The Ford Barn

1929 · 05-07-2016, 05:05 PM

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

sphanna · 05-07-2016, 10:23 PM

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"

Mike V. Florida · 05-07-2016, 11:24 PM

This will answer the do not exceed;

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

1929 · 05-08-2016, 06:08 AM

I have a 3.54 ratio and 16 inch wheels.

Juggler · 05-08-2016, 06:31 AM

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?

Jim Brierley · 05-08-2016, 10:47 AM

Sponsored Links (Register now to hide all advertisements)

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

BILL WILLIAMSON · 05-08-2016, 10:56 AM

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

Bob Bidonde · 05-09-2016, 09:20 AM

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.

Juggler · 05-09-2016, 10:34 AM

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

Y-Blockhead · 05-09-2016, 10:44 AM

A quick calc; With Bob's 3.78's and 30" tire (my guess) he's turning ~3600 RPM.

05-07-2016, 05:05 PM	#1
1929 Senior Member Join Date: Jan 2015 Location: New York Posts: 944	RPMs? What is a comfortable RPM for an Insert Bearing Engine, and what is the limit you should not exceed?

05-07-2016, 10:23 PM	#2
sphanna Senior Member Join Date: Jun 2010 Location: Polk City, Iowa Posts: 526	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" __________________ Steve Hanna, Polk City, IA

05-07-2016, 11:24 PM	#3
Mike V. Florida Senior Member Join Date: May 2010 Location: Florida between Sarasota and TampaSouth Florida Posts: 14,054	Re: RPMs? This will answer the do not exceed; https://www.fordbarn.com/forum/showpo...6&postcount=11 __________________ What's right about America is that although we have a mess of problems, we have great capacity - intellect and resources - to do some thing about them. - Henry Ford II

05-08-2016, 06:08 AM	#4
1929 Senior Member Join Date: Jan 2015 Location: New York Posts: 944	Re: RPMs? I have a 3.54 ratio and 16 inch wheels.

05-08-2016, 06:31 AM	#5
Juggler Senior Member Join Date: Aug 2010 Location: Phoenix AZ/Bath UK Posts: 483	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?

05-08-2016, 10:47 AM	#6
Jim Brierley Senior Member Join Date: Jun 2010 Location: Temecula, CA Posts: 4,251	Re: RPMs? Sponsored Links (Register now to hide all advertisements) 2100 - 2200 is a comfortable RPM for cruising, inserts or babbitt.

05-08-2016, 10:56 AM	#7
BILL WILLIAMSON Senior Member Join Date: Dec 2010 Location: FRESNO, CA Posts: 12,560	Re: RPMs? And DON'T lug it, BUT, is PARADE MODE considered LUGGING??? Bill Uncertain __________________ "THE ASSISTANT GURU OF STUFF"

05-09-2016, 09:20 AM	#8
Bob Bidonde Senior Member Join Date: May 2010 Location: Long Island, NY Posts: 4,112	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. __________________ Bob Bidonde Last edited by Bob Bidonde; 05-09-2016 at 09:26 AM.

05-09-2016, 10:34 AM	#9
Juggler Senior Member Join Date: Aug 2010 Location: Phoenix AZ/Bath UK Posts: 483	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

05-09-2016, 10:44 AM	#10
Y-Blockhead Senior Member Join Date: Jul 2011 Location: Redondo Beach, CA Posts: 6,641	Re: RPMs? A quick calc; With Bob's 3.78's and 30" tire (my guess) he's turning ~3600 RPM.