I was wondering what gear ratio you guys think would work best for my project. I'm building a 32 Ford with 49-53 flathead (stock horsepower) and a 39 Ford trans. I have a Halibrand Quick change rear with the option of any gear ratio (with in reason). I plan on using an open drive set up. I was thinking 3.08/3.25 and I didn't know if that would be too much/not enough? thanks guys.
That would seem to be right in the range for general good performance and reasonable highway rpm...........without knowing more specifics as to tire size, full fendered or open wheel (wind resistance at speed), and what kind of driving you do most. But since you have a quick change.........no problem....eh? Ray
sounds pretty good...what diameter tire are you running and you gonna be interstate or town drivin mostly?
If your running around a 30" or so rear tire you might find the 3.08 a little hard to pull in high gear, especialy in hilly country. I'd go closer to the 3.25 in that case. Remember stock flatheads were geared anywhere from 3.54 to 4.11. Frank
Virtually all production passenger cars from early on through at least the late '50s were geared rather low (high numerically), mostly because of the roads of the day and the need to pull well at moderate speeds. Vehicle weight is also a factor. A given engine/tranny/axle ratio in a heavier car isn't necessarily right for a lighter car. Reducing weight has the same effect as adding torque to the engine when accelerating or maintaining highway cruise up hill and down. Also, many cars of the 50's with the lowest gears (4.10 or so) were equipped with overdrive. My '40 Buick Super has 4.40s...........they are coming out of there...and very soon. Ray
if you have an idea where your power band is the attached spreadsheet might help, i made this up a while back to help my dad with the same challenge on his 61 409 powered Impala SS.... The HP line was just some numbers i plugged in from a dyno run to show the power band....might be a bit optimistic to use that curve for the Flatty....but ya never know
I'm running a 3:27 gear in a 31 PU with a 239" flattie. I think the 3:05 gear would be to much for your engine. Your power band will start just above idle with a stock cam. Butch
I am running a 3.12 in my quicky with 8BA and love it it still pulls good enough in low and is great at 70-75 cruising I tried a 3.48 but it seemed a bit much to cruise at 75 with
The QC was not designed for race vs. mileage, but for changing track conditions where the ratios would be close together. No point in having a QC with ratios only 6% apart for street - you won't even notice the difference. At 60 mph with 30" tire, it's 2,070 with the 3.08 and 2,184 with the 3.25. You want at least 3.55 with a 30" tire for traffic, and at least 20% lower RPM for the other ratio for cruising, like 2.80.
The good news is.......if you choose a bad ratio, it will only cost the price of a new set of spur gears $ 50. to $ 75., 2 quarts of gear oil and about 10 min. to correct ! Dave
Hey thanks guys. I plan on running 7.50X16 in the rear and 5.50 or 6.50 in front. It sounds like either gear set will work.
I'm runnning a 239 flathead 6 in my poncho with 3:42 gears on 205-75-15's. Cruising at 55-60 I'm spinning about 1700 - just where it loves to run. My 2 cents
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