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Discussion Starter #1 (Edited)
I'm looking for a little help deciding what rear gear to change to in my Nova. The last time at the track, I was running out of RPM quite early in the 1/4 (the car was setup for the 1/8th mile before I owned it) with the current 5.29 gears.
It is mostly street driven so obviously, the 5.29's are way overkill however I still want to be able to pull great 60's at the track.

The car is tubbed with 33" Mickey's, mild 468bbc, turbo 350 trans with 3000stall.
My initial decision was to change from 5.29 to 4.56. I'm wondering how much my cruising speed will change? Currently, I'm at about 3200- 3300RPM cruising at 80km/h (~50mph). I know there are calculators out there but I'm looking for personal experiences with this size of a gear drop.

Changing to 4.86's may not be enough as I'm currently turning ~6400RPM at the top end of the track with the 5.29's and not moving any faster.

Changing to 4.33's may be too much drop as I still want it to launch like hell.

Any thoughts are appreciated. Let me know if you need more info.
Thanks!
 

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I bet with the TH350 first gear and your big block that the launch will still be good with 4.30 gears- how well does it hook up now? Street tires? footbrake?
I bet with the 5.29's you hit your 6400rpm well before the stripe?
 

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Discussion Starter #5 (Edited)
I honestly dont know the formula to figure out what you need but I can tell you the 4.86 gears in our 63 drive great on the street. I am sure somebody will come in with the formula to figure it out. What rpm would you like to trap at?
I would like to trap at 110 - 115

I bet with the TH350 first gear and your big block that the launch will still be good with 4.30 gears- how well does it hook up now? Street tires? footbrake?
I bet with the 5.29's you hit your 6400rpm well before the stripe?
Tires are 33x19.5-15 Mickey Thompson Sportsman Pro's and the hook is OK..good at the track when you really heat em.

It's been a while since i've been to the track with it but I know I run out of RPM well before the stripe.
 

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Mine with 4.10 and a 29.00 tire and T-350 floats the valves at 5800 at the 1000" mark and goes through the traps at 11.80 @ 115.
 

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I had 60 foots in the mid 1.3's with 3.73's and a 28" tire.
4.33's with the 33" tire would be somewhat close to the same ratio, but that would get you 140+ at 6400 rpm.
 

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i run a 4.30 gear with a 32" tire and turn 6100 rpm out the back. if your running a mild bbc you dont need to turn it past 6000, so i would run a 4.30 and your cruising rpm would be alot beter also. my car 60' 1.38 ish with this combo and a SBC th400. oh and i trap at 125 mph i the 1/4
 

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I'd run the 4.30's. It'll make cruising a lot more enjoyable and will still pull through the traps. Might give you room to spray it too :devil:

Kev
 

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i think ,,

I think i'd get a better converter too . That will help you get away with not as much gear and still do great 60 ft's.

I like big gears , they're just alot of fun i think. Really gets things happening quick.

A better converter might make it a great 1/8 car and 1/4 car both and happier driver on the street with the 456's .
 

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Discussion Starter #14
Thanks for the replies guys.
I'm still on the fence. 4.86's are out of the picture - that much I know.

I've not had my motor dynoed, maybe I need to roll onto the chassis dyno to get a baseline where my curve might be.

I'm kind of leaning towards 4.56's just because the 4.33's might be TOO much of a change. I was messing around with the formulas that 6nova4 posted and mathematically, the 4.33's will pull me through the traps at ~5200rpm which i would think is below the power curve.

It's not a huuge difference between the 33's to 56's - maybe i'm just being really picky now. :rolleyes:
 

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Holy smoke Batman. 5:29 and 4:86's with a t350 lol. I guess your idea of streetable cruising (highway included) is different than mine.
 

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Discussion Starter #16
Holy smoke Batman. 5:29 and 4:86's with a t350 lol. I guess your idea of streetable cruising (highway included) is different than mine.
With a tall tire it isn't as bad as it sounds. I bought the car with the 5.29's already in there and i'm now looking for a change.
 
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