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09-03-2016, 03:34 PM | #1 |
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Location: Gardiner Me.
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40 pickup stock
Mathematician. Boy, is that a long word. A friend has a 41 pickup, all stock. 3 speed trans. 16in tires. He just installed 3.54 gears, The question for that big math word. What RPM should that stock engine be turning at 60 MPH? I know some of you guy can figure it out. Thanks Walt
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09-03-2016, 03:47 PM | #2 |
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Re: 40 pickup stock
The number I found on line for the tire dia is 28.8". If that is right, the engine would be at 2480 rpm at 60 mph.
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09-03-2016, 04:56 PM | #3 |
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Re: 40 pickup stock
Will your bud need to recalibrate his speedometer after changing gears (guessing from 4:11?), if he stays with the stock size tires?
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09-03-2016, 06:21 PM | #4 |
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Re: 40 pickup stock
Walt, you didn't state what size of 16" tyre.
6.00s = 2548 rpm 6.50s = 2461 rpm 7.00s = 2378 rpm 7.50s = 2302 rpm All at 60 mph with 3.54 gears and 1:1 top gear. I used this (right hand table) http://www.wallaceracing.com/calc-gear-tire-rpm-mph.php 6.00s = 28 in 6.50s = 29 in 7.00s = 30 in 7.50s = 31 in. Mart. |
09-04-2016, 11:03 AM | #5 |
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Re: 40 pickup stock
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09-04-2016, 02:59 PM | #6 |
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Re: 40 pickup stock
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09-04-2016, 10:18 PM | #7 |
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Re: 40 pickup stock
I swapped out the 4:11's in my panel with 3:54's and what a difference that made on the highway. Can be an issue if you are going up hills though.
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09-06-2016, 09:08 AM | #8 |
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Re: 40 pickup stock
If you change the rear gears to 3:54 you should also swap the transmission cluster and main shaft to 29/15. You do not have too but this will help with starting from a dead stop and will be easier on your clutch.
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09-06-2016, 09:21 AM | #9 | |
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Re: 40 pickup stock
Quote:
Walt is it 6 volt? How did you hook up a tach? I was told that a tach on my 6 volt 39 was not possible. With stock ballast resistor / skip coil. Thanks Andy |
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09-06-2016, 06:33 PM | #10 |
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Re: 40 pickup stock
Walt, you tell Ken I will be up and we can see who gets to Ainslies first from your dooryard, I'm bet'n on my 3:54's. Scott
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09-06-2016, 07:51 PM | #11 |
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Re: 40 pickup stock
You can always get one of those cheap digital ones that wrap around a spark plug wire. I have for my motorcycle. It works off a watch battery. Amazon sells them for about $15. Hide it in a spot that only you can see. Bonus is when the motor isn't running, it's a Hobbs meter as well.
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09-06-2016, 10:25 PM | #12 |
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Re: 40 pickup stock
Back in the late sixties, I put a tach on my '53 Customline Coupe, the only change necessary was the bulb to 6V and it seemed reasonably accurate as I recall. Tough to get it over 4000, but it sounded good trying.
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