Quote:
Originally Posted by timsullivan
I'm building a Superformance with most likely a 351W stroker of around 418 or 420 CI that I'm shooting for 450 to 500HP. I will be running 15 inch BFG's or Goodyear GT2's. My rear end ratio is 3.46:1 I am unable to afford changes to the wheel size or tires and don't want to change the rear end ratio. I will be doing occasional freeway driving here in SoCal and occasional longer trips on the freeway but the vast majority of my driving being simply around town.
Which TKO 600 should I get .62 or .82 OD and why in your judgment? Thank you in advance for any input you can give me on this.
-Tim
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Very simple, you know your tire size and rear end gear ratio, you need to "plug in" these numbers into anyone one of the many gear calculators and see what your rpms will be at any given speed......
You also need to know what your engine torque range will be, as stated, don't worry about your peak hp #'s, worry about your engines torque band and try to get your rpms into the torque band..........
I'm running an older Tremec 5 speed in my 65 fastback with the .64 5th gear, 3.25 rear gear and 25.5 inch tall tires, 350hp, 351-W.......I do a lot of highway cruising and a lot of interstate driving in this car... 2000 rpms comes out to right at 75 mph in 5th gear and it's perfect for my motor, I can cruise all day at this level and get 23 mpg........
My cam is a mild camshaft and will run nicely down to about 1500rpms in any gear, so my cruising rpm is perfect for my set-up. If I want to pass someone, I don't have to downshift, just give it more gas and it will accelerate nicely from 2000 rpms.....
With the .64 OD, when shifting from 4th to 5th gear, my rpms drop approx. 900 rpms.......
Your tire/rear gear is known, now you need to determine what rpm level your motor will like to run at and the rpm level your comfortable with at cruising speed........
Just a wild guess, but with a 351-W based stroker, you should have tons of torque and I would think (depending on your camshaft) you could have your cruising rpm level in the 2000 to 2200 rpm range and be fine and still get some decent fuel mileage..........
The only time you'll need 5th gear is on the open road, so don't worry about city driving......
David
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