'54 tach rev counter

[Leif A.]

A friend recently purchased a '54 and was thinking the 67k miles may be original. If we assume that the tach rev counter has been functional from day one, what is the mathematical formula to find mileage using the numbers on the rev counter?

[Jim L.]

Re: '54 tach rev counter

There isn't an exact correlation between the rev counter and the odometer. This is because the rev counter continues to run when the car is not moving at all and because, with the PowerGlide there is always some unknowable amount of slippage.

However......

If the tires rotate 750 revolutions/mile and if the differential gears are 3.55:1, then the rev counter would record approximately 2662 revolutions/mile. For a 67k mile car, the rev counter should indicate a minimum of 178380 thousands of revolutions.

Jim

[Leif A.]

Re: '54 tach rev counter

There isn't an exact correlation between the rev counter and the odometer. This is because the rev counter continues to run when the car is not moving at all and because, with the PowerGlide there is always some unknowable amount of slippage.

However......

If the tires rotate 750 revolutions/mile and if the differential gears are 3.55:1, then the rev counter would record approximately 2662 revolutions/mile. For a 67k mile car, the rev counter should indicate a minimum of 178380 thousands of revolutions.

Jim

Jim,

Thanks so much. I hadn't thought about the car sitting at idle...valid point. I appreciate your way to calculate the mileage...even knowing that it won't be exact, it will give him some idea.

[Troy P.]

Re: '54 tach rev counter

I did a study on this a few years back using mileage and revs on 8 unrestored cars. The average was 3250 revs per mile. That accounts for real life driving conditions including idle.

[Leif A.]

Re: '54 tach rev counter

I did a study on this a few years back using mileage and revs on 8 unrestored cars. The average was 3250 revs per mile. That accounts for real life driving conditions including idle.

Troy,

Thank you for your response. I will pass this information onto my friend.