Big Cubes, OD + $$$$$

[G-Body_Vet]

The time has come to make a cam choice and I need to make a decision on the the rear end gear + trans. I originally planned on using 3.23's and a built 200-4R, but after looking at what I'm going to spend to withstand the torque I'm having 2nd thoughts. Speaking of torque, I can probably live with a high rear gear (2.56's).

So....my question is this:
Who else is using a big block, th350/th400 with a high gear? My end goal is a street cruiser with reasonable mpg. Yeah I know, gas mileage and 455 don't belong in the same sentence but you get the idea. I'd like to make a couple of short road trips in this car too when it's done. The bottom line is the cost vs. benefit of a few mpg.

Thoughts, opinions, etc?

 

[rccktmn2]

There is a calculator at richmond gear that pretty much tells you what you need to know. http://www.richmondgear.com/101032.html

The big question is are you taking it to the track? In my opinion a good gear to have for a big block with od would be a 3.73. you can utilize the low end torque, still have good rpm's for take off and acceleration and with the od keep your gas mileage. Your overall rpm should be between 1500 and 2000 for optimum fuel mileage. Just my opinion, hope it helps.

 

[454cutlass]

i have a 454 with a th350 and 3.42 gear. drove around town fine not to friendly on highway but doable ( high rpms). never got numbers for mpg didnt seem to bad

 

[G-Body_Vet]

There is a calculator at richmond gear that pretty much tells you what you need to know. http://www.richmondgear.com/101032.html

The big question is are you taking it to the track? In my opinion a good gear to have for a big block with od would be a 3.73. you can utilize the low end torque, still have good rpm's for take off and acceleration and with the od keep your gas mileage. Your overall rpm should be between 1500 and 2000 for optimum fuel mileage. Just my opinion, hope it helps.

I've played with those calculators a million times. The car will never see a track and honestly I think anything bigger than a 3.08 will result in non-existent traction with 500+lb ft of torque. I frequent the Pontiac forums too and lots of guys are claiming halfway decent mileage with a good tune, q-jet, TH400 and 2 series gearing.

 

[khan0165]

can't speak from my own experience... but,
a friend is running a olds 455, aluminum heads, big cam, the works... Backed by a M22 Rockcrusher Muncie.

... with this wide ratio M22 (not sure on ratio numbers), he is using a 3.08 rear gear. I believe he turns 2200rpm on the highway @ 60mph.

... still buzzing for a 455, but liveable.
... and much better than his previous th350 & 3.73 gears.

With the Olds torque, he still pulls hard thru every gear, can launch in 2nd if he wanted, and still spin in 4th. So don't be afraid to run a high gear on your motor.

 

[JBreu]

I'd say go with 3.55 gears........and a 700R4 transmission 🙂

 

[G-Body_Vet]

I believe he turns 2200rpm on the highway @ 60mph.

I do a lot of expressway driving at 75mph....to keep up with traffic of course 😀 . Launching and accelerating won't be the problem, it's cruising at higher speeds without having a buzzbomb underneath me. I've done the TH350 & 3.73's before and I can honestly say never again!

Ideally, 3.42's up to 3.73's with OD would put me in a good rpm range, hence why I wanted to use OD. Realistically I can be a cheap b*st*rd at times and I don't want to shell out the funds for a built OD trans.

 

[papabearxl]

I say the 200-4R, and the 2-series.....I won't have the 455 (will have the 333) but I do have the 200-4R and am going to keep the 2:56 rear gear, just to see what mileage will be......if good enough (maybe 20mpg), I will drive it to work most days, 80 miles interstate driving total.....I may be wishing too hard, but I am hoping.

 

[papabearxl]

You, of course, will have LOTS more torque than me, so I think you will do good with the 2-series and OD....and still have tons of power.

 

[dogsht]

At minimum we need compression ratio in addition to what you have provided to make a decent cam pick. If you have decent 9.0+ to one compression & hopefully some head / valve job work probably something near 230@50 duration. For box cams I like Lunati.

http://WWW.extremeautomatics.com has the 200-4r that you need with warranty for 1,495. Cheapest route possible.. no, but worth it. 3.42 with the overdrive makes for a final drive ratio of 2.29! You save another 2 to 3 hundred rpms from a lock up converter that both helps it stay cool and is good for an additional 1 mpg. The lock up converter is also great when you want something that both shoots out of the hole quick AND drives & cruises nice. It's also lighter and more efficient as in soaks up less HP to operate when compared to the th350/400 or even the 700-r4. 33% better fuel mileage is only a side benefit of an overdrive transmission for a high performance true street car. It with a proper gear to match your power plant is the single best upgrade you can make to fast say power tour capable street car.

BTW I built the 509ci 442 in my pics that got 17.0 mpg on a multistate interstate trip. My secret..200-4r, working lock up converter, Q-jet, and a reasonable cam. It had 28.0" tires in the rear and 3.42 gears at that time. It did that two days after its get acquainted pass at the strip where it ran 12.5 at 110mph.

http://WWW.robertpowersmotorsports.com. Bob ran a best of 12.3 at 110 & got 15.5 mpg hwy still tuning with his Olds 455 powered Cutlass that had a 200-4r, lock up converter, q-jet before it was stolen.

Dwight has a car domain site that shows his 455 olds Cutlass where he runs 12.0s & got like 20 hwy. Again overdrive. Lock up converter, q-jet, reasonable cam. His car has been was featured in Car Craft.