Rucker overhead valve conversion

fortyfords

fortyfords

Senior Member
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
 
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.
 
fortyfords said:
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
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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.
 
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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.
 
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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.
 
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