Ok, so i have a 65 f-85, 330 rebuilt to stock before i bought it. I plan on adding intake, cam and lifters, roller timing chain. Right now I have opgi w-30 manifolds thats going in soon with 2.5 exhaust, going to install a rebuilt turbo 350 soon. Now, the rear end gears are 3.08, not posi. What do you think about adding 3.36 with a posi?

 

I don't think the 3.36 is an option with Olds rear ends. But you could go 3.23 or a 3.55. The 3.23 is a good all around gear, but if you wanted it a little snappier the 3.55 might be worth considering.

 

3.36 3.55 3.73 3.90 4.33 4.10 4.56 4.88 5.13 are all available in the after market of GM gear ratios are underlined. .
The deal with your differential is that a 3.08 carrier can only hold 2.93 3.08 3.23 ratios
The 3.36 -5.13 will be on the next series carrier up
SO do think about that.
Why would you not want to keep the 3.08 gears? They are great for all around driving and still can have some fun at the track.
You just need a posi and I would re bearing the rear. GOOD to go!
We have all the other 3.36 posi bearing etc... if you still want to go that route too.
Jim
JD Race

 

Yes. i'm going to keep the 3.08 and just add posi, thx for your write up! Where can I get a posi
for the 3.08,? Or how about the lock up? Rather go posi

 

Great engine, I assume the low compression 250 HP version ?

If so I had the same spec engine in my first car a 1967 Cutlass Holiday Coupe. It sold me on Olds for life, going on 35 years now.

Mine was 3 speed manual and 3.08 rear. Definitely made for quick acceleration back in the late 1980s. But if I were you and you are going into the rear anyway for limited slip purposes I would go with a more aggressive gear as well. Talking to car guys over the years that daily drove these type of cars back then you don't want to exceed 3.73 or it will likely drive you nuts on a non overdrive transmission.

You can ease off the gas pedal on an aggressive gear, but cant put the pedal trough the floor when asking for more ...

 

No, 10.25 compression with 4 barrel. Have not really driven it yet, I would not want 3.73. I would say 70% street other hwy. I'm going to keep the 3.08 and just add posi.

 

Also think about what you think is cool. Acceleration or just plan burn outs. ...3.08 will not affect a burn out...the more freeway type gearing the more SMOKE in the burn out.
Gears are for making the car go from point A - B quicker...BUT remember too, traction is ALWAYS an issue on the street and your only going to get so much acceleration on the street from a DEAD stop.
We did a Monza with a small block and it is only a Summit Budget TABLE motor long block that was dropped upon delivery (valve cover muffed. ) Swap the vavle cover did the edelbrock performer intake 600 holley
350TH trans 200 stall left the 2.56 gears in the 7.5 and installed a posi ...We run that car everywhere and it is the most driven car in our house hold as it is just fun torquey driver with no worries ...does 1000 foot burn out and still drive 80 on the freeway...
Youngest daughter plays at the track with it in the JR Street... 14.50 1/4 mile and 9.50 1/8th ...this class can not go faster than the 9 sec mark in the 1/8th mile. Kids with out drivers license yet and a parent need to sit in passenger seat down the track..
She does JR Dragster too 7.90 1/8th 140# weight added to slow it down... these things really go... 85 mph
LOOK AT THE REAR SLICKS ON THE JR.! LOL 1.57 60 FOOT

 

 

double check those w30 exhaust manifolds, big block manifolds may not work for you

 

I got the opgi manifolds that bolt right up

 

i think you will find the 3.08/th350 combination quite responsive.

 

I'm sure it will be!

 

Which "OPGI manifolds"? Real BBO W/Z manifolds will bolt to any Olds heads. They will not clear the starter, motor mounts, or other parts on an SBO when installed in the car. The aftermarket SBO manifolds that are claimed to be "W30-like" manifolds are the same size as any other SBO manifolds. The emphasis is on "claimed to be."

 

Thornton manifolds, drivers port is bigger than stock and no more cross pipe

 

The new W-31 manifolds will work not the 442-W-30.

 

Actually the OP has a 1965 330. His "W30" manifolds are actually the Thornton aftermarket SBO manifolds that are supposed to look like W/Z manifolds. Emphasis on "supposed to".