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Author Topic:   rear gear choice? with engine size?
posted August 02, 2004 10:48 PM
Just wondering how you folks determine what gear size to run, I will be running on a 3/8's mile track in wichita,

I dont know what you need to determine this so here is my engine specs...

lightweight scat crank
h-beam rods 6 inch
double hump heads
racing water pump,
180gph mechanical fuel pump
moroso water pump pully 50% reduction
moroso crank pully 30% reduction
pete jackson gear to gear drive
KB pistons-
Effective Head Volume: -11cc
compression is around 14.5

the cam specs
Internal Duration @.050" 256
External Duration @.050" 264
Internal Lift 545
Exhaust Lift 563
Lobe Separator 105
Advance Internal Duration 287
Advance Exhaust Duration 295
Valve Lash .026-.026

stock exhuast, might be going to headers...
roller rockers, 1:6
isky springs....

I havent chosen a carb yet, rules say any 2 or 4 barrel carb, waiting on them to answer a few questions before I go buy one, so if anyone runs at 81 that knows this let me know.

everything has been ported etc.....

if anything else is needed let me know

posted August 02, 2004 11:22 PM
also on the tranny..

I have 3different ones

a 2 speed powerglide, that has been modified for racing.....

a stock 350t

and a 3speed saginaw

if anyone knows what would be best forr this setup let me know......

posted August 03, 2004 05:37 AM
First question is what class you running and what is the weight of the car? I've run the T350 using 1st gear (2.52) in my street stock @ 3300lbs with less engine and 2.73 rear gear (6.88 total). Turned 6800rpm on a really fast .3mile with no trans problems. Currently running modified T350 with straight input shaft and valve body from TCI in my one mod in 2nd gear (1.52) and 3.73 rear on same .3mile track and fast flat 3/8 mile. Turn between 6800rpm and 7100 with a good 355. Lastly, I run 383 with the saginaw in 3rd with 5.67 on same tracks and turn about the same rpms as the other mod. Hope this gives you some ideas.

Rat Trap
posted August 03, 2004 05:42 AM
the class is street stock, with my engine size the car cant be below 3500..lbs

posted August 03, 2004 09:23 AM
Hey Pandora. If you're running street stock and they require you to run a torque converter when using the automatic, I'd suggest running the saginaw with a good clutch. The overall assembly weight is lighter than the T350 and converter combination. That way you can place the ballast where you need in the car for handling and minimize centrifical weight. Granted, I ran the T350/converter due to it's what I had at the time and it matched the weight distribution in the car. I also used a window AC condensor as my trans cooler mounted inside the car away from me (safety reasons) and never over heated the trans. As for the gear, anywhere from 6.50 up will put you in the ballpark. You should have some good torque with the 383, so I would not hesitate on maybe leaning towards the 6.50 gear depending on RPM range you want to run. If you need more pull off the corners, then consider the 6.80 range gears. Good luck

Oh, as clarified, I'm talking about total gear ratio depending on trans/rearend combo you use.

[This message has been edited by smayo964 (edited August 03, 2004).]

posted August 03, 2004 11:36 AM
6.50 will be a grunt off on tacky but if the track is dry slick I would think it would be a little too much. 383's build good low end I would start 600 or 620. This is based off running a scuff tire of about 83" roll. What tire does 81 run now? I have a cousin that used to race there, I'll call him tonight & ask what he ran.

posted August 03, 2004 12:35 PM
Stock exhaust?

If you're stuck with the manifolds, I'd aim for 5800-6000 max and use the torque of the 'big' motor and not wring it's neck for no reason.

What intake do you have to use? That will play a big roll in what rpm it's gonna be happiest in too.

Ohh.. and that cam's pretty **** big for running factory manifolds. Gonna be way out of it's real powerband. I'd switch to the headers right quick (1 3/4" tubes would be a good starting point).

How many folks out there are spinning over 6000 with a 383 or 400 and factory manifolds? I hope not many.

posted August 03, 2004 01:04 PM
I'm running a 406 Chevy, 88" roll tires,
1.75 (2nd gear) x 3.50 (Rear Gear)= 6.125 final

3/8 track, 5,800 rpm and I can pull with them.
I would like to turn a little more, i'm thinking about investing in a 6.20 gear.

I'm not positive, but isn't 1" of tire roll worth about 100 rpm??????

[This message has been edited by Flanndad (edited August 03, 2004).]

posted August 03, 2004 06:02 PM
Cousin said he ran 620. I'm with the other guys on the manifolds, get some headers. As far as rhe cam it is a #2 mw or jr? That is what I run in a bomber/street stock class at Jetmore KS. It will work just fine. I run a 355 with cast intake & ram horn ex. Turn it 6700 every night.

posted August 04, 2004 05:46 AM
Dirtbandit, I'd go with something in the 5.43 or 5.67 range. We have a huge and fast 3/8" just built here with gumbo surface. The track measures 3/8 mile 10' off the bottom and is 85' wide. I've questioned some of the people I run with and we're using one of the (2) ratios I've listed. You'll be anywhere in the 6800-7100 range depending on gear.

posted August 12, 2004 08:19 AM
never ran at that track,but when I ran factory stocks,basicly the same type of car you have looks like,I ran a 6.80 and it was a good sized 3/8.
The track I ran at was Oklahoma Sports Park in Ada Ok.

posted August 12, 2004 11:33 AM
i run a 6.24 0n a 3/8 mile track with less motor so if i were you id start with a 6.33

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