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Author Topic:   final drive
Trapper
Dirt Full Roller

Total posts: 64
posted December 30, 2003 10:17 AM  
Im running a mostly stock 2.3 ford motor on a 3/8 mile track with banking in short curves. Right now Im running dot tires 205/60/13 with a 72" runout and taching around 6800 at the end of the longest straight away when it is hooked up and getting descent traction. My rear end gear is a 3.73 and a 1.94 2nd gear in the tranny or a 7.24 final drive. I have a lot of different trannys and gears to play with and right now with the current setup im not able to catch the leaders but can keep them in sight and on the lead lap so I think im close. What final drive would you folks recommend. BTW Im running arp rod bolts and keith black hyperuetectic pistons std. bore and think the motor could do a few more RPMs but dont want to stress it too much. Thanks for any help on this one.

TRAP

b4racing
Dirt Forum Champ
Total posts: 626
posted December 30, 2003 01:43 PM  
what has been done to the head? And what cam are you running

Trapper
Dirt Full Roller

Total posts: 64
posted December 30, 2003 09:17 PM  
The head has been cut 120 thsn. and have a crane cam with .460 intake and .480 eshaust, the duration is 268. It is rated to 6500 rpm according to the spec card but I have turned it on a slick track 7500 and no valve floating noticed. BTW the valve springs are dual spring from competition matched numbers with the cam spec card with lash caps.
I hope this is enough for you to go on. If you need any more info. just let me know. I was considering just a tranny switch to a 2.14 2nd gear but not sure what to do at this point. I forgot to mention that I do have an adj. cam timing gear and have degreed the cam to spec.
thanks for any help.

TRAP

[This message has been edited by Trapper (edited December 30, 2003).]

smiley
Dirt Roller

Total posts: 25
posted December 31, 2003 09:33 AM  
go to the top of the page to menu
click on tools play with the calculaters

b4racing
Dirt Forum Champ
Total posts: 626
posted December 31, 2003 12:44 PM  
that will gain you roughly 600 rpms by switching. kind of in a rock and a hard place. It sounds like you are right there on r's. Later and good luck BObby

tay27tronnie
Dirt Full Roller

Total posts: 37
posted December 31, 2003 08:02 PM  
Hey cuz try a 2.14 trans & a 3.27 rear gear I had my tang geared at 1.94 & 3.08 and was in the same shape. I'f you think the motor will handle the R.P.M's. Hope this helps.

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dirttracker98
Dirt Freak

Total posts: 284
posted January 01, 2004 10:31 AM  
try a combo that will give you around a 7.80 & turn around 75 to 7600 rpm.

[This message has been edited by dirttracker98 (edited January 01, 2004).]

Trapper
Dirt Full Roller

Total posts: 64
posted January 01, 2004 07:28 PM  
I appreciate the input guys, Its a little frustrating trying to figure out the leaders at the track im at. Most folks are real tight lipped about their set up. Its nice to talk to fellow racers that im not racing against and get good honest input that helps a newcomer out.

I think im gonna go with a 3.55 rear gear and a 2.14 tranny and that should give me a 7.6 final drive. I hope the lower end will hold up to it. Thanks again

TRAP

b4racing
Dirt Forum Champ
Total posts: 626
posted January 01, 2004 08:28 PM  
are you running a 8" rear?

Trapper
Dirt Full Roller

Total posts: 64
posted January 02, 2004 03:20 AM  
I am running a 7.5" rear end if im not mistaking. The guy who I bought the car from threw in all the gears so I havent had to order any. The gears I got in the deal are as follows. 2.78, 3.08, 3.27, 3.55, 3.73, and a 4.10. The transmissions I have are all either 1.94 or 2.14 2nd gear.

TRAP

b4racing
Dirt Forum Champ
Total posts: 626
posted January 02, 2004 07:25 AM  
you will not have a 355 for a 7.5 you will have a 345 but if it is a 8" that has the front loader than you will have the 355. Bobby

JALD
Dirt Roller

Total posts: 18
posted January 02, 2004 08:17 AM  
Trapper, it appears that you are making a very common mistake. More RPMs does not in any way equal more power. That cam was rated at 6500 for a reason and has nothing to do with how much it can handle. The RPM range that the cam maker states on the card is what they predict will be the optimum range of power for that cam. If you think that the stated range is incorrect there are several ways of testing it. The easiest is to change nothing on the car, but your gearing and see how your times change. Possibly, the more precise way to check is to put the engine on a dyno or better yet put the car on a chassis dyno. This will give you a torque curve that you can analyze and choose what you think it your optimum RPM range.

As a side note, I am frequently told that my Ford 2.0 is so good because I can turn it 10,000 RPMs. I have no doubt that I can turn it that many, but I have found my best success at around 7400. This is comparable to what my dyno sheets say.

As another side note, I once mistakenly turned a Ford 2.3 10,000 RPMs for a race weekend. The engine was unhurt, but I went considerably slower than I should have.

The moral of all this is to not worry about what other people are doing, even if they are running in front of you. Concentrate on optimizing your car and your driving and if it is possible you will catch them.

bigcityracer
Dirt Freak

Total posts: 431
posted January 02, 2004 12:47 PM  
With all gearing choses give, your best combination would be running the 2.14 trans with the 3.55 rear gear. As posted above the cam is made to work with in the ranges they provided. Give or take 500 rpm. I do run higher rpm, but I have the proper cam for it. There is more speed in proper handling than anyone other area. The straighter you run thru the corners the faster you will be. Less sliding.


quote:
Originally posted by Trapper:
I am running a 7.5" rear end if im not mistaking. The guy who I bought the car from threw in all the gears so I havent had to order any. The gears I got in the deal are as follows. 2.78, 3.08, 3.27, 3.55, 3.73, and a 4.10. The transmissions I have are all either 1.94 or 2.14 2nd gear.

TRAP



tay27tronnie
Dirt Full Roller

Total posts: 37
posted January 02, 2004 02:49 PM  
Trapper: e-mail me at tay27tronnie@alltel.net I will give you some goodys.

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tay27tronnie
Dirt Full Roller

Total posts: 37
posted January 03, 2004 03:38 PM  
Trap: hope it helps.Talk to me here or e-mail me I'll help you.

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speedyd1
Dirt Maniac

Total posts: 170
posted January 04, 2004 03:43 PM  
i must have gotten lost somewhere on the way to the track.. i dont know anybody - and i mean anybody that runs that high a gear ratio in a mini stock. ive run 3/8 asphalt and dirt for several years and had many wins at several tracks not only in stock trim but also modified and pro four classes. usually we see 1.99 and 2.14 and 3.08 and 3.18 on occasion. maybe even a 3.27 once and a while. nothing anywhere near what your running. are you using hydraulics or solids in your heads. do you not float valves above 7000 with hydraulics. i turn 6500 to 6800 with my 1.99 and 3.08 all day with our stock minis on a flat to moderately banked track. you should be much higher than that with your final ratio. what gives???????????
I'm so confused!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

speedyd1
Dirt Maniac

Total posts: 170
posted January 04, 2004 03:51 PM  
have someone run some simulations to see where your peak torque and hp are. then you can gear your car accordingly. you'll want the car to have peak torque off the corners and peak hp at or near the end of the straights. unless the other guys are running your same setup under the hood you should avoid using any gear they are and focus on gearing your car for the particular cam you have. send me some specs and i'll run the sims for you and email them back. speedyd1@AOL.COM

CLIFF73
Dirt Roller

Total posts: 24
posted January 05, 2004 02:45 PM  
So what is the final drive formula?

b4racing
Dirt Forum Champ
Total posts: 626
posted January 05, 2004 04:28 PM  
the gear ratio that you are using in the trans X rear gear = final
for instance I run a 1.97 second gear X 3.27 rear gear = 6.44

racerman707
Dirt Freak

Total posts: 374
posted February 06, 2004 04:11 PM  
trapper,kieth blacks will turn 7500 easy.as long as ring gap,wall clearance is RIGHT.i dont know how many will agree but a crane will hold you back!schneider is almost same price as crane and you will be surprised at the difference in power. as far as gear,we never ran lower than a 680 gear on 3/8 track with med bank and turned 7800 plus.make sure spring pressures are around 110# closed and 230# open on hyd.and solid (not roller)106 or less lobe sep single pattern cam and hold on tight!!! ps be sure your geometry is right.

bigcityracer
Dirt Freak

Total posts: 431
posted February 06, 2004 08:09 PM  
quote:
Originally posted by speedyd1:
i must have gotten lost somewhere on the way to the track.. i dont know anybody - and i mean anybody that runs that high a gear ratio in a mini stock. ive run 3/8 asphalt and dirt for several years and had many wins at several tracks not only in stock trim but also modified and pro four classes. usually we see 1.99 and 2.14 and 3.08 and 3.18 on occasion. maybe even a 3.27 once and a while. nothing anywhere near what your running. are you using hydraulics or solids in your heads. do you not float valves above 7000 with hydraulics. i turn 6500 to 6800 with my 1.99 and 3.08 all day with our stock minis on a flat to moderately banked track. you should be much higher than that with your final ratio. what gives???????????
I'm so confused!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

I RUN A 1986 COROLLA 3TC MOTOR TRANS GEAR 1.94 AND REAREND 4.11 = 7.97:1 CAR IS VERY FAST TURNING 8,000 RPM 3/8 MILE DIRT TRACK.

MOST MUSTANGS AT MY TRACK RUN 2.14 WITH THE 3.27 REAREND GEAR. FINAL 7.00:1


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