1988 Cutlass Supreme Classic SBC Build

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88cutclassic

Not-quite-so-new-guy
Sep 24, 2022
10
4
3
27
Victoria, BC, Canada
I'm looking to buy a new ring gear and stall for my cutlass. I've got a 7.5 posi to go in and I'm leaning towards either 3.42s or 3.73s but probably 73s because of a more aggressive launch. No idea on what size for the converter though. The car will see both the highway and city driving frequently.
Build is;
-355 SBC (.030over) aluminum heads and a 268xe cam
-200-4r
-26" rears
I want to be able to smoke some folks in town but also not get 16mpg on my road trip planned from Vancouver Island to New Orleans.
An online calucator says 3.73s would give 60mph @ 1950rpm and 77mph @ 2500rpm which are highway speeds in my area. Toqrue lock-up will be done through the 200-4r painless wiring kit. What are your guys thoughts?
 
Everything is a tradeoff. You can build for speed and smokeshow launches, or you can build for gas mileage, but going one way costs you points from the other. I'm assuming this is not your primary vehicle, so you should build it for fun and not worry so much about gas mileage. Tune it right and match components well and you'll maximize the power per gallon ratio and gas mileage will be whatever it is. And all-around fun is more important that HP or mileage alone. Always remember, it ain't no smog engine you're dealing with. Expect the worst and hope for the best on fuel mileage. That should be concern #42 on the top 10 list of things to worry about building your car.

With the 200-4R, I'd go with the 3.73. The stock Monte SS, H/O and 442s came with them and a tiny bit looser stall converter for a reason. 3.42 will wake it up assuming it's a stock rear you have in it now, but I think you'll benefit more for what you're wanting to do in town with 3.73 with the OD. If you had a TH350, I'd probably go with the 3.42-ish gear range.

The stall? Usually a personal choice, but my personal choice would be somewhere in the 2500-3000 range of stall. Don't know your dyno sheet, but figuring a mild build <400 hp, you're not a full tilt race engine. Since it'll lockup on the highway, the stall speed can have a little more relaxed approach. I see no reason to go above 3000 for the street in your application, IMO, but again, I'm not building your sled.

Your opinion may vary.
 
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I agree, something around 2500 for the converter will help. If you have enough overdrive, go with the 3.73's. I think overdrive is a great idea, but I don't agree that we should drive the engine rpm so far down. The cam is oiled by crank splash so having it lug down the highway at 1500 may sound good for gas mileage, but I feel its better being up around 2000-2200 at whatever your target speed is.
 
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I agree, something around 2500 for the converter will help. If you have enough overdrive, go with the 3.73's. I think overdrive is a great idea, but I don't agree that we should drive the engine rpm so far down. The cam is oiled by crank splash so having it lug down the highway at 1500 may sound good for gas mileage, but I feel its better being up around 2000-2200 at whatever your target speed is.
3.73 and lockup should put him a tick over 2K at 60. He should do fine.
 
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Everything is a tradeoff. You can build for speed and smokeshow launches, or you can build for gas mileage, but going one way costs you points from the other. I'm assuming this is not your primary vehicle, so you should build it for fun and not worry so much about gas mileage. Tune it right and match components well and you'll maximize the power per gallon ratio and gas mileage will be whatever it is. And all-around fun is more important that HP or mileage alone. Always remember, it ain't no smog engine you're dealing with. Expect the worst and hope for the best on fuel mileage. That should be concern #42 on the top 10 list of things to worry about building your car.

With the 200-4R, I'd go with the 3.73. The stock Monte SS, H/O and 442s came with them and a tiny bit looser stall converter for a reason. 3.42 will wake it up assuming it's a stock rear you have in it now, but I think you'll benefit more for what you're wanting to do in town with 3.73 with the OD. If you had a TH350, I'd probably go with the 3.42-ish gear range.

The stall? Usually a personal choice, but my personal choice would be somewhere in the 2500-3000 range of stall. Don't know your dyno sheet, but figuring a mild build <400 hp, you're not a full tilt race engine. Since it'll lockup on the highway, the stall speed can have a little more relaxed approach. I see no reason to go above 3000 for the street in your application, IMO, but again, I'm not building your sled.

Your opinion may vary.

Thanks for the reply. Yeah I think I'll go with 3.73s.
Everything is a tradeoff. You can build for speed and smokeshow launches, or you can build for gas mileage, but going one way costs you points from the other. I'm assuming this is not your primary vehicle, so you should build it for fun and not worry so much about gas mileage. Tune it right and match components well and you'll maximize the power per gallon ratio and gas mileage will be whatever it is. And all-around fun is more important that HP or mileage alone. Always remember, it ain't no smog engine you're dealing with. Expect the worst and hope for the best on fuel mileage. That should be concern #42 on the top 10 list of things to worry about building your car.

With the 200-4R, I'd go with the 3.73. The stock Monte SS, H/O and 442s came with them and a tiny bit looser stall converter for a reason. 3.42 will wake it up assuming it's a stock rear you have in it now, but I think you'll benefit more for what you're wanting to do in town with 3.73 with the OD. If you had a TH350, I'd probably go with the 3.42-ish gear range.

The stall? Usually a personal choice, but my personal choice would be somewhere in the 2500-3000 range of stall. Don't know your dyno sheet, but figuring a mild build <400 hp, you're not a full tilt race engine. Since it'll lockup on the highway, the stall speed can have a little more relaxed approach. I see no reason to go above 3000 for the street in your application, IMO, but again, I'm not building your sled.

Your opinion may vary.
Thanks for the reply. I agree that all around fun is the most important aspect. I think I'll do 3.73s paired to a 2500 stall. Gas mileage is normally insignificant to me, however if I plan to cover 5000+ miles; 2-4mpg difference adds up quick. With that being said I will probably experiment with different rear tire sizes if I find the highway mileage to be atrocious. Thanks again 👍
 
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