dukvet76

Okay, so I've modded the engine, 350block, bored .40 over, ZZ4 heads, XE268H cam, carb rebuild (q-jet), TCI breakaway 2400 stall, K&N, roller tip rockers, bla bla, and still no torque.

So there are 2 things left that I can do.

1. I need to get the tach recurved to match my engine (or can I buy a new one?)
2. Should I switch out my gears from the 3:08's to 3:55? My buddy has 3.70's in his, but he can't go over 80kms/hr in it on the street.

Thanks!

Wrencher

You didn't mention transmission, but with a stock 4 speed or automatic, the 3.55's are a good compromise for a street car and will most certainly help your low end. If you had gobs of power (including more torque), a modern 5 speed with a lower 1st gear would also solve the problem.

Hans

Fast81

which tranny ??????

3.55 ====> OH YEAH

BeaterShark

Going to 3.55 gears from 3.08's will increase your torque by 15%. It will also change the 70mph cruising from 2700 RPM to 3100 RPM, assuming 27" tires.

Fevre

No need to change the tach, one revolution of the eng equals one revolution no matter what you do to the eng or trans but you will have to change the speedo gear in the trans. One thing you can check is your timing curve, make sure you are getting about 36 degrees adv at 2500 to 3000 rpm's with the vac can unhooked.

Alwyn678

absolutely and 3:73's are even better :smash: :cheers:

Paul L

You may have made an error in question 2 as 80kph is 50mph. Even with the 3.70:1 rear end a Corvette will do much better than that.

jrzvette

:iagree:

and 4:11's better still and 4:56's will help you pull down trees, but your milage may vary.

dukvet76

FYI, I'm running the stock 350 Transmission.

PAUL: The setup of my friends vette is: 327 small block, 350 transmission, holley carb, chrysler distributor, b&m shifter, huge stall, like 3200, and 3.70 gears. He won't go distances in it over 80kms because of the RPM it runs at. Maybe it's the combo stall/gears that's causing this.

dukvet76

FEVRE: My distributor needs to be rebuilt or recurved. I was wondering if I could just get it rebuilt or buy a new one that would perform better with my engine setup. I do understand that it has nothing to do with the gears. It's really a separate issue. Thanks!

MotorHead

You must have a auto I have 4sp with 2.88 first gear combined with 3.08 rear end gives me a good launch, so good I would not change it

If you have no torque I would try and dial in the engine first usually takes me a while to get a new combination running properly. :D

Fevre

Contact Lars (that is his name and forum name), he is the forum carb/dist guru.

BTW I think you meant dist not tack in #1 of your first post, why I wrote that about the tach.


[Modified by Fevre, 11:38 AM 10/14/2003]

MikeC

Yeah with 3.70's 80k is around 2500RPM.... THe converter isn't even stalling yet so he's probably doing around stall speed. Not a bad gear a little much for the 401 though.

WHy is his stall so frickin high on a street driven vehicle? If he were to put say a 2200-2500rpm converter in it it would be a much more friendly car... and it would only hurt his launch, a few tenths in the 1/4, for a more friendly car.... I'd definitely do it.

norvalwilhelm

I removed a set of 4.11's from a customers car but test drove it first with the 4.11's and it was snappy. I then pulled the gears and install a set of 3.08 and immediatly test drove the car. It felt like a dog, felt like half the motor was missing.
While you won't feel this much difference there is still a difference, you are just down the curve more.

Glensgages

I agree with others here; your buddy's problem (80km/hr max speed) is due to the converter, NOT gearing.
3.55s shouldn't be a big deal for you; even Z28s of the late-'70s CAME with 3.73s from the factory.
Assuming you run 27" tall tires (various-make 255/60R15s), with a THM350 and a 'stock' converter (no lock-up), you'll turn approx 330 RPM per 10 kh/hr with 3.55 gears.
I envy you, making the Wasaga Beach Cruize............
:banghead: :cry :mad

Fevre

Plus he is going to burn up his trans driving around below his stall, the stall rating is where the convertor acts as a locked unit, below that the convertor slips generating heat which kills auto trans. You want to do most of your driving above your stall rate unless you have a locking t/c.

73jst4fun

Made that change over last winter from 3.08 to 3.55 and it felt like a new car with more zip. I had to change the speedometer gear in the trans to a larger tooth combination so it read correctly. 3.73 would have been a bit much for any turnpike/interstate driving that I do but driving locally it's perfect.... :thumbs:

LT1driver

you will love them, I had them and liked them alot and they were with a big block, have 3.70s now with s/b, great in town, but too busy on road for me. Go for it. :D

Glensgages

The OD-feature of the 700R4 is it's SOLE redeeming quality; with 3.73s & the .70:1 OD, it still 'feels' like it has 2.61 (3.73 x .7) at highway/Interstate speeds.

dman535

The 3.06 first gear is also a significant redeeming quality !