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Pupsvette76 11-28-2012 06:41 PM

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

prostreet6t9 11-28-2012 06:58 PM

How tall is your tire??

Pupsvette76 11-28-2012 07:45 PM

It's a 295 50 15 =27inches tall

big gear head 11-28-2012 07:54 PM

What will you be using the car for?

AutoGear 11-29-2012 06:51 AM

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.

C-10 11-29-2012 08:03 AM

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.

prostreet6t9 11-29-2012 09:39 AM


Originally Posted by AutoGear (Post 1617013)
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.

vinniekq2 11-29-2012 10:47 AM

If you are racing then you need some tires first.The trans wont last long

prostreet6t9 11-29-2012 04:59 PM


Originally Posted by Pupsvette76 (Post 1616916)
It's a 295 50 15 =27inches tall

As Autogear stated... I'd shoot for a 331 or 355 gear.

632Mantis 11-29-2012 06:43 PM

Larger diameter rear tires ( 29" slicks )
3.73:1 gears
Powerglide tranny.


Pupsvette76 11-30-2012 02:53 PM

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

vinniekq2 11-30-2012 03:25 PM

does it run ok with that cam?

Pupsvette76 12-01-2012 05:20 PM

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

vinniekq2 12-01-2012 07:24 PM

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 many cfm does your turbo charger system move?

Pupsvette76 12-04-2012 02:54 PM

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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