Thread: Best gear ratio??

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Currently building a 37 glass body 37 Ford coupe using a EFI sb Chevy with about 350+hp, 700r4, 8" posi, running big 275/45/20s on the rear (29.75" diam). I want to be able to smoke em if I feel like it but don't want to buzz the motor too much at a 75mph cruise. Any recommendations?

I had a 3.0 gear in my 32 Ford, and was able to cruise the hwy comfortably at 65. When the need arose, the tires would bake. I had a 468 BBC, and clicked off a 10.93 at the nostalgia drags. I got the best of both worlds by being able to cruise the streets getting 12mpg, and goin fast on race day.

With that tall a tire I'd say a 3.50, no less than a 3.25. You've got an OD trans too so you aren't going to be too buzzy.

Definitely no more than a 3:55. That way you can have both good crusing mileage and on those occasions when you want to smoke them you can.

I am looking at the same options, my choices are either a 3.55 or 3.80 gear for my 8 inch. With the 700R4, you will have a ball in 1st and 2nd gear, then be able to cruise at 2000 or less at 65 in OD.

Pat

BTW, here's a chart for the various ratios available for the 8" that calculates RPM. For your size tire you'll either have to extrapolate, or use the formula provided.

http://www.metropartsmarket.com/rearend/ratio.html

Streets:

Although I am still the "new guy", my first posting got a reply from you estimating 18 mpg (max) in your "pail" with a 2.79:1 rear and a 383 SBC. Here you mention 10-19 mpg with a 358. Can you tell me/us what cam you are running in the 358 and the intake. I probably have seen your "pail" in Street Rodder at some time or other or perhaps some other "pail", the point being that the weight is about what, 1600 pounds? As you know I have been chasing my tail trying to figure out how to get 20 mpg or more from a rebuilt 350 with TH350 and 2.79:1 Maverick rear, the same ratio you quote. Since a hot rod is supposed to be "hot", I really don't want to go to high pressure tires, two bbl carb and vacuum gauge, just a reasonable way to get 20 mpg. Now you mention 19 mpg so I would like to know your cam at least. Also while you are on the air what do you remember about the Edelbrock Streetmaster intake which Vic Sr. offered to provide low speed torque and mileage during the gas crisis of 1974. I am trying to keep up and today I replaced some of the bolts in the four-bar with longer bolts and installed the cross-over steering and the Vega-box, so I am getting closer to the time when I have to pin down the specs on my crate engine order.

Don Shillady
Retired Scientist/teen rodder