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 Shift Points and Rear Gear
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421 Bird
Tribal Scout

USA
29 Posts

Posted - 28 Sep 2017 :  4:44:57 PM  Show Profile  Reply with Quote
I fianally was able to make a few passes at the track with my car. As expected, there are some bugs to work out. I keep losing my fan belt at the start, causing over heating. I am guessing there is a pulley that is not in line.

My car has a 421 with a T-10 4 speed, and 3:42 gears. I shifted at 5,300 rpm's. My question is how high can I take the rpm's for my shift points? I was going to take it about 200 rpm higher each run to see what works best, but probably no higher that 6,000 rpm.

My second question is that my car is only at about 3,500- 4,000 rpm's across the finish line. My guess is I need more gear, maybe 3:73 or 3:90. The car is not a daily driver and I am looking for performance over drivability.

Thanks for any input,
Joe

Steve C.
Crazy Horse

1675 Posts

Posted - 28 Sep 2017 :  6:23:43 PM  Show Profile  Reply with Quote
Calculators here will be helpful...

http://www.wallaceracing.com/Calculators.htm

Have you any idea where your engine combination makes peak power, at what rpm. Either by a dyno sheet or based on similar known combinations. It makes no sense to run it out a lot higher than where it does. A extreme example, a engine makes peak power at 5200 rpm and in my opinion it would do no good to shift at 6000 rpm with it.

On my last engine combo it made peak power at 5800 rpm based on the dyno sheet and we just shifted it at 6000 according to the shift light. Knowing that by the time you see the light and make the actual shift it will be slightly higher. Was our method optium ?, I have no idea but it worked out ok. And most important by doing so it was consistent run-to-run. There is also theory where you want the rpm drop down after a shift where the engine is still making torque, or something to that effect, but I never payed much attention. At the time I was using a TH400 transmission, 3.73 gears and 28" rear tires.


.

Edited by - Steve C. on 28 Sep 2017 6:26:06 PM
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tjs44
Cochise

USA
412 Posts

Posted - 29 Sep 2017 :  10:16:47 AM  Show Profile  Reply with Quote
What intake manifold?Tom
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421 Bird
Tribal Scout

USA
29 Posts

Posted - 29 Sep 2017 :  11:57:26 AM  Show Profile  Reply with Quote
The intake is a Performer RPM. Carb is a Holley 750 DP. The motor is bored .20 over with a Crower 60916 cam. Crower states Low RPM at 2,000, Peak HP at 4,800 RPM, and a redline of 6,200 RPM. I shifted around 5,000 RPM the first run, then 5,300 the second run, and ran .39 quicker.
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Blued and Painted
Chief PONTIAC

USA
3407 Posts

Posted - 01 Oct 2017 :  12:14:18 AM  Show Profile  Reply with Quote
Once a used belt flips over once, it will continue to flip.
What type radiator fan.


Bull Nose Formula/ 461/ Q-Jet/
TH400/ 3.08 8.5 / R44TS.
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Steve C.
Crazy Horse

1675 Posts

Posted - 01 Oct 2017 :  02:58:02 AM  Show Profile  Reply with Quote
Most suggest the descriptions listed in cam companies catalogs for power range, redline, etc. is almost meaningless, only a generic guideline. Continue with your trials.

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421 Bird
Tribal Scout

USA
29 Posts

Posted - 01 Oct 2017 :  08:22:53 AM  Show Profile  Reply with Quote
The fan is a Flex-a-lite. I also ordered an alternator for the 1965 engine. I was using the car's original alternator because of the wire connection. I found that the pulley is 2 mm further out from the block. This may be causing the alignment issue.
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Blued and Painted
Chief PONTIAC

USA
3407 Posts

Posted - 01 Oct 2017 :  2:38:29 PM  Show Profile  Reply with Quote
I would not use the hi number gears unless it's a dedicated track car. Even the .373 gets a annoying quick on the highway IMO.
If your car develops more power, the rpm' will be higher at the timers. Leave no stone unturned on the state of tune. Advance curves and total advance can make a big difference in power and drivability. And ovcourse optimum fuel mixture.
Weight reduction is another option.
Also any wheel spin will raise elapse time.


Bull Nose Formula/ 461/ Q-Jet/
TH400/ 3.08 8.5 / R44TS.
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421 Bird
Tribal Scout

USA
29 Posts

Posted - 01 Oct 2017 :  11:41:21 PM  Show Profile  Reply with Quote
Thanks for the advice. I think the timing may be my next point of focus. I feel the timing may be a little too advanced, as the motor seems to run cool. It starts easily, and there is no ping.
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421 Bird
Tribal Scout

USA
29 Posts

Posted - 09 Oct 2017 :  1:53:05 PM  Show Profile  Reply with Quote
I had someone look at the car this past weekend. He ended up putting in bigger jets and squirters, as it was not getting enough fuel. He also set the timing. The motor seems to be running alot better now.
I also changed the alternator, and the pulleys line up alot better.
I am hoping to get the car to the track and see how it performs.
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4spta
Tribal Scout

USA
20 Posts

Posted - 15 Oct 2017 :  9:18:04 PM  Show Profile  Reply with Quote
Any Updates??

400/467cu.310cfm kauffman D-ports w/1.65 steel roller rocker arms. XE274-H cam.Forged steel Ohio crank.Eagle rods. Icon pistons.Balanced.HSD intake.750mech.sec Holley.1-3/4in hedders.3 in collectors.2-1/2in exhaust.Flowmasters.ST-10 tranny.4.10 gears. 6 point cage.subframe connectors.every bushing polyurethane. F/R drag shocks line lock. Lightened up front end. Appox.3500lbs

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421 Bird
Tribal Scout

USA
29 Posts

Posted - 16 Oct 2017 :  4:18:43 PM  Show Profile  Reply with Quote
Unfortunately, my local track had a big 3 day race weekend, and there was no test and tune. This was also the last weekend that they are running this year. There is another track about an hour away. I am going to try to get there before the season is over. I did get the car on some open road and it is definitely pulling harder through third gear. The RPM's went up about twice as fast as before. I didnt run it through fourth gear. It seems like the lack of fuel was really hurting the performance. I will let you know if I make it out to the track.
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