With an M-20, would the cost to go to 3:42 from 3:07 be worth it both financially and seat of the pants ?
Thanks.

yes and yes....my 67 runs a 3.42 now. it came with a 3.55. imho 3.42 is as low as you want to go on the street driven chevelle with normal o.d. tires. just swapped out to a 700r4 so it is just icing on the cake....496/600hp motor....

Novice to this. How do I tell what to buy and from where ?
Thanks.

i guess to me it depends on who is going to put in the parts. BGH and i both sell parts as do many speed shops. if your local shop is doing the work, they appreciate you buying parts thru them.

BGH and I give support to people who buy from us. try that with the big catalog stores. I can also beat the catalog stores in price most of the time. Most of my parts are in stock also. Even the internal replacement parts like, spider gears, shims, yokes and the like. tom

Definately worth it,i went from opt 307 gear in my 12 bolt to 3.31s with m20 and mild 396,really woke up the the old seat of the pants /BUTTOMETER perfoamnce in my case.

But 342 would do an even better job with seat of the pants feel but if your not running enough motor/cam the car could end up slower in the long run in 1/4 mile strip racing even though it truely feels & seems faster so be aware of that.

In my car with mild 396 now 402 with the 331's, m20,& with 225/70R14 BFG's its turns approx 2,650 rpms @ 60mph & 3k rpms @ 70mph .

So add approx 100-150 rpms or so to my cruise rpms for 342's and thats what you will get if running same approx tire size/hight.

As for cost,gearset approx $150-$200 then another $450-$500 for labor and parts like rear end cover gaskets,pinion seal,oil,axle seals,ring & pinion setup shimes/etc.

Could easily end up $700-$800 when all is said and done for parts & labor even if they dont find any other issues/worn parts that need to be replaced thay you/they didnt count on getting into at that time. Like for example carrier bearings,axle bearings,posi clutches,rear end yoke,u joints,etc.

BTW,the dirshaft is going to be spiing considerably fasted and i have foind over the yrs with thses old cars that in cases like your going for more gear its a very good idea to at the same timing to replace both u joints and have the driveshaft reballanced too.

If the trans yoke is worn at all i would also replace that at the same time too .

I found that generally when installing more gear spinning d-shaft faster tha unless in did the above mentioned items i would end up with driveline vibrations every time,sometimes minimal sometimes bad.

There goes another $100-150 if you end up with dirvetrain vibes ,i did going from 307 to 331 so i can and does happen. I had them installe 2 new u-joints,new trans yoke,then ballanced shaft and that fixed the vibes with more grear.

But that was only uintill the nut on the rear end yoke came loose because they didnt use any loctite on it which is another story for another day .

Thanks...Scott

Yes. I could tell the difference in my brothers 70 SS when I changed from 3:31 gears to 3:08 because he wanted more highway friendly gears. He wants to go back now after running a 14 flat quarter mile time.

With an M-20, would the cost to go to 3:42 from 3:07 be worth it both financially and seat of the pants ?
Thanks.

Dave,
Freddie Byers (BIG GEAR HEAD), right here on Team Chevelle is the guy to get in touch with.