Starting Shift Point

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SpeedThrills

SpeedThrills

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My 360 has a 750 vacuum Holley, Torker II, 11.25:1, ported 915 heads w/ 2.02 intakes, 292-.508 purple cam, 1 3/4 headers, stock rods and crank.
I bought it with all of this and have disassembled it to verify everything. I can’t speak to the quality of the port work. I don’t know who did it, and I don’t have any experience with port work.
Anywho, what’s a good shift point to start out at?
 
Gear and tire diameter? Stick or auto? I'd guess short shift out of first (5500) and then 6300 . See what the trap rpms are and adjust from there. I'd guess that cam would pull to 6300 or more if it's dialed in right.but a guess without more info.
 
I only have experience with that cam and setup in a 440, and it is out of wind at about 5,600 and falls off fast.

I'd start at 5,500. Make a pass and up the shift point 200RPM each run until you see your time falls off.
 
More info:
It’s a street/strip car that will see very little street.
I got the entire driveline out of a wrecked D150 Pro Street truck.
When I installed the cam, it was at 108, so I left it alone.
It’s a 727 w/ roughly a 32-3500 converter. (I just started driving it, so I can check closer.)
The tires are M/T ET Street Radials. 235-60. They’re about 26” tall.
The gear is 4.11 (9”). I may be changing that; it has a pretty bad howl.
As a street car, I don’t think it’ll see the perfect stall and rear ratio.
All in a 71 Duster clone. It’s pretty light. Fiberglass hood, fenders and bumpers. No back seat, light weight fronts, Prostars, skinnies.
I guess what the cam will pull to is my main question.
 
Want to really find out?

Strap it to a chassis dyno.

The other way is to take it to the strip.

The way most simps do it is keep their foot in it until you feel the pull subside then shift. Not a very good method.
 
roccodart440 said:
Want to really find out?

Strap it to a chassis dyno.

The other way is to take it to the strip.

The way most simps do it is keep their foot in it until you feel the pull subside then shift. Not a very good method.
Click to expand...


Not good for a hydraulic setup, that's for sure. They're all different, though. Combinations change everything.
 
Agree with Valiant 528, and Rocco. Start off shifting at well short of BOOM rpm, probably 5500, then move shift rpm up a couple hundred, and see if it gets faster or slower. If I had to guess, I'd pick 6000-6200 as the sweet spot.
 
roccodart440 said:
Want to really find out?

Strap it to a chassis dyno.

The other way is to take it to the strip.

The way most simps do it is keep their foot in it until you feel the pull subside then shift. Not a very good method.
Click to expand...
You can also do this with one of the in car performance monitors. What you want to do is generate curves where they intersect for the gear changes for "anything"---torque, HP, acceleration. You shift where the curve for 1st gear intersects the upcoming curve for 2nd gear.

If you cannot generate a curve for every gear, then generate what you can and "figure" the rest from the transmission ratios

best-gear-change-rpm-change-at-the-torque-intersections.png
 
Download a G-meter app, - that works off the accelerometer chip, not GPS.
Place the G-meter near your tach, - accelerate hard, - when the G-meter drops, you just passed your shift point .
Don't be surprised if the shift point is different in every gear .
 
inertia said:
Or download a G-meter app, - that works off the accelerometer chip, not GPS.
Place the G-meter near your tach, - when the G-meter drops, you just passed your shift point .
Don't be surprised if the shift point is different in every gear .
Click to expand...
Exactly the type of thing I was referring to. But this is not quite right. You need the intersect point of the two gears.

"If you can" you want the curve in RPM, not MPH as the example curve I posted. But you can "diddle" it once again, with gear ratios to figure RPM vs MPH.
 
roccodart440 said:
I only have experience with that cam and setup in a 440, and it is out of wind at about 5,600 and falls off fast.

I'd start at 5,500. Make a pass and up the shift point 200RPM each run until you see your time falls off.
Click to expand...
I had that cam in my 440 Charger and it wanted shifted at 6200-6300 (4.10 axle, mild ported iron heads, 800 DP, CH4B intake, 9.4 CR, 4260# curb weight.) Anything lower slowed it down. And ET's were flat up to shifting at 6700 rpm. So I shifted at 6200-ish to save the motor.

You nailed - start around 5500 and move rpm up a couple hundred until you find best times. In the perfect world, the shift would drop rpm back to a poont at the exact same power level thus maximizing area under the power curve. But as always, "your results may vary."
 
I just checked the stall- about 3300 and it overcame the back brakes.
I was thinking about 6000-6200. It’ll get to the track when I sort out a few more things.
I’m too cheap to spring for a chassis dyno. I had to do it to my EFI Mustang. Ouch!
And I’m way too simple for the tech stuff!
Thanks all!
 
I ran that same-ish combo in year 2000, except, I have OOTB Aluminum Edelbrock heads. The power by a G-TechProSS, peaked at 5300 but hung on pretty good. With an automatic, I would try 5900/6000 for the 1-2 shift, an 3 to 4 hundred less on the 2-3. and trap at 5500ish
 
SpeedThrills said:
I just checked the stall- about 3300 and it overcame the back brakes.
I was thinking about 6000-6200. It’ll get to the track when I sort out a few more things.
I’m too cheap to spring for a chassis dyno. I had to do it to my EFI Mustang. Ouch!
And I’m way too simple for the tech stuff!
Thanks all!
Click to expand...
Hang on now. Do you have a manual valve body and did that test in high gear? That's the only way to be accurate, otherwise you're putting too much leverage on the converter in low gear and you'll get an inaccurate measurement.
 
RustyRatRod said:
Hang on now. Do you have a manual valve body and did that test in high gear? That's the only way to be accurate, otherwise you're putting too much leverage on the converter in low gear and you'll get an inaccurate measurement.
Click to expand...
I do have a manual vb. Didn’t think of that. I’ll try it next time it’s out. Thanks
 
RustyRatRod said:
Hang on now. Do you have a manual valve body and did that test in high gear? That's the only way to be accurate, otherwise you're putting too much leverage on the converter in low gear and you'll get an inaccurate measurement.
Click to expand...
So, I understand they make runs on a chassis dyno not in first gear, but if the purpose of adjusting stall is to get the engine into the power band as quickly as possible from low gear. Why? Once you have made the 1-2 shift, the goal of shifting is keeping the engine in the power band? Wouldn’t second gear be a better compromise? Be careful testing stall, it is hard on things.
 
furrystump said:
So, I understand they make runs on a chassis dyno not in first gear, but if the purpose of adjusting stall is to get the engine into the power band as quickly as possible from low gear. Why? Once you have made the 1-2 shift, the goal of shifting is keeping the engine in the power band? Wouldn’t second gear be a better compromise? Be careful testing stall, it is hard on things.
Click to expand...
Get you a copy of the Mopar engine book and read it. Then you'll understand.
 
inertia said:
Download a G-meter app, - that works off the accelerometer chip, not GPS.
Place the G-meter near your tach, - accelerate hard, - when the G-meter drops, you just passed your shift point .
Don't be surprised if the shift point is different in every gear .
Click to expand...

What i phone app did you down load?
 
Stuff like that, I always shift by ear.
If you pay attention, it will tell you almost exactly where it wants shifted at.
I would guess 6k It will get soggy and quit pulling , and right up to that point it will pull and feel crisp
 
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Anyone who has done data recording sees how much time it takes to “see shift light, pull lever, mechanical time for shift to take place”. So keep that in mind when you’re setting the ole shift light!
 
A body said:
Anyone who has done data recording sees how much time it takes to “see shift light, pull lever, mechanical time for shift to take place”. So keep that in mind when you’re setting the ole shift light!
Click to expand...

And the faster the car, the most critical this becomes. YOu'd better be ready for that 1st to 2nd shift or you'll hit the limiter and goodbye ET and win light
 
roccodart440 said:
And the faster the car, the most critical this becomes. YOu'd better be ready for that 1st to 2nd shift or you'll hit the limiter and goodbye ET and win light
Click to expand...
Amen to that!! I still laugh at myself about my 1st pass in the avatar. Not that fast compared to many on here but a 1.51 60-ft time comes in a hurry!! I left the line and the car left so hard it threw me back in the seat and ole dummy's hand was firmly on the shifter and accidentally grabbed 2nd gear in the middle of it leaving. Oops!!

I got a shift light for the next time to the track to keep my big mitt off the shifter and just slap it when the light comes on. This taught me just much I love the Cheetah shifter!!
 
Cheetah is indestructible, but not idiot (me) proof. After losing a bracket race again due to a 1-3-2-3 shift, I took the cheetah out, changed the top plate for a powerglide, and put it in another car. I stuck a pro ratchet in the 62, no more missed shifts, unless I forgot which car I was in (reverse pattern for the 727, forward for the glide). I liked the ratchet so much I bought another, thankfully before they almost doubled in price.
 
Dumped my “Cheetya-out-of-a-round” shifter after it started making the 1-2 shift on its own when I’d launch. PPP was a great investment.
 
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