Took the 460 and C-6 out of the F100 and replaced it with a 351-W and C-6 and the speedo is 5 too slow,I thought I was told each tooth of the gear is good for 3 MPH so I was thinking 2 less teeth and if I can get 1 fast or slow it will be close enough to me so is that right. The last time I corrected it when it was slow I went from 2.75 to 3.00 gears and it was 1 fast but the 3.00 gears are staying and would like to change the speedo gear only this time..
how is the odometer? The amount adding/subtracting a tooth will affect it depends on how many teeth it has...it's a percentage, you know
well....usually the speedo is not quite calibrated right, relative to the odometer. I like to get the odometer right by adjusting the gears in the trans, then fiddle with the speedo spring and needle position to get it to read correctly relative to the odometer. but I play with this stuff way too much
I ran a dyno at a couple of Ford dealers. Generally, I found that 1 tooth chang in the driven gear was worth 2 1/2 mph. I used to love when calibrated their speedo after they got a ticket. I'll show this to the judge and get out of the ticket was their usual statement. To which I would reply, I don't think so, usually the judge would say something like "congratulations, now you shouldn't get another speeding ticket, pay the clerk".
I will pull the cable tomorrow and count the teeth and see if I have one with two less teeth and if I do not see if a dealer can get me one.
My brother is into King Midgets, and during his efforts to calibrate his speedo to his modified drivetrain, came upon some information stating that most speedometers are calibrated to read 60 mph at 1000 rpm, that being speedometer drive cable rpm. In the late '60's, the new owner of the King Midget Corp. decided to certify the cars for a 50 mph cruising (lol) speed, so they could be run legally on the Pensylvania Turnpike, among other roads with minimum speeds. His first trip into PA resulted in a ticket for failure to maintain that speed, even though his newly "calibrated" speedometer indicated he was.
yes indeed, 1000 revs of the speedo cable per mile is a rather standard number. I just assume that everyone knows that...thanks for mentioning it.
It had a 19 tooth gear and I had a 16 tooth gear and according to digital the your speed is sign its right on.