Best gear for 9.90
 

What is the ideal gear for a 2600 lb tube chassis car with a 582 BBC and glide? Been running 4.10 with a 33" tall rear tire and it seems as it is hard to recover off stop and it wants more gear, say 4.56?

Thoughts?

Re: Best gear for 9.90
 

Finish line RPM kinda puts you in the ballpark

Re: Best gear for 9.90
 

Would the 4.56 help coming off the stop to recover?

Re: Best gear for 9.90
 

I agree that I'd base the rear gear choice on finish line RPM. As for recovery coming off the stop, you can try a higher cruise RPM, coming off the stop in low gear, going on the stop later to get the car moving, etc.

Re: Best gear for 9.90
 

While it is true that finish line RPM plays a part, I was convinced a few years back by Eddie Jr, at Select Performance, to go to a 4.56 gear.. not only to enhance his converter set-up, but that I would be surprised by the charge coming off the stop.. I now have 2% to 3% slip in the converter at the top end, and that charge coming off the stop is awesome, and I go out the back door at approximately 7600 RPM with my 565.. I am only 2150 pounds also..

While I was a nay-sayer, until I switched from the 4.30, I doubt I'll go back.. while it slightly increased the RPM, I didn't seem to affect the MPH at all...

Re: Best gear for 9.90
 

Are you saying that the car comes off the stop much harder, your converter got more efficient, but you didn't gain any MPH?

Was there a measurable gain anywhere? Could you stay on the stop longer?

Re: Best gear for 9.90
 

Although I didn't mention MPH, I'm up between one and two.. also, I usually do stuff to try and take time out of the box.. not put more time in.. and I really don't like carrying 3.00 in the box either...

Re: Best gear for 9.90
 

rob7181,
Going from the 4.10 your running to say a 4.33 would only be a 5% increase, but going to a 4.56 is going to be a 9% overall increase in performance. Plus you should pick up around 3mph.

Re: Best gear for 9.90
 

Like Charlie ,I run Select converters . I went to 4.56 gears from 4.29 in my Vette which weighs in at 2400# .
I picked up 2 mph with an increase of 250 trap rpm .
converter efficiency went from 10% slip to 5-6%. AND very importantly , the converter temperature dropped way down when coming off the stop.
Since Charlie's car is a '27 Roadster, one of the hardest cars to get MPH out of I'm not surprised by the lack of improvement in speed.
I would defiantly recommend 4.56 gears in your car.
Racers get too hung up on trap rpm's , if your engine is still pulling at the stripe ,let it eat !

Re: Best gear for 9.90
 

^^^^^^this