[M&M]

I've been tinkering with the governor in my turbo 400 behind my 455. Got it shifting at about 5200, maybe 5300 rpm. Factory tach, don't know how accurate. Is that too high for a stock bottom end? Used to shift at about 4500, wondering if I got carried away. Doesn't feel like the power is falling off yet, just concerned about the revs.

Thanks
Mack

[lust4speed]

Piston speed really gets up there with the longer stroke, and the rods receive a lot of punishment. If the rods have never been out of the engine, I would tone the RPM down to no more than 5,000 RPM since you really don't know what shape they are in. If the engine has been rebuilt, but with stock rods and bolts, then the 5,200-5,300 RPM would be safe.

If your engine is stock, you're probably better off shifting no higher than 4,800 RPM. The upper end horsepower with a stock setup won't be near as quick as having it shift up and letting the 455's torque do its job.

Everything just needs to be kept in balance. Aftermarket rods and pistons will safely allow higher revs, but then you need headers and a well chosen cam to see any improvement holding the shifts.

Also, my factory tach in my '67 goat was dead on when I checked it against an Autometer tach.

[Half-Inch Stud]

455 shift point REASONING:

Performance; Shift @CLY Head "Choke RPM". (shift early if unported iron)

Bottom-end; A man has got to know his rods' limitations.

[M&M]

Thanks.

Heads are 260cfm 6x#4 from SD. Cam is a TC-02 from Pacific. Still pulling good at those revs, but I don't want to be thumbing home just because I spun it a couple hundred revs too high.

[Lee]

My first 455 ran a full .5 quicker at the track when shifted at 4600, compared to 5000. It was still "pulling" at 5000, but a torque motor needs to be where it is making torque to run the best. If it hits REALLY hard after you shift, you are probably shifting too late.

NEVER trust your butt, it WILL lie to you!

[Lloyd-TX]

Great advice, Lee!

[ta man]

Found the same here years ago with a more stock cam in a 455..shifted at 4800 for best et.anything higher lost et as much as 2 tenths.

[jonmachota78]

My stock tach reads about 500 rpm LOW in the 5000 rpm range. So I'd say check your tach to make sure you're where you think you are. Jon

[Lee]

Originally Posted by jonmachota78

My stock tach reads about 500 rpm LOW in the 5000 rpm range. So I'd say check your tach to make sure you're where you think you are. Jon

Excellent point! My old tach MAY have been off - I don't know. I'd shift the tranny manually to find the shift point (as indicated on the tach) that provides the best performance, then modify the tranny to shift at whatever that indicated value may be.

Lee

[M&M]

My thanks to everyone. I'll pull the shift point back down some.

Mack

[General Z]

Originally Posted by Lee

My first 455 ran a full .5 quicker at the track when shifted at 4600, compared to 5000. It was still "pulling" at 5000, but a torque motor needs to be where it is making torque to run the best. If it hits REALLY hard after you shift, you are probably shifting too late.

NEVER trust your butt, it WILL lie to you!

This comment really has me thinking. I've got another thread going regarding my car feeling like a dog in spite of a pretty decent build on paper. I've got a 700R4 that shifts around 5000.

[steve25]

The best way to get the right answer to your question without getting the motor on a dyno, or the whole car on a chassis dyno is this.

Find a nice l long level stretch of road.
Get the car moving in high gear and once the revs are above 3000 rpm floor it.

Then make a careful mental note of the rpm where the revs stop rising fast.

That will be the rpm of peak torque and will be the rpm you should be making your shifts take place at.

Do this a few times to be certain of what your feeling and seeing on the Tack in terms of the rpm rising.

If your trans still wants to down shift above 4K rpm then disable the down shift cable or switch, whichever you may have.

Testing for the rpm of peak torque since your not on a dyno must be done in high gear.


Just note that your playing with fire here in terms of the stock rods and the 4.210” stroke of the 455.

For cruising rpm with the 455 you should try and keep the piston speed below 2500 fpm if your running the heavy stock pistons on the factory rods, problem is at 4000 rpm the piston speed is already 2800 fps.

[i82much]

there is no way you want to shift at peak torque rpm if your goal is to maximize acceleration?

[62posbonny]

And NEVER disconnect the TV cable on a 700r4. That cable controls line pressure as well as shifts. Disabling is the fastest way to kill the transmission.

[steve25]

When a 455 street / limited strip motor is set up with the right rear gears the torque band is nice and wide and can easily shift at peak torque.

Please note that a posted to disable the shift cable, not just disconnect it and not have it rest in the Carb idle position.

[Cliff R]

"Heads are 260cfm 6x#4 from SD. Cam is a TC-02 from Pacific"

Specs on that cam?

Compression ratio? What are the rest of the drivetrain specs? Converter stall, gear ratio, tire diameter, vehicle weight?