My gear shop that is doing my posi and gears in the 12 bolt is recommending 343s saying that with the massive amount of torque with a big block there is not that much difference and the car is more streetable and will still give you the seat of the pants feel.

This car will not be driven daily, maybe 10 mile drives at most and possible a 30 miler once a month and currently has 245/60/15 in the rear at the moment.

Engine setup below

396 .30 over
10.5:1 TRW forged pistons
Forged steel crank
Voodoo 268 cam (60203 227/233@.050 .542/554 lift 110 LSA)
Oval port 290 heads with minor port work
2.19/1.84 valves
1.7 Aluminum roller rockers
RPM Air Gap manifold
Speed Demon 750 carb vacuum secondary
TH350 w/shift kit
10" ATI converter


thanks for the help.

Tim

Tim,
I would probably be inclined to agree with them, but its your car ..... do it the way you want. I figured out with your tire size at 60mph with the 373 gears you would be turning a little over 2800 rpm if there is no converter slip. That really is not all that bad if you are not going to be driving it a bunch. My Chevelle had 3.73's in it and I put almost 50K miles of daily driving on it like that when it was new including many a 70mph trip from Maryland to Mass. Thats 500 miles each way. It was a small block and they like the rpms, but a well built Rat can handle it too.

Just my opinion,

The 3.73's will be fine...especially with a "short" stroke 396. If it gets a little too much, you can always tame it down some with a taller tire.
I run 3.73's in my '70...works fine with a 28" street tire AND a 30" slick. :thumbsup:

I would agree with 3.42 over 3.73 with that 60203 VooDoo cam.

If Im not mistaken that cam calls for about 2500 converter and 3.23 or larger rear gears no? Id so 3.42 puts you right in there.

I have run many cars with a 275/60/15 tire with the 3.73's, you will be very glad you did.

I'm gonna stuff a moderate 454 into my 70 Elky. In prep for that, I had 3.42s installed and a fresh Posi. With 255/60-15 and a Mild Mouse, I now pull 2600-2700 rpm at very moderate freeway speeds with a TH350 and stock converter. A lot of the NW guys are running 3.31s--3.42 but most up here are running FatBoy 454s and large bumpsticks.

I will tell ya that Matt is unhappy with his 3.73s that came in his 70 454 Elky, wants 3.08--3.31, better cruising. Ben loves the 3.31s in his 454HO 68 SS Elky.

mc71454 with 275/60/15 and 3.73s sounds good too.

Simply a matter if you can tolerate the extra noise on the freeway and a bit less mpg.

if you want the best performance and still have some drivability then you need to go with your thinking and stick those 3.73's in there. from my experience mildy warmed over 396's and 402's LOVE 3.73 gears.

from my experience mildy warmed over 396's and 402's LOVE 3.73 gears.

yup.I agree

3.73's here. 28" tall tire normally but I have extra rims I use for weekly driving with BFG DR's 295/65R15's and they mellow out the drive alot. 3.73's are a good all around gear for street and strip.

Will there be that noticable of a difference with the seat of the pants torque feel between the 342s and 373s? Or will the torque make it not really noticable. I want some pop when she spins and spin she shall!

Tim

doubt if you'd notice any diff between the two in normal driving except it'll be a little quieter and smoother on the freeway with 3.43. the tire roasting won't be much of any different, a little more tire RPM at the same engine RPM for improved frying technique. :)

i'd say you'd definately feel the difference. your combo from the carb to the convertor is a perfect match for 3.73 gears, imo.

My original Z-28 went 70 MPH in 1st gear with 2.2 4 speed, 3.73 rear, and 26" tires. Even with 26" tires, it was not a bad hy-way car. However, for a REAL street driven car, I think 3.73 is as low as you should go. 3.31 is a great gear for anything about 400 CI. Since the after market doesn't make 3.31's for some reason, I would go with the recommended 3.42's.

For what it's worth, my 73 Monte towing package came with 3.42's, and I thought they were too low.

Tim - I have 373s with my 454 stick car. If I did more highway driving I'd want an overdrive or some lower gears. With the tires you mentioned you will not have a problem breaking them loose with either set. As others said - that engine will still be fun with the 342s.

what gears was your converter set up for?

If you do no more than 70 on the highway for extended periods, then the 3.73's with 275/60/15's would be a good compromise. That is what I have in my truck, and it just begins hitting the sweet spot on the cam.