Need some advice

64nailhead

Goat Herder
Supporting Member
Dec 1, 2014
4,992
113
Upstate NY
Car will not be a daily driver, something that I can take out every so often for a cruise and be able to take it to the track and have some fun in.
This describes a 3 speed, i.e. TH350 or TH400. If track times are a concern then a TH350 that is well built only due to weight and that you probably won't be exceeding 500hp with your 383.

Converter and gears are dependent on tire size and power band of the motor.
 
  • Agree
Reactions: 1 user

86LK

Royal Smart Person
Jul 23, 2018
1,104
113
I'm not sure what you mean by "in the system"?

The converter needs to match the cam profile & rpm needs of the cam/heads combo to be most effective. If you have a stock converter but a cam w/>240° duration & 210cc heads you'd be leaving a lot on the table performance wise. Same would be true if you had a 3500 stall speed w/a stock cam/heads/<3.0 geared rear end w/>26" tires. The combo needs to compliment each other.
well, if the powertrain system consists of:
engine --> transmission --> rear axle --> tires

...which can then be further broken down into .....

engine displacement and cam profile ---> torque converter --> transmission --> rear axle --> tire size

the only possible variables I see are the: engine power output profile, the torque converter, the rear axle, and tires.

AFAIK, you cannot change the gearing in the transmission itself. this is what I meant by in the system. I've never heard of needing to match the converter to the cam profile which is why I was asking if there was an explanation of how the whole system fits together
 

64nailhead

Goat Herder
Supporting Member
Dec 1, 2014
4,992
113
Upstate NY
The converter needs to match the engine, not the cam or heads or whatever. If you motor’s power band is 4200-6200, then you need a converter that flashes to 4200 and dead stalls 300-600rpm below that.

This is NA, if one was to chuck nitrous in there then it can dead stall lower and work fine.
 
Last edited:
  • Agree
  • Like
Reactions: 1 users

scoti

Royal Smart Person
Supporting Member
Sep 5, 2019
1,654
113
Texas
well, if the powertrain system consists of:
engine --> transmission --> rear axle --> tires

...which can then be further broken down into .....

engine displacement and cam profile ---> torque converter --> transmission --> rear axle --> tire size

the only possible variables I see are the: engine power output profile, the torque converter, the rear axle, and tires.

AFAIK, you cannot change the gearing in the transmission itself. this is what I meant by in the system. I've never heard of needing to match the converter to the cam profile which is why I was asking if there was an explanation of how the whole system fits together
But different transmissions do have different ratios:

700-r4 = 3.06 1st, 1.63 2nd, 1.00 3rd, .70 4th/OD. 1-2 shift ratio drop @ 1.43.
TH350 = 2.52 1st, 1.52 2ns, 1.00 3rd. 1-2 shift ratio drop @ 1.00.
Th400 = 2.48 1st, 1.48 2nd, 1.00 3rd. 1-2 shift ratio drop @ 1.00.
200-4r = 2.74 1st, 1.57 2nd, 1.00 3rd, .67 4th/OD. 1-2 shift ratio drop @ 1.17.


When you search for whatever cam for your given motor, the techs will recommend a converter stall range that compliments the cams lift/duration/rpm profile; hence my comment. Other factors being tire size, gear ratio, & vehicle weight depending how specific ones goal is.

3.73 gears, a 26" tall rear tire, & a 700r4 will make 1st gear useless w/a combo that has a serious bottom end punch.
3.73's, a 26" tall rear tire, a 700r4 & a 8.0:1 compression smog headed, tiny cam motor will enjoy the deeper 1st gearing combo to help it make up for it's lack of bottom end power.
 
Last edited:
  • Like
Reactions: 1 user

scoti

Royal Smart Person
Supporting Member
Sep 5, 2019
1,654
113
Texas
The converter needs to match the engine, not the cam or heads or whatever. If you motor’s power band is 4200-6200, then you need a converter that flashes to 4200 and dead stalls 300-600rpm below that.

This is NA, if one was to chuck in there then it can dead stall lower and work fine.
I apologize if I'm not saying it 100% technically correct but we're talking about the same idea/concept. The cam/heads/compression of a given engine help dictate the power band right? I view the cam/heads as an important part of the engine when it comes to matching supporting pieces.

Please correct me where I'm not.
 
Last edited:
  • Like
Reactions: 2 users

86LK

Royal Smart Person
Jul 23, 2018
1,104
113
I apologize if I'm not saying it 100% technically correct but we're talking about the same idea/concept. The cam/heads/compression of a given engine help dictate the power band right? I view the cam/heads as an important part of the engine when it comes to matching supporting pieces.

Please correct me where I'm not.
I agree with that statement since you can design/build for a specific power band based on block, heads, intake, camshaft profile, exhaust manifold. I figure once you have that built for a specific power range (say 1000-4000rpm), your remaining choices are transmission selection, rear axle ratio, and tire size. Since I already plan using the 200-4r, and the 8.5" rear which appears to be a 3.73:1, then I just need to make sure my tire/combo selection stays within an appropriate size range (not too big) so it has adequate response
 
  • Agree
Reactions: 1 user

ck80

Comic Book Super Hero
Feb 18, 2014
4,547
113
I agree with that statement since you can design/build for a specific power band based on block, heads, intake, camshaft profile, exhaust manifold. I figure once you have that built for a specific power range (say 1000-4000rpm), your remaining choices are transmission selection, rear axle ratio, and tire size. Since I already plan using the 200-4r, and the 8.5" rear which appears to be a 3.73:1, then I just need to make sure my tire/combo selection stays within an appropriate size range (not too big) so it has adequate response
And that's why I love that calculator.

You can select a 700, a 200, a 350 or 400 trans, and it autopopulates the various ratios for each gear. You can SEE how your various specs change as you play with numbers, how different tire sizes impact stuff, it's really cool to play with... or I'm just nerding out a bit.

You cam even side-by-side two slightly different combos and see how they change things.

The only downside is it's somewhat generic and doesn't account for how certain valvebody codes had a slightly better ratio than others for the same trans. But good enough for government work as they say and gets you really really close.
 

RegalRegal

Apprentice
Supporting Member
Nov 30, 2020
95
33
St. Paul, Mn
I would go with a TH400 and a Quickperformance 9" rearend. If you need OD I would go 4l80e, but its more expensive (build/controller). If you still have the 7.5" rear you could always run that knowing it is the weak link and upgrade when time/budget allows.
 
  • Like
Reactions: 1 user

GBodyForum is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to amazon.com. Amazon, the Amazon logo, AmazonSupply, and the AmazonSupply logo are trademarks of Amazon.com, Inc. or its affiliates.

Please support GBodyForum Sponsors

Classic Truck Consoles Dixie Restoration Depot Mike's Montes UMI Performance

Contact Admin@GBodyForum.com for info on becoming a sponsor