 11-28-2012, 07:54 PM
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What will you be using the car for?
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Old 11-29-2012, 06:51 AM
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Traditionally, turbo cars do not like a ton of rear gear. I would say somewhere in the range of 3.55:1 - 3.31:1.
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Old 11-29-2012, 08:03 AM
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Not trying to one-up anybody but my old single axle med. duty dump truck has one of those 2 speed rears, Eaton, get this- 6.50-8.85!.. The spicer 5 speed is 1:1 in 5th!.. Of course 11r 22.5 truck tires, but wow does she have some gear..

On topic, I like a combo for the street that gets you right at 10:1 in first gear, all in, through the tires.
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Old 11-29-2012, 09:39 AM
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Quote:
Originally Posted by AutoGear View Post
Traditionally, turbo cars do not like a ton of rear gear. I would say somewhere in the range of 3.55:1 - 3.31:1.
^^What he said!

It seems like the turbo like a little load put on it.
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Old 11-29-2012, 10:47 AM
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If you are racing then you need some tires first.The trans wont last long
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Old 11-29-2012, 04:59 PM
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Quote:
Originally Posted by Pupsvette76 View Post
It's a 295 50 15 =27inches tall
As Autogear stated... I'd shoot for a 331 or 355 gear.
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Old 11-29-2012, 06:43 PM
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Larger diameter rear tires ( 29" slicks )
3.73:1 gears
Powerglide tranny.

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Old 11-30-2012, 02:53 PM
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Currently there are 4.88 in it and I can just feel the engine running up in rpm to quick to make power... The gear I have doesn't allow much time in each gear and it pulls me out of my powerband
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Old 11-30-2012, 03:25 PM
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does it run ok with that cam?
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Old 12-01-2012, 05:20 PM
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It runs good I didn't wanna run a huge lift cam or a huge duration cuz I didn't want any piston to valve clearance issues
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Old 12-01-2012, 07:24 PM
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you have 4 degrees more duration on the exhaust side?you didnt say the LDA of the cam.If you have a turbo header with that cam? the duration is wrong way for split.
This engine should break the tires loose with 2.7 gears.how many cfm does your turbo charger system move?
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Old 12-04-2012, 02:54 PM
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I'm 23 and only been putting engines together for a few years so I'm kinda new to all the terms what is LDA? Do u mean LSA?
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