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Author Topic:   Gearing question
Jimhobby02
Dirt Full Roller

Total posts: 69
posted April 22, 2002 09:43 PM
How bad off would I be running a 6.02 final drive on a med to high bank 1/3 and 3/8?

ryan
Dirt Freak

Total posts: 430
posted April 23, 2002 12:48 AM
I cant tell you how close that gear because I have never raced that size of track, but to help you out better the other guys will need to know the roll out of your tire and how many RPM's you want to turn. I run a 6.88 on a 3/10th mile and turn 5500

Jimhobby02
Dirt Full Roller

Total posts: 69
posted April 23, 2002 05:19 AM
I guess I am not sure how many RPMS I want to turn. I am fairly new at this. I run P205-75-R15 radial tires. I am looking for a gear ratio that is easier to manage thru the turns. If it helps any I am using a power glide with a 1.76 low gear and a torque converter.

[This message has been edited by Jimhobby02 (edited April 23, 2002).]

RangeRover
Dirt Maniac

Total posts: 174
posted April 23, 2002 08:22 AM
You should be pretty good. On a 3/8 track, that gear is a great compromise between good exit power and too much RPM. With 84" to 88" tire circumference, you will see between 6400 and about 5900 RPM. If you can tune your engine to make torque around there and tune final drive with tire size to suit conditions, you'll be OK.

racer17j
Dirt Forum Champ
Total posts: 1565
posted April 24, 2002 03:33 AM UIN: 54865418
i'm asuming that your are running imca hobby right ? if so most of the guys around here are running 6.33 on 3/8 and a 650 on 1/3's with those tires that gear you have now might work alright on a 1/2 thats what we all run but if your running a 3/8 with it you'll only turn about 58-6000. what are the specs for your cam so we can help you find out what your power band and rpm you should run is ?

[This message has been edited by racer17j (edited April 24, 2002).]

Jimhobby02
Dirt Full Roller

Total posts: 69
posted April 24, 2002 06:34 AM
Yes, I run IMCA hobbystock. My cam is from speedway and is designed(according to the catalog) to run from 3000-6500. It is a Hydraulic cam with gross valve lift of .480 and .494

racer17j
Dirt Forum Champ
Total posts: 1565
posted April 24, 2002 01:52 PM UIN: 54865418
so 6500 max you would't want to run that 6.02 on either track if you have a ford rear end i would get a 6.33 and a 6.50 but if your running a gm go with a 3.55 and a 373 with low gear or you could go down to 205 70 14 tires that might help a little with your 6.02 but i would go with the gear since you can't change tires sizes without doing all 4

Flatlander
Dirt Freak

Total posts: 310
posted April 24, 2002 10:25 PM
like 17J says not enough gear you need a 640-656 on a 3/8 a 630 or 640 on the 1/3 and the 1/2 I really would try diff. ones

RangeRover
Dirt Maniac

Total posts: 174
posted April 25, 2002 08:23 AM
Dang, those type of gear ratios around here would disassemble one's valvetrain at the end of the straight. The important thing is that your valvetrain and engine are designed and prepared to live at the rpm that you want to run. I've also seen where someone's large 3/8 track is almost identical to another's small 1/2 mile track, so keep that in mind.

ryan
Dirt Freak

Total posts: 430
posted April 25, 2002 11:46 AM
Try the gear you have and see how it works if anything its going to be a little low so see how you like it before you make any changes

Flatlander
Dirt Freak

Total posts: 310
posted April 25, 2002 12:03 PM
you're right track design does have a part in gearing we run mostly high banked tracks I personally run a688 on 1/4 a656 on 3/8 and a and some 1/3 buthigher on others do turn a lot of rpms anywhere from 6300 to 7200

Eljojo
Dirt Freak

Total posts: 273
posted April 25, 2002 07:59 PM
Something that I've been fooling around with is what I call "mile per hour" I used to really twist sbc's up (over 7 grand) but lately I've tried running in the low 6's. You'll have to degree your cam in around 99-100 to really make the low end torque. By the end of the straight you'll run out of power--but I think that I'm as fast as any car on the track. We've got "stock" rules on the heads (humps) flat pistons, intakes are limited to Bowtie Marine or Edelbroc
Performer with header tubes restricted to 1 5/8. That, to me, even with a decent 4 bbl, cuts down on the amount of "flow" thru the motor. I believe that by keeping the power band down into a decent rpm range I may be actually making more speed. I'm also hoping that the motor will last..there's better stuff on the market than I've got in the motor---but I built what I could (or thought I could) afford.
Gearing is, to me, just another link in the chain. To optimise the car and driver's ability--everything has got to work together! AND, along those lines...the car is a whole lot easier to control exiting the turns.

jlfastride
Dirt Maniac

Total posts: 104
posted April 28, 2002 11:19 PM
power is the key to gearing i ran 2 diff motors on the same track in the same car 1 was a f/t 355 with solid cam and stock heads and the other was a 12.5 to 1 406 with roller and sportsman heads both with same carb and 2 barrel intake had to use 6.20 gear with 355 and 5.14 with 406 same rpm range competetive with both i realize that this is extreme but i beleive you will experience something similar on a smaller scale.

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