The Ford Barn

fortyfords · 11-29-2023, 06:56 PM

What would be a good rear end ratio to run over the high cost of a Mitchell overdrive unit. This Rucker runs two Stromberg carbs and headers. Don't know anything else about the engine but it sounds healthy. It's in a stock 30 Model A coupe. For instance, would 3:00's be too tall or would a lower 3:50 ratio be better? I hope this is enough information and if anyone has experience with Rucker setups, I would appreciate hearing from you. Thanks for any help

ModelA29 · 11-29-2023, 07:32 PM

Nobody makes a 3.0. There are ones that are about 3.25 and about 3.50. I'd run the 3.25s. You'll also want to change the speedo gears to keep it reading close.
The common 3.78 becomes a 2.8 with the 26% Mitchell. I've driven ours with the Mitchell in high around town. It doesn't accelerate as well but our AER touring engine has enough guts to pull it along just fine.

Y-Blockhead · 11-29-2023, 07:43 PM

Quote:

Originally Posted by fortyfords

What would be a good rear end ratio to run over the high cost of a Mitchell overdrive unit. This Rucker runs two Stromberg carbs and headers. Don't know anything else about the engine but it sounds healthy. It's in a stock 30 Model A coupe. For instance, would 3:00's be too tall or would a lower 3:50 ratio be better? I hope this is enough information and if anyone has experience with Rucker setups, I would appreciate hearing from you. Thanks for any help

One of the main issues I see running taller rear gears over the Mitchell is the rather large ratio gap between 2nd and 3rd gear in the stock transmission.

With the Mitchell, you can use it as a gear splitter and close this gap.

fortyfords · 11-30-2023, 07:20 AM

That is great information from people who know, Thank you both so much.

Jim Brierley · 11-30-2023, 11:21 AM

It also depends on what the terrain is where you live. I ran 3.27's in my speedster for awhile, they were great on the highway but not so good from a stop. My solution was a quick rear end, not what everybody'd like. The Rucker, or any OHV will want to cruise at the speed any A would. A good cruising RPM is usually about 2,000 RPM for most engines.

Cartravel · 12-11-2023, 11:23 AM

Sponsored Links (Register now to hide all advertisements)

The overheads I've seen do not provide much change in torque. Since they breath better, the torque is extended to higher rpm before it falls off, so the peak hp is greater. If you use a taller rear end you're likely to lose some low end acceleration and hill climbing. This observation assumes you're not also increasing compression.

11-29-2023, 06:56 PM	#1
fortyfords Senior Member Join Date: Mar 2011 Location: faucett, mo Posts: 419	Rucker overhead valve conversion What would be a good rear end ratio to run over the high cost of a Mitchell overdrive unit. This Rucker runs two Stromberg carbs and headers. Don't know anything else about the engine but it sounds healthy. It's in a stock 30 Model A coupe. For instance, would 3:00's be too tall or would a lower 3:50 ratio be better? I hope this is enough information and if anyone has experience with Rucker setups, I would appreciate hearing from you. Thanks for any help

11-29-2023, 07:32 PM	#2
ModelA29 Senior Member Join Date: Sep 2022 Location: SoCal Posts: 591	Re: Rucker overhead valve conversion Nobody makes a 3.0. There are ones that are about 3.25 and about 3.50. I'd run the 3.25s. You'll also want to change the speedo gears to keep it reading close. The common 3.78 becomes a 2.8 with the 26% Mitchell. I've driven ours with the Mitchell in high around town. It doesn't accelerate as well but our AER touring engine has enough guts to pull it along just fine.

11-30-2023, 07:20 AM	#4
fortyfords Senior Member Join Date: Mar 2011 Location: faucett, mo Posts: 419	Re: Rucker overhead valve conversion That is great information from people who know, Thank you both so much.

11-30-2023, 11:21 AM	#5
Jim Brierley Senior Member Join Date: Jun 2010 Location: Temecula, CA Posts: 4,089	Re: Rucker overhead valve conversion It also depends on what the terrain is where you live. I ran 3.27's in my speedster for awhile, they were great on the highway but not so good from a stop. My solution was a quick rear end, not what everybody'd like. The Rucker, or any OHV will want to cruise at the speed any A would. A good cruising RPM is usually about 2,000 RPM for most engines. Last edited by Jim Brierley; 11-30-2023 at 11:24 AM. Reason: Added info

12-11-2023, 11:23 AM	#6
Cartravel Senior Member Join Date: May 2010 Location: Larry Young, Tulsa, OK Posts: 202	Re: Rucker overhead valve conversion Sponsored Links (Register now to hide all advertisements) The overheads I've seen do not provide much change in torque. Since they breath better, the torque is extended to higher rpm before it falls off, so the peak hp is greater. If you use a taller rear end you're likely to lose some low end acceleration and hill climbing. This observation assumes you're not also increasing compression.