How much would I expect to pick up going from a 2.73 to a 3.42 or 3.73? I picked up .5 with just a converter swap to a 3200.
Regards
Skip in Michigan

 

Before you cowboy into a gear swap let me quote someone about how to make a car fast.

"Well, you need to know where you'd like to put the peak hp and torque. You will need to gear the car to optimize that envelope if you hope to have everything work together. If an auto, you have to choose a stall converter that will work with that rev range as well. Keep in mind that you will need a thicker power curve for a 4-speed auto than a 6-speed manual... even broader for a 3-speed auto.

The tranny plays a big part in the cam selection as you see... it also plays a big part in the way the cylinder head should be prepared... not to mention the intake and all airflow prior to it. Alot of people miss this part.... the really fast guys don't."
Mindgame

With so many variables involved I would wait until you know exactly what you want to do with your car before you get gears.

Rich

 

Okay, I know where you're coming from. Here's what I did. First came the 3200 converter to get the rpms up to the power band of a stock LT1 off the line. That netted me a .5 sec drop in ET right there. Then I tried to do my homework, thinking about the cam and heads and presently running nitrous and possibly a SC later. That and running dyno simulator software I experimented with different cam profiles and decide to go with a 233/242-.569/.576 at 114* Comp cam. I bought a set of "ported" stock valve LT1 heads and roller rockers. I went with this cam because I didn't want to go tamer and then buy another cam later. I also went with 30# SVOs and installed Edelbrock shorty headers and removed the cat.. The only tuning the motor got was to bump the timing up to help with the idle and the injector constant change for the injectors.
The history of the car is: Stock -14.40's, After converter install -13.80's and after the heads/cam Cnsistant =13.40-13.50's. In another post I talked about the car running the same numbers for the first 1/8 mile as it did with just the converter swap but picking up another .5 after the 1/8th. That's why I ask if swapping to a different gear would help.
I appreciate your reply as I see a lot of guys throw parts at a cr because someone else did it. At 50+ years old I've learned the "hard way" to try to do my homework first before the wallet opens up I believe there's more left in the motor as it sits now with some professional tuning but I'm still looking down the road and I don't know many guys that run any kind of numbers with a 2.73 so that's what my next mod was going to be.( I'm going through the traps now at only 4200 shifting into 3rd about 100 feet from the traps. That's shifting at 5800 1-2 and 2-3)
Thanks for the reply, looking forward to more correspondance and insight from your point of view
Regards
Skip

 

Do you have a dyno graph that I could work with? Since your an auto your want your car to make more power in the middle rpms then choose a gear to optimize your time in that powerband.

Rich

 

Rich, unfortunately no I don't. I know that's what I need to see just what the motor is putting out. After I get back from St Ignace next week I'll probably schedule some dyno time. I'll keep you posted though
Thanks again for the interest.

 

you sadi you ran 13.4 13.5 consistantly...what was the MPH? that plays a huge roll in gear selection. Are you gonna be running a 28 inch tire when you run on the spray or at 26 inches, or even stock tires? Are yo spraying out of the hole?

 

3.73's, the bigger the better.

 

Not always true, but 3.73 seems to work pretty good with a 4l60e tranny and h+c

Rich

 

102mph,MT Sprotsman Pros at 28" or BFG Drag Radials at 28" and no. I believe the car should run as it sits motor wise into the 12's Unless there are a lot of liars on the net there are a lot of cars running 12's with less cam and heads than what I have . The common denominator for those guys is that none of them run 2.73's
Skip

 

On a side note I talked to a racer with some 40 years experience with SS cars and told him about my car and his immediate reply was "you need more gear" without me even telling him what gears i had.

 

the 28 inch tire is too large and is making your gears seem even smaller. You need to go to a 3.73 minimum with those tires and thats if you are gonna spray. If your not gonna spray but your gonna stay with a 28 inch tire... go with 4.10's.....you just have a really bad gearing combo. too large of a tire, too tall of a gear, and not enough hp to do anything about it. Best thing you can do is go to a 26 inch tire or put a stock sized drag radial on your wheels(best thing to do), get some 3.73's, and you will notice a HUGE difference in your car. You wanna be crossing the line at about 5500-5600rpm with the stock rev limiter, not 4200...thats just plain insane, lol. I garuntee with a 26 inch tire or drag radials, & 3.73's, you will prolly pick up another .5 minimum. Your car doesnt have a short enough effective gear ratio to get out of its own way