Switching headers, RPM change

[Doug Riparetti]

I raced my car the 1st time, last race of the 2006 season with the standard 1 3/4“ to 1 7/8” stepped headers, 604 motor. I just switched to the 1 5/8” to 1 7/8” crate headers and I am going to practice in a couple of weeks. 1/4 mile, dry slick, semi-banking, I was on the chip half way down the straights before, I have a 686 gear in it now, what gear should I run? New to late models, crates etc…. and I need to purchase gears and I do not know what to expect regarding RPM change, is it going to come on sooner, due to the better torque making me run out of gear and on the chip quicker, need help?

[Chris Steele]

Not sure about the header change, but I honestly don't think your gonna see much of a RPM change, mainly just a move in tourqe throughout the RPM range. You should try to borrow some gears from someone to test with. Buying a bunch a gears can get expensive unless someone that runs your track can put you in the ballpark. What rev-limiter chip are you using?

[Doug Riparetti]

6600 chip

Doug

[Chris Steele]

I would try in the 600-630 range as a starting point. It's better to have too little gear as opposed to too much.

[ScottyRocket]

Chris is right. It will affect the power peak(torque peak), so it will have an effect on where the torque comes in... but it won't affect the rpm range. The change will likely give you a touch more torque(maybe 10-15 ft-lbs) down low, but could take some peak power away or just move it down the rpm range....can't really say for sure without a dyno.

You are limited by the chip, so if you are hitting the rev limiter half way down the straight, make sure you'er not spining the tires so bad that its making it do that...then just put in less gear. You want the rev limiter to hit right about the time you are letting off for the corner...or even a little before(without spinning the tires)...that gives you a little room to play with gear once you have gotten it close.

[Doug Riparetti]

Thank you for the info

[wilder11354]

http://www.circletrack.com/searchresults/?scope=T&sitename=circletrack&terms=Gear+Ratio&x=13&y=7

theres several articles covering this in this Magazine.