[strummin67]

I have a '64 Nova wagon with a 194 6 and the stock 3:36 rear gears. It originally had a three speed on the column. I have since replaced it with a BW 5 speed from an S-10 pickup and replaced the 13/80-185 tires with 14/205-70s. The four gears are a definite improvement over the three but the gear spacing could be better and I am unable to use the 5th (overdrive) without losing gas mileage. Kind of defeats the purpose. Anyway, I see two options:
1. Replace the rear gears with numerically lower gears (3:08). Benefits- lower RPMs on the freeway, increase in mileage ( I hope). Drawback- still no use for the 5th gear.
2. Replace the rear gears with a numerically higher gears (3:55-3:73). Benefits- I most likely can use the 5th gear. Drawback- 1st gear is 3:76 and short already so I most likely won't need it unless I start pulling stumps. The whole reason I made the swap was to possibly improve the 20 mpg I already get on the freways. I am now wishing I had just gone with a Saginaw 4 speed. It would have been cheaper. What do you guys think?

Strummin

[Deuce]

You are higher geared ( effectively ) with the 14 inch tires ... over the 13's. A 3.08 will make it worse IMHO. You need to go the other way ... and gear it down so when you use 5th gear ... it will be a little LOWER RPM wise with the 14's than it was with 13's and the 3.36 ... IMHO

Also mileage comparisons now to the past are not accurate unless you corrected the speedometer ... because the odometer will be off. With the 14's ... you have went further that the odometer shows ...

[spinn]

usually thats why i dont believe anyone sayin theryre hotrod gets 20 mpg ! speedometer gearing error.

if you have a big engine with a cam, i think its all going out the tailpipe

[strummin67]

20mpg was driving conservatively back from a 220 mile trip to Reno on the stock engine and and original 3 speed tranny. I now need to find my engine's "happy zone" where it's able to work efficiently and not scream at 3250 while doing it.

Strummin

[strummin67]

...And yes the odometer is off. After I replaced the tranny I had my wife pace me in her car. When she was doing 65mph I was showing 61mph. I have an RPM/Gearing calculator that says with my current combination I should be running at 2900rpm at 65mph. This is a 6 not a V8 so I'm learning that there are a different set of rules to follow.

Strummin