RPMs?
 

What is a comfortable RPM for an Insert Bearing Engine, and what is the limit you should not exceed?

Re: RPMs?
 

2200 gives you about 50 mph. I would not cruz over 55 & then only if I felt I needed the speed for safety in heavy traffic. 2400 will give you 55 mph if you have 3.78 ratio and 19 inch wheels. Not sure what 21 " wheels will do. But mph x 44 is very close to rpm. Almost exact with 19"

Re: RPMs?
 

This will answer the do not exceed;

https://www.fordbarn.com/forum/showpo...6&postcount=11

Re: RPMs?
 

I have a 3.54 ratio and 16 inch wheels.

Re: RPMs?
 

You can use the Wallace Racing Calculators to work out revs for any given speed if you know rear end ratio and tire diameter.

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

On the sand at Pendine the '29 CCPU in my avatar did 69.87mph at 2411 revs on 21" tires with a 3.27 rear end

Fun with maths. Who knew?

Re: RPMs?
 

2100 - 2200 is a comfortable RPM for cruising, inserts or babbitt.

Re: RPMs?
 

And DON'T lug it, BUT, is PARADE MODE considered LUGGING???
Bill Uncertain

Re: RPMs?
 

My Coupe has a stock Model B engine. The differential is the original 3.78:1 ratio. I regularly cruise this car at 60 mph, and I have had it over 70 mph many many times.

At one time in its life, I had speed equipment (camshaft; Mallory 12V ignition; Holley 94 downdraft, hi-compression head) on the Coupe that enabled some really high speed cruising. The maximum I drove this car was to 85 mph which I held for about 2 miles, and the engine survived. So based on my experiences (approaching 50,000 miles) for a maximum rpm, my guess is at least 4000 rpm with babbitt bearings and synthetic motor oil.

By the way, 85+ mph was a frightening experience with the stock Model A suspension. The motor was still pulling hard at 85 mph, but the car felt unstable so I backed-off and have not gone that fast again.

Re: RPMs?
 

What wheels/tires did you have on it for your 85mph run Bob?

Can then work out your revs using the calculator above

Cheers

Juggs

Re: RPMs?