[Doug Christie]

I used a "shift point calculator" to determine at what point to shift. It's the kind that you imput all your rpm and torque data from 2000rpm to your red line, in 500 rpm increments.

It tells me I should shift at 5500 to have the same power above the curve as below. I think I should be shifting quite a bit lower, say 4500-4800. Anybody,know?

[Doug Christie]

I used a "shift point calculator" to determine at what point to shift. It's the kind that you imput all your rpm and torque data from 2000rpm to your red line, in 500 rpm increments.

It tells me I should shift at 5500 to have the same power above the curve as below. I think I should be shifting quite a bit lower, say 4500-4800. Anybody,know?

[harry k]

5000 to 5200 sounds like where you should shift ,tell me again whats the cam specs on that speedpro cam???

[Doug Christie]

Cam specs are @.050 224/234, .465/.488, 112 LSA.

Valve Open:BTC 5*,ABC 39*
Valve Close: BBC 54*, ATC 0*

[harry k]

i would say 5000 rpm now with your combo ,seen many times some of the pontiacs i dynoed ,the owners almost always were over reving before,after they knew where their power peak is on the dyno ,they went faster and lil quicker the next time they were out.. tryed and see if it will workk out for you

[PHILLYGOAT]

Pretty mild cam. Try 4800rpm.
PHILLYGOAT

[grandville455]

Geez Doug if you shift at 45 to 4800 My cam is smaller yet maybe i should be shifting at 42 to 4400...instead of 4800?

[DAVE RIBEIRO]

Find a test n tune track and bring nothing but a pen and pad of paper..Have a game plan,
something like this..Make a run shift at 4,200+
4,400.Then a back up run to duplicate the first
time.(always Two-runs) write everything down on the paper,engine/temp,launch rpm,shifts,ET/MPH,
tire pressure,etc. Next run,shift at 4,500/4,700
do two runs,and so on up to 5,500..Moving a couple hundred RPMs at a time..My racecar will pick-up 3-5 hundreds by short-shifting the 1-2
shift..I use 4.56 gears,track only...Pontiacs
are usually over shifted,they make most of there power down low 5,000 to 5,600 range..But guys still try shifting at 6,000 ??? I do this at least once every couple years to see where the car really likes to be shifted at and make the most power..It also will run the fastest ET
at that point and you will then know..good-luck
and keep good notes..Most good racers can tell you what they ran 2 years ago and what the weather was that day..Practice,Practice,Practice
wins races..Good-Luck on your testing...
Dave...1033/stock

[Doug Christie]

Thanks Dave, I was hoping to avoid doing all the testing again and just plug numbers into a formula and have it spit out the magic number.

I do keep good notes and can go back to every race I've done.

[ERIC17621]

Pardon me for interrupting, but I find it hard to believe that a calculator could actually figure out a shift point without providing it tons of info. Cam is a good start, but it should also know things like VE, bore/stroke ratio, head flow. All of these will effect where an engine makes power. What type of info do you provide to this calculator?

[Doug Christie]

Eric, it will be similar to the on below. It was an online thingy.

http://www.prestage.com/carmath/dynochart.asp

[Taff]

My 400 powered race car sounded and felt quicker when shifted at what I thought would be the optimum point-6500rpm- but it runs 3-4 tenths quicker shifted at 6000rpm. As Dave said, you've got to experiment constantly,virtually any part of your combo that you change will affect something else.

[A.W.Dille]

Well alot of it depends on what the engine likes. Mine when I was running the RAIV cam it liked 5800, with the Lunati I'm still trying to figure out what this cam likes, right now I have the light set at 5600, and have tried everything from 4800-5400 with no improvment in times. I would try around 5200-5400 to see what the engine likes, may do better at 4800-5000, it depends on the engine and sometimes track conditions, along with air. There can be alot of variables but I normally go by the range of the cam and start there.

[grandville455]

We'll I know with my car if you shift it around 4300 to 4500 it chirps the tires in second but if you go higher it doesnt .Does that mean i should shift there?It seemed like the higher i shifted the mph was there but not the et,,whats that mean?

[A.W.Dille]

Well I remember a guy used to bring a weather station to the track with him when I raced at National Trails. Even though I didn't fully understand how to read it I found out the barometric pressure and humidity played a crutial part in evry cars performance and he would run his car accordingly,he would change his shift points and launch techiques according to what he was reading on that small station. Still don't fully understand it but now I like to listen to weather before I go to the track so I can have some idea of how the weather is going to be as far as humidity, helps on tuning also. Also helps figure on track conditions also, factors in figuring shift points and launch techniques.