[max 93]

What do you guys recommend for a shift point on this engine ? My trans is currently set up to shift at 5800. Should I lower it a little ?

[steve25]

You want to shift at a rpm so that the motor drops back as close as possible to the motors rpm of peak Torque.
All motors gain rpm the fastest in what's call the peak Torque cradle,and that in turn accelerates the car's mass the fastest!

[slowbird]

Originally Posted by steve25

You want to shift at a rpm so that the motor drops back as close as possible to the motors rpm of peak Torque.
All motors gain rpm the fastest in what's call the peak Torque cradle,and that in turn accelerates the car's mass the fastest!

Not true at all!

[steve25]

Maybe you should try it one day , you might go faster!

[pastry_chef]

Originally Posted by steve25

You want to shift at a rpm so that the motor drops back as close as possible to the motors rpm of peak Torque.
All motors gain rpm the fastest in what's call the peak Torque cradle,and that in turn accelerates the car's mass the fastest!

Also disagree.

Acceleration NOW in G = (HP x 375) / (weight lbs x MPH)

Aero and rolling resistance not factored in that formula.

[pontibeast]

Originally Posted by steve25

Your welcome!
Sorry to hear about that motors demise!

Thanks long term probably the best thing that could of happened as I finally built the 455 I had been wanting for a really long time. Now all I need to do is find a shop around here that can do the install as my guy has had it for 5 months and nothing has been done. ARGHHH!

[steve25]

Hey folks, wake up and look at his dyno graph details for God's sake!

His Torque and HP numbers have both nosed over at 5500 rpm, if he shifts right there then the normal 800 to 1000 rpm shift/ gear change drops him right back to his Torque peak at 4500!
If you don't think that this works then tell that to for instance all the 455 racers who shift at 5800 to 6200 max and run numbers way faster then a ton of street strip car making far more power!

[slowbird]

Originally Posted by steve25

Maybe you should try it one day , you might go faster!

Maybe you should step away from the keybaord once in awhile. Not 1 fast car ever sees peak tq rpm at any point under load during a run. You can argue all you want but you're wrong, period!
Fyi i have tested it and i have racepak data to back up what i am say along with discussion with many fast Pontiac guys and fast guys of many other makes.

[slowbird]

Originally Posted by max 93

What do you guys recommend for a shift point on this engine ? My trans is currently set up to shift at 5800. Should I lower it a little ?

There is no way to answer that, the dyno only went to 5500rpm, we have no idea what it does after that. 5800 is a decent place to start and go up and down from there to see how it reacts.

[Cliff R]

For many combinations, like my own, the shift point has little impact on ET or MPH. This simply happens due the gearing and tight converter being used more than anything else.

I can shift at 5000rpms or clear up where the engine makes peak HP at 5800rpms, or even at 6000rpm's or higher and there will be very little difference in ET or MPH.

The engine simply makes so much power (torque) over such a broad rpms range that it really doesn't care where you shift it at. The extreme spread of ET between 5000rpm shift points and clear up at 5800rpms is no more than .02-03 seconds.

Completely DIFFERENT deal for some of the dedicated "race" cars we have set up here, but that information is better used in the "Race" section instead......Cliff

[slowbird]

Originally Posted by Cliff R

For many combinations, like my own, the shift point has little impact on ET or MPH. This simply happens due the gearing and tight converter being used more than anything else.

I can shift at 5000rpms or clear up where the engine makes peak HP at 5800rpms, or even at 6000rpm's or higher and there will be very little difference in ET or MPH.

The engine simply makes so much power (torque) over such a broad rpms range that it really doesn't care where you shift it at. The extreme spread of ET between 5000rpm shift points and clear up at 5800rpms is no more than .02-03 seconds.

Completely DIFFERENT deal for some of the dedicated "race" cars we have set up here, but that information is better used in the "Race" section instead......Cliff

Good post, i agree

[70GS455]

The best way to determine optimum shift points analytically, other than do a bunch of dragstrip runs, is like in the attached picture. Plot the dyno info for each gear, tq or hp doesn't, the math works out the same. Where the tq or hp in the current gear falls below (i.e. they cross) that of the next higher gear, that is your shift point. If they don't cross, shift point is engine redline.

Note the pic is of tq, hp can be done the same way, it's just the value won't be multiplied by gear ratio, but the rpm will still be divided by gear ratio.



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