i always shift higher than the power peak, the rpm drop will then be closer to the power peak, where the engine is making more power.....helping acceleration. I assumed most people knew this.

 

I agree with Darth. Go for 7200 if you're confident your engine & transmission are ok there. If not as high as you dare.

I'd stick with the 3:42 gear unless it's a dedicated strip car.

 

Ideally, you would have tq and hp curves to see where peaks are. Shift where drop back rpm is just north of peak tq. Based on hp graph I'd expect hp to start dropping off around 6800. Peak tq likely around 5300 to 5500. With some track testing or draggy times, start shifting at 6800 and go up 100rpm each test to 7300 and see where it performs best. Datalog to see drop back rpm and recovery.

What is intended use, race weight, and tire size to determine rear gear?

 

Intended use is a weekend street car that will see the track once or twice a month. Race weight is stock to maybe a little more. Tires are 26.42".

 

I've always heard to shift about 500 rpm past peak hp but that depends on where your rpm limiter is set and how much faith you have in your rod bolts.

 

ARP rod bolts.

 

We like our converter to only drop 1000 rpm at full power on the shift. This will keep you dead in the power band. So you want to do the 1-2 shift where it drops it back to the beginning of peak torque. Then the 2-3 shift we string out to drop it back to just under the beginning of peak Hp, so when your going thru the traps your just above peak Hp.

For example, our motors max torque starts at 5800 rpm and carries with very little drop to 6200 rpm. Being our rpm only drops 1000 rpm on the shift we shift 1-2 at 6800 which is the beginning of our max Hp. Then we do the 2-3 shift at 7400 rpm so it drops back to 6400 rpm. Right in the middle between the top of peak torque and just before peak Hp which is only a few Hp less than peak. We run an electric shift solenoid so shifts are dead on. This is how we achieve our best 60ft, MPH, and ET's.

Since no one hardly races 1/4 mile anymore and being you have no power adder. Concentrate on the 1/8th, that is what most races are anymore on the street and the track. I would go to the 4.30's if your running 28" tires or a 3.90 if they are 26's. If its a track mostly car, then 4.10's on 28's or 3.73's on 26's if its a street mostly car. The 4L60 has a lower first gear so that will help. At full weight you have to get it out of the hole to get your 60ft down. Then you have to get it to the ground without spinning. If you can't data log, put a camera on the tach so you can see how much it drops on the shift. Then look at your numbers sheet from the dyno and shift it accordingly. If you ever do use a power adder, the more power you through at it the more loose the converter will become so you have to adjust everything accordingly.

 

I agree with the guy above 3.90s with your current 26.4in tire will work great. That’s the route I’d go in your shoes.

 

3650 race weight at current 430whp should trap 94mph in 1/8. Rev to 7300 with 26.4" tire and 5% converter slip in 2nd gear (1.625 ratio) would use a 3.55 gear (10.86 SLR). With a good converter and tire/suspension working well, car should perform well.

 

Thanks everyone for your input. Once I get the car back together and get it to the track I will report back.