Howdy gentlemen,

For a variety of reasons I have no tach capabilities on El Toad at this time and need to decide on which rear to build for her prior to that becoming available.

Presently running a 2.92 with the 904 and able to pin the 110 speedo (a drive check with a known car yields a 2% high readout), squeezing'er fairly tight (BBD & 2 1/4" piped). Don't really need the top end for this car and have a 3.23 available, so can rebuild either one. Homework I've done so far is;

P195/75R14 (92S) on 4 ½ “ rims.

estimated tach for:
mph @2.92 @3.23

60--- 2534-- 2803
70--- 2956-- 3270
80--- 3379-- 3736
90--- 3801-- 4203
100-- 4223-- 4670
110-- 4646-- 5137

This seems a tad off by the feel of it but the p/u tires (selected for their load capacity) appear to be rolling at a bit less than their listed diameter and may account for the deceptive feel.

The freeways I use most commonly tend to run 75 to 85 mph when they're running and Toad feels like she wouldn't mind the 10% tach increase at all. I don't mind the shorter top end and am seriously considering the 3.23, for better hauling as well.

The questions are;
Do these numbers read out by your experiences or will the tach differ significantly when I get one in?
Is a stock drooler capable of being happy long term at 4000 or should I tinker'er up some more?

Thanks for looking.

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Sex, drags, and rock & roll.
Dick, 225% crazy.
Hobby (cars, that is) Photos link

What camshaft are you running?

With a stock cam, I'd go with the 2.93 rear as the power is lower in the rpm range.........

And due to tire bulge, the rolling radius of a tire is smaller than it would be mathematically, so they spin a bit more than you'd expect for the listed diameter......

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

oldsixrodder when i bought my 69 Dart it had a 2.93 rearend in it . But later i put in a 3.23 . This car was a street car and a weekend race car. The 3.23 for me was the better choice. I was driving it to the dragstrip and had not got on it in a while so on the interstate i decided to blow it out before i went racing. I got it up to 110 and it ran out of rpm. That same engine went over 3000 rounds drag racing. With the 3.23 gear in a stock engine it is not going to pull much more than about 5200 rpm. Thanks Ron Parker.

True at low speeds, but centrifugal force causes the tire to "grow" a bit as speed increases. That's one reason our cars often got the best mileage at a steady 30-40 mph. The tires are in effect taller and flex less, but wind resistance hasn't gotten too bad yet.

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"When you find a big kettle of crazy, it's best not to stir it." - Pointy-haired Boss

1964 Valiant V200, 225/Pushbutton 904
BBD, CAI, HEI, LBP, AC, AM/FM/USB, EIEIO

Maybe with bias-ply tires, but radials are very stable in terms of their diameter. When I was supporting a friend doing oval track racing I spoke with a guy that was in a class running radials. He put 80 psi in a tire to try and get some stagger. He got less than 1/4".

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Joshua

Originally I had 2.93's in my Dart.Since I have installed some 3.55's.Shooting around town with these gears is a lot of fun,however highway cruising does suffer a bit.

Many have said that the 3.23 gear is a great all around gear.I think I might have to agree with them here.

JZ

I have 3.23 with 195/75R14 tyres in one of my cars. (stock 225, auto)
I think it is the ideal ratio and wouldnt think of changing.

_________________
Richard (aka Fingers)