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Author Topic:   Final drive ratio
nascar_krazy
Dirt Roller

Total posts: 6
posted January 25, 2004 04:32 PM  
I'm going to race on a new to me track this year. It's a 3/8 mile flat with very tight turns. My question is what would be a good final drive ratio to start with? The car is a '78 monte with a bone stock 350 with a Blazer 284-2h cam. Tire rule is 225/70r15. I'm running a turbo 350 tranny in first. My thinking is about 8.00 is where I should be. Any thoughts?

racer17j
Dirt Forum Champ
Total posts: 5390
posted January 25, 2004 06:07 PM  
Hey 17, That's what I thought, 8.00 is too high. I have a comp program called GearCalc which I down loaded from www.racingdownloads.com I plugged in all my info and it came up with an est. rpm of 6300@60mph. I don't think that we will be going any quicker than that. So what do you think? I have a set of 2.73 for the car and if I still use 1st the final is 6.88 with a rpm of 5064@ 60mph.

racer17j
Dirt Forum Champ
Total posts: 5390
posted January 25, 2004 10:26 PM  
last year i ran my tubo 350 in second gear, with 4.11 rear gear. i don't remember my tire rollout. i was turning around 5700 rpm on my recall tach. track was small 3/8 mile.also had a blazer cam.....don't remember cam specks.

nascar_krazy
Dirt Roller

Total posts: 6
posted January 26, 2004 06:48 AM  
The bottom end is STOCK no special rod bolts, the only extra in the engine is better then stock valve springs. What do think about 2.56 rear in first? That gives me a 6.45 final. The last thing I want is to scatter engine pieces all over the track. But I also don't want to be a stone off the corners.

racer17j
Dirt Forum Champ
Total posts: 5390
posted January 26, 2004 05:22 PM  
17j,
stock valve springs, and one ugly old holley carb off of my pickup truck. very tame combo.

Econo61
Dirt Newbie

Total posts: 3
posted January 31, 2004 02:01 PM  
No matter what gears you run you want a final around 6.00

I found running a Turbo 350 with 2.73 to high of
a final. Try 3.73 gears


dan ferry
Dirt Maniac

Total posts: 183
posted January 31, 2004 04:27 PM  
besides all the other restrictions the cams not gonna let you turn high rpm anyway and for the holley off your truck what cfm is it a carb too big will help u be a stone off the corners and u already decided against that!! what heads do u have, if u can sloap the good 305 heads on if u dont have ones better theyll help low end and compression

Speed Racer X
Dirt Maniac

Total posts: 115
posted February 01, 2004 07:17 PM  
2 seasons ago we ran a Turbo 350 in 2nd with a 4.10 rear gear on a fast 3/8 track with 83" roll-out on the tires. 6500 to 6800 every week-end.

racer17j
Dirt Forum Champ
Total posts: 5390
posted February 01, 2004 09:25 PM  
2.73 with 350 turbo run that for years in low gear 3/8 banked rpm 5800-6000
lol

racer17j
Dirt Forum Champ
Total posts: 5390
posted February 05, 2004 06:00 PM  
you probably had the same prob me and ohio had not enough valve spring to let her run that hard most guys around here run that 2.73 in first on realy small 1/4's

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