Cruise RPM?
 

New to me: 47 Ford business coupe. It has 59AB with Offy heads,Offy intake 2 97's carbs, Isky 400 cam stock 3 speed trans. As far as I can tell stock rear diff. What would be a comfortable RPM on highway speed say 60-65?

Re: Cruise RPM?
 

Need differential ratio and tire dia to give any meaningful figure.
( other than that 2500 ±)

Re: Cruise RPM?
 

"Comfortable cruise RPM" is what it is regardless of other factors. My '38 has a 3.78 rear and 29" tires. 60 MPH is about 2700 rpm and the car and I am comfortable there.

Re: Cruise RPM?
 

I have 3.55's and 2.25/75R15 rear tires in my '51 club coupe with a '51 Merc with a stock cam, no overdrive. I find that 2700 RPM is the maximum comfortable cruise speed. On my car, that's about 70 MPH. I find these engines like to run at 2300-2700 RPM.

Re: Cruise RPM?
 

R.P.M. equals, MPH times gear ratio, times 336, divided by the tire diameter. That will tell you what you have now.

Re: Cruise RPM?
 

Well, assuming that 6.00 16 Cokers are 29" diameter ?, I did the math posted by woodiewagon46. My '38 Conv Cpe purrs at 70 mph, to my ears sounds and feels better than at 65. I have 3.78 gears, which puts my rpm at 3066. My engine is a 59L, built in 1963 by the former owner. I have no idea what the internals are, but it does max out at about 86 on the Nevada desert, which would be 3766 rpm at that tire diameter.

Re: Cruise RPM?
 

I try to stay below 2700

Re: Cruise RPM?
 

My Deuce roadster has a Ford 8" rear with 2.89 gears. I cruise down the Jersey or PA Turnpike at 70 MPH at about 2400 RPMs. I have a friend that's building a street rod with over 800 HP and 4.56 gears and monster Mickey Thompson's in the rear. He told me he can't wait to drive to the Nat's in Louisville. I don't think he has any idea what that is going to be like. Back to your situation, the only thing you can do is change the gears, which is a major job or tires, 3766 RPM's is a lot for a flathead. As most have suggested between 2300 and 2700 is a nice cruising RPM.

Re: Cruise RPM?
 

Here's a good link to rpm, tire size, differential ratio and speed.
http://www.advanced-ev.com/Calculators/TireSize/

Re: Cruise RPM?
 

Run WIDE OPEN. It's a Ford.

Re: Cruise RPM?
 

The above mirrors my 39 coupe tyre wise and rpm. Runs well at 70 mph.
Our speed limit here in NZ on open road is 100 kph. Usually run at 60 to 65 mph will run here sweet all day.
Phil NZ

Re: Cruise RPM?
 

Between 2000/2500 rpm air/fuel ratio in the low 15.
Gramps

Re: Cruise RPM?
 

Yeah, it's a Ford engine that exploded around itself while racing, or what's left of it, anyway! DD


https://www.fordbarn.com/forum/attac...7&d=1646423346

Re: Cruise RPM?
 

What did that busted engine start out as?

Re: Cruise RPM?
 

I saved that almost unbelievable picture years ago. I can't remember ANY details now, except that it was some sort of Ford race engine.

That picture is almost as good as the two pics below of the engine in the "Magic Muffler" Fiat at Lyons one night with Gary Essman driving. That crankshaft ended-up in another engine at a later date. DD

https://www.fordbarn.com/forum/attac...2&d=1646432752

https://www.fordbarn.com/forum/attac...1&d=1646432578
.

Re: Cruise RPM?
 

I,ve raced at Lions drag strip in S. Cal. Is that Lyons? I also used to work at San Fernando drag strip!

Re: Cruise RPM?
 

I don't know what it is either, but I would hit the buy again button on the cam manufacturer.

Re: Cruise RPM?
 

I once broke down on Sunset Blvd. one New Years eve in front of the Graumans Chinese theater. I had a box of pistons in the trunk from some other work and spread them out behind my car till I got it going. Lots of laughs that night!

Re: Cruise RPM?
 

That second picture is not a good commentary on "C&T Strokers".

Re: Cruise RPM?
 

The funny thing about the Magic Muffler Fiat car. is the guy sitting in the drivers seat was actually the engine builder, and the first time behind the wheel. What you see is when someone forgot to torque the main caps