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#1
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455 Shift Point
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 |
#2
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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.
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Mick Batson 1967 original owner Tyro Blue/black top 4-speed HO GTO with all the original parts stored safely away -- 1965 2+2 survivor AC auto -- 1965 Catalina Safari Wagon. |
#3
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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. |
The Following User Says Thank You to Half-Inch Stud For This Useful Post: | ||
#4
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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. |
#5
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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!
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'73 T/A (clone). Low budget stock headed 8.3:1 455, 222/242 116lsa .443/.435 cam. FAST Sportsman EFI, 315rwhp/385rwtq on 87 octane. 13.12 @103.2, 1.91 60'. '67 Firebird [sold], ; 11.27 @ 119.61, 7.167 @ 96.07, with UD 280/280 (108LSA/ 109 ICL)solid cam. [1.537, 7.233 @93.61, 11.46 @ 115.4 w/ old UD 288/296 108 hydraulic cam] Feb '05 HPP, home-ported "16" D-ports, dished pistons (pump gas only), 3.42 gears, 275/60 DR's, 750DP, T2, full exhaust |
The Following User Says Thank You to Lee For This Useful Post: | ||
#6
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Great advice, Lee!
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Regards, "455HO" Lloyd 2008 GMC Sierra Denali 2WD Crew, L92 6L80E, Silver w/ Ebony guts, 14.26 @ 98 |
#7
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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.
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The Following User Says Thank You to ta man For This Useful Post: | ||
#8
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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
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'78 Macho T/A DKM#95, 460cid, SRP pistons, KRE 310 D ports, 3" pypes, Hooker 1 3/4" headers, hydraulic roller, 10" Continental, 3.42 gears 11.5 @117.5mph 3900lbs ([_|_] ##\|/##[_|_]) |
#9
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Quote:
Lee
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'73 T/A (clone). Low budget stock headed 8.3:1 455, 222/242 116lsa .443/.435 cam. FAST Sportsman EFI, 315rwhp/385rwtq on 87 octane. 13.12 @103.2, 1.91 60'. '67 Firebird [sold], ; 11.27 @ 119.61, 7.167 @ 96.07, with UD 280/280 (108LSA/ 109 ICL)solid cam. [1.537, 7.233 @93.61, 11.46 @ 115.4 w/ old UD 288/296 108 hydraulic cam] Feb '05 HPP, home-ported "16" D-ports, dished pistons (pump gas only), 3.42 gears, 275/60 DR's, 750DP, T2, full exhaust |
#10
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My thanks to everyone. I'll pull the shift point back down some.
Mack |
#11
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Quote:
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. |
#12
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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.
__________________
Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
The Following 2 Users Say Thank You to steve25 For This Useful Post: | ||
#13
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there is no way you want to shift at peak torque rpm if your goal is to maximize acceleration?
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#14
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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.
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#15
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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.
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Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
#16
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"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?
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If you can read this, thank a teacher. If you can read this in English, thank a Veteran! https://cliffshighperformance.com/ 73 Ventura, SOLD 455, 3740lbs, 11.30's at 120mph, 1977 Pontiac Q-jet, HO intake, HEI, 10" converter, 3.42 gears, DOT's, 7.20's at 96mph and still WAY under the roll bar rule. Best ET to date 7.18 at 97MPH (1/8th mile), |
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