Right now i am running a 4.10 gear but i am going through the lights at 5800 rpm in the 1/8th and my rev limiter is set at 6200 rpm. I am wanting to run the car in the 1/4 mile but i cant unless i make some changes. I picked up a 3.55 gear and was planning on putting that in the car but im not sure if i can. I am running a tci stall converter that stalls at 4200 and a tci c6 tranny. Would it be ok to run the 3.55 gear with this setup? It doesnt see alot of street driving but it does see some.

 

How tall are the slicks?

Lots of guys run 4.10's in the 1/4.

 

Im runnin 275/50-15 MT ET Streel Radials, i just didnt know if i could run that gear on the road because the converter will be slipping almost the whole time. I didnt want to burn anything up. I plan on building a new setup that will turn around 10,000 rpm one day but that wont be for awhile, then i know my 4.10 will be good.

 

10k rpm!!!??? Wow!

Tell us more about your engine. Induction etc.

What hp/tq numbers are you running? What rpm peak torque / hp.

Depending on the powerband, a 4200 stall converter may be a bit steep. The converter could be wasting a lot of power if it's too steep.

 

Right now its is a 347 with all 4340 forged goodies inside, its got edelbrock performer aluminum heads, holley single plane intake, demon 750cfm blow through carb, vortech v7 ysi pushing around 13lbs of boost, full msd ignition and a full aeromotive fuel system. Ive never had it on the dyno but we estimate it around 600hp. When i ordered the converter from tci it said it was a 3500 stall but it stalls at 4200. Ive got my rev limiter set at 6200. Ive never had the new carbureted setup running yet but this is how it was when it was still EFI.

 

Nice setup!!

My race math ain't the greatest but from what you said:

You should be running low 6s @108 (5800rpm, 25.8in tire and 4.10s) in the 1/8th which would be around 10.0 @ 135 (660 mph X 1.25) or so in the 1/4.

The problem is that puts you at about 7500+ rpm in the 1/4.

A dyno run would help. Ideally you want the to stall a little lower than where your peak tq is. It may be OK where it is. Then you gear and pick a tire size. I liked the 10% rule = over gear by 10% and play with the limiter.

You might need to try a taller tire.

Is your car tubbed?
What is your 60 ft?

Some else with a bit more recent experience may need to chime in. It's been a while for me.

 

OK after thinking about this some more

Do you run a trans brake? or foot brake?
How does the car launch?
How much room do you have in the rear wells?

IMHO, a taller tire would get you there but it would need to be about 31" tall.

If you have room in the wells a taller tire is the best bet. One set for the street and one for the strip.

 

Right now im just using the foot brake, when i ordered my tranny from tci i couldnt afford the one with the brake. The last time i had it at the track i ran a 7.14 ET with a 1.55 60ft. I probably could have got some better ET's but my i had a bad shift and got out of the groove a little. I could probably squeeze a bigger tire on there, i would just have to lip the fender some. I put a set of my buddys 28/10.50 ET drags of there once and they fix but rubbed pretty bad. I could probably get by with a tire a little smaller than that one.

 

Adam,

It looks like you may not be able to do all three (Street, 1/8, 1/4) with your current setup. You may need to give it a mini tub to get taller tires in there to run in the 1/4 and maintain your current stall / 4.10. I don't know if rolling the lips would give you enough.

Someone with experience with similar setups might want to chime in. All of my experience is setting up race cars and that was 20 years ago. We would set it up for the 1/4 and change the gear for the 1/8 since we knew what rpm we wanted to be at and tweak it from there. Never tried to run those cars on the street.

I hope it helped but there may be another solution.

 

Ok, well i guess im going to have to go back to the drawing board! Lol... I appreciate all your help!

 

I know this is a delayed question but where did you get the numbers or how did you calculate the numbers to get my ET's and mph?

 

I've got an old notebook with the formulas we used.

And I plugged in the info you provided like tire size, gear and the rpm you were going through the traps.

It's pretty easy if the numbers are good and you know what your hp/tq curve is at that way you know where your setup needs work.