Hey y’all, in the process of rebuilding my 85 cutlass. Have a 383 with bow-tie aluminum heads/ lunati cam, need to get a transmission for it and need some help deciding what to get. Not sure if I should get a built th350 or something different. Have stock rear end but that is going to change shortly after car is up and running. This is not a daily... going to be a weekend car and something I could bring to the track. Any help would be appreciated
Recommendation for cutlass
- Thread starter Texas_85
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Built 200-4R so that you can put in the 3.73's or 4.10's and still cruise. Best of both worlds.
I was only worried about possibly robbing to much horsepower considering I’ll probably be in the 400-450 range
Power loss is overstated between a 350 and 400. General concensus is there about an extra 15 to 20hp lost with the 400 from most of what I've ever heard.
You can make that up by going with a lightweight aluminum wheel to remove rotating mass and never worry about blowing the trans if it's built right.
You'd notice that loss more with a 200hp motor than with a 400hp one. But either way, a good builder is more important than your choice. Done right either will last and do what you want as long as the guy is competent and you're willing to pay for the correct parts.
Better to build for your application custom than just buy a generic off the shelf unit as well.
Awesome thank you for the amazing advice. Would you happen to know a good gear ratio to run in the rear end as well?
In my opinion there's no one size fits all recommendation, here's why.
First, every engine build has a different powerband and torque curve. If you're putting together a serious 400-500hp motor it's worth getting dyno'd.
You'll see best acceleration if you pick your combination of transmission, gear ratio, and tire size to optimize staying around your peak power curve.
Choosing wrong is why guys buy crate motors advertising lots of horsepower, pick tires based on "look" then toss in a popular gear set and don't understand why they're so slow.
There's TONS of online calculators out there that will let you plug in various combinations. You can enter a random gear set, a tire size, and a transmission and it'll tell you how many rpm you run at a given mph. Then you can match that rpm to your dyno curve. It could be that a certain trans/gear/tire leaves you mired in the 200hp range of your 450hp motor so it feels like a dog or that it runs out of top end.
Here's one: https://www.sierragear.com/differential-repair-help-topics/differential-gear-ratio-calculator/
I had a better one saved on my old laptop, but, I'm on the smartphone right now so it at least gives you an idea.
Hard to beat a 400 for durability - been racing the Regal for 20 years and never had a problem w/ the 400. 350s are a good trans after putting some good parts in them. I'm running a stock L-82 350 short block w/ a comps 306s cam 2.02 iron heads, vic jr with 750 and still putting about 450HP to the rear wheels
I had a Malibu with a 425hp sbc and th350 trans. I ran both 3.42 and 3.73 gears. My opinion for a non-OD trans that sees regular highway/cruising duty the 3.42 was as numerically high as I would go. If it’s track only, 3.73 or higher.
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