Question on higher rpm gains

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pittsburghracer

pittsburghracer

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What did you actually see on the track with shifting at slightly higher rpm. I’m not talking over 7500 but say from 6800-7200rpm. I usually baby my stuff as it’s just a bracket car but we all know guys always like to go faster. I’m not much of a test and tuner as I’d rather take my one or two hits on race day and get out the shoe polish. But man this new 408 is really pulling at the 6800 rpm shift. With a roller cam and .650 lift she sure sounds nicer than my 422 with a .650 solid lifter cam and Indy heads. Please post up your findings.
 
John, did you have the engine dyno’d?
 
528 megablock 4.5 bore 4.15 stroke crank diamond 0 deck pistons Stage 6 Max wedge heads done by Duane Porter 950 Holley HP 308R solid roller comp cam MW M1 intake.

20220613_184640.jpg
 
My combo's have not been at the level of power that you are making. I have played many shift point games and I've always seen there is a sweet spot where +/- 200 rpms doesn't change the MPH or ET. I always shift at the lowest RPM that still makes the best ET. In other words, if 5600 will run the same ET/MPH as 5800, I'm shifting at 5600.
 
318willrun said:
My combo's have not been at the level of power that you are making. I have played many shift point games and I've always seen there is a sweet spot where +/- 200 rpms doesn't change the MPH or ET. I always shift at the lowest RPM that still makes the best ET. In other words, if 5600 will run the same ET/MPH as 5800, I'm shifting at 5600.
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Sounds safe!
 
318willrun said:
My combo's have not been at the level of power that you are making. I have played many shift point games and I've always seen there is a sweet spot where +/- 200 rpms doesn't change the MPH or ET. I always shift at the lowest RPM that still makes the best ET. In other words, if 5600 will run the same ET/MPH as 5800, I'm shifting at 5600.
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I planned on rebuilding my old 422 after three years and it didn’t happen so I lowered shift rpm from 7000 to 6800. On the 5th year I lowered it to 6700 and it still ran 6.0’s. But again it was a solid lifter cam engine.
 
I've always leaned towards short shifting out of first , second and third when it stops pulling and wind it out in 4th. But you want to go through the trap at a little higher than peak hp. At least that's what I did with other lower hp cars. Could get the same mph but slower ets
 
66Valiant528 said:
I've always leaned towards short shifting out of first , second and third when it stops pulling and wind it out in 4th. But you want to go through the trap at a little higher than peak hp. At least that's what I did with other lower hp cars. Could get the same mph but slower ets
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I only have the one, two shift to worry about. (Powerglide)
 
There’s only a couple ways to find out. Make a bunch of test and tune runs shifting at different rpm (which you said you’re not privy to) or put it on a chassis dyno and find where it makes peak hp. Then you can narrow down your shift rpm.
On your powerglide, how many rpm does it drop on the 1-2 shift?
 
A cheap dash cam pointing at the tach is what I evaluate with the timeslip. Pay attention to the rpm drop of the shift and how quickly the motor recovers to make your decision.
 
Just my opinion...Unless there is some benchmark you'd want to hit, like a 6.01 to a 5.99, i wouldn't fool with it myself. Probably only talking a few hun in the 1/8th anyway. If she's consistent for now, why push it.

By the way, your car runs fantastic. :thumbsup:
 
mderoy340 said:
A cheap dash cam pointing at the tach is what I evaluate with the timeslip. Pay attention to the rpm drop of the shift and how quickly the motor recovers to make your decision.
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No tack as I have a race pak dash but I just hopefully got my egt’s working so I can tell exactly what the rpm drop is when I load my SD card. I bought a go-pro many many years ago and never used the dog gone thing.
 
If i recall correctly, you went to a 1.80 1st with this combo. Do you think going back to the 2+ first would get you into the lower range of the power band faster? Just curious, you'd know better then i would. :)

My thought process on this was it may bump your 330' a bit and add a few rpm's at the top?
 
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With the Glide and your combo I do not think more than several hundreds from
that amount of change and you camshaft.

In nornal mode our SS/KA (3400lbs.))Duster shifting Auto @ 6500 and 6800 = 10.2s

In Heads up mode 7400 and 7600 (plus 0 Wt.Oil ) =9.9s
But our camshaft is .750+ and only 10:1 Compression with 904 3 Speed and Iron 308 Heads.

As the RPMS increase expect more Valve Train maintenance.
 
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My 440” W2 engine made peak power at 6900 rpm. Shifted at 7200 rpm.
660 lift roller, tunnel ram, 13.1 compression.

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OldmanRick said:
If i recall correctly, you went to a 1.80 1st with this combo. Do you think going back to the 2+ first would get you into the lower range of the power band faster? Just curious, you'd know better then i would. :)

My thought process on this was it may bump your 330' a bit and add a few rpm's at the top?
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Different engine combo but basically the same ET my old 422 would sixty foot at 1.32-1.33 with a stock 1.76 low gear. With the 1.98 a 1.25 was the best sixty foot but usually around 1.27 but the 1/8 mile ET was the same with both gears. Now with the new 1.80 it’s 1.30-1.31 and a much calmer leave.
 
OldmanRick said:
Gotcha. Sounds good. Thank you for responding.
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My 367 made peak horsepower at 6500 on the dyno and started to fall off after that so I shift at 6500 , actually I am shifting at 6,000 right now as another way of slowing the car down for 11.50. That 500 rpm equals about a tenth in my combo. When I ran this motor on race gas ( now lower compression and pump gas ) I had a 4.88 gear in the car I still have my stroker motor gears in now 4.30s. I will be switching back to 4.88s soon. I have always launched at 2,500 a few years ago when my friend was driving my car he was leaving at 2,000 and I found no difference in 60 fts. between 2,000 and 2,500 so I now leave at 2,000 via footbrake. This motor made 527 hp and 467 tq on the dyno its gone 11.00s at 119 recent changes should put it in the 10.90s but it is throttle stopped down for 11.50s

E0BA0428-96CD-470F-9AEA-2074FE426DAA.jpeg
 
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A very well balanced engine will keep on spinning up. A Engine not well balanced will come apart quickly.
416, Indy 360-1 heads. 686 roller. 2" tubes. 12.5-1. Heavy steel crank and rods. 829@7900. Best times were achieved a 8000 shift. Shift light set at 7800. Car was heavy. @ 3850 with 200 lb. driver.

You can tell the difference on a solid mount run stand when they are Balanced within 2 grams they are Very smooth. Harmonics will kill an engine.

The last Low mileage stock 340 on the stand you could feel was not balanced. That is the way some were. If your engine is is solid mounted in the car and you can feel it in the chassis holding it a 4000 just shift it where it can handle it. Like I said bad harmonics is what kills engines. Balancing is critical. After starting so many engines you can feel the few built by others that were not balanced.









 
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