Two more questions

[414TATA]

Just wondering what the RPMs are on the straight 8 (1941) at 55 - 60 Miles per hour?

Also asking about the shifting speed. I have been in 1st on (level road) to about 15 mph. In 2nd gear to about 25 - 30 mph. Is this about right? It feels okay to me. I just don't want to push the "Old Girl" too hard in 2nd, But you know what the traffic behind you is like. They are all so impatient. ha.

Thanks for the help

Wayne B.

1941 Buick Super 50

Fresno, Ca.

[Guest Grant Magrath]

Sounds about right.

I think there's a thread on here somewhere discussing the rpm at highway speeds. Use Search and see if you can track it down, I think it was fairly recent!Cheers

Grant

[Guest BJM]

Don't ever worry about modern traffic. That is their issue not yours. Modern cars (as you probably know) are set up for jack rabbit starts.

[Grandpa]

Hi Wayne,

The 1941 Buick Super had two rear axle ratios:

Standard = 4.1 to 1

Optional = 3.9 to 1

If your car has the 4.1 ratio, you may want to change it to 3.9 ratio or lower, in order to keep the rpms down at freeway speed. The gear ratio can be checked by removing the rear end cover - the number of teeth, both ring & pinion, should be stamped on the edge of the ring gear (or) by removing the speedometer drive gear and counting the teeth on the gear and checking with the parts book.

Grandpa

[414TATA]

Thanks for the response. I did a search for RPM no luck. If anyone would take a guess at the RPM at 55-60 mph as I don't have a clue on this straight 8. I think I probably have the standard 4.1 axle ratio. 60 mph is pretty much the limit for me on highway / freeway.

Thanks again

Wayne

[Grandpa]

Hi Wayne,

To obtain engine rpm -

• Measure the diameter of your tire in inches

• Multiple the diameter by 3.14159 to obtain the tire circumference in inches

• Convert the above tire circumference to feet by dividing by 12

• 60 mph is 5280 feet per minute

• Divide 5280 by the tire circumference to obtain wheel revolutions per mile

• Multiple the wheel revolutions by the axle ratio (assume 4.1) to obtain engine rpm

Grandpa

[nzcarnerd]

Modern cars may be set up for jack rabbit starts but they also have tall overdrive gears that allow them to loaf along at less than 2000rpm at highway speeds. You will find that at 60mph your Buick will be doing around 3,000rpm which is plenty fast enough for it to maintain - especially if it still has its original rod bearings and oiling system.

[414TATA]

Hi Wayne,

To obtain engine rpm -

• Measure the diameter of your tire in inches

• Multiple the diameter by 3.14159 to obtain the tire circumference in inches

• Convert the above tire circumference to feet by dividing by 12

• 60 mph is 5280 feet per minute

• Divide 5280 by the tire circumference to obtain wheel revolutions per mile

• Multiple the wheel revolutions by the axle ratio (assume 4.1) to obtain engine rpm

Grandpa

Thanks again you are a huge help here for me as I am new to this. I'm Sure having fun.

I will save this info.

Wayne

[414TATA]

:

Modern cars may be set up for jack rabbit starts but they also have tall overdrive gears that allow them to loaf along at less than 2000rpm at highway speeds. You will find that at 60mph your Buick will be doing around 3,000rpm which is plenty fast enough for it to maintain - especially if it still has its original rod bearings and oiling system.

Thanks for the good advice. I do have all original engine. I plan to keep my max. speed in the under 60 mph range.

Wayne

Fresno, Ca.

[Barney Eaton]

I have a '39 Century with 16" tires and a 3.90 final drive. Using a dwell meter with tach function, I tested mine soon after the purchase and as I recall it was 20 mph = 1000 rpm roughly (60 mph was 3000 rpm) in high gear.