DEMITRISTYLES

I was thinking about 3.73, but maybe that's too much. 3.55 might be a better option?!?!

I'd like to drag the car occasionally and don't want to sit there spinning.

Here are the motor specs...

406 - 547HP @ 6500, 510 ft/lbs @ 4750
Edelbrock Victor Jr. heads
Comp Cams XR280R Solid Roller 242/248 deg @ 0.050 - .608 in / .614 ex
Hi Tech rockers 1.6, Scat crank Eagle rods, SpeedPro 11 :1CR, Vic Jr. intake

mrvette

500 hp?? I change my vote from 355 to the milder gearset 307, no need to turn ~15% more rpm's at speeds, plenty of TQ to move the car unless you using sticky mickeys.....

Gordonm

I'd stick with the 3.55 gear. I have 3.70s in mine and it is fine but might go to 3.55 if I had to change. With a 3.0x gear your OD might be to much and the car would be real doggy in the 60 mph range depending on your cam.

Eddie 70

I have 3.36 in mine and like the performance around town. This was the stock gear for my car at the time. This gear worked great with my old motor and the mild cam I had in it. I don't know exactly how it is going to perform with the cammed LS motor. We will see.

MotorHead

If the gear ratio's are 2.74 first, 1.57 second, 1.00 third, .67 fourth. Then I would go with 3.36 or 3.55 at the most, that motor has near 400ft/lbs @ 2000RPM, no worries about lack of torque there. You need to select the proper torque converter too

If it were mine I would just put a converter with the correct stall in it and see how it is with the 3.08's :S

Theiskell

I have the 200R4 with 355 rear gears and about 400-425 hp and love the gearing. I think you will be happy with the 355. It has good low end power and cruises at 75 turning about 2400, whats not to like

Glensgages

my recently deCross-Fire'd '82 has 3.73s behind it's rebuilt 7004R (.70:1 OD ratio), and with 4th Gear/lockup, there is about a 3:1 ratio between the speedo & tach
(60 MPH = 20 hundred RPM)

As MotorHead suggests, having a long-stroke 400" SBC probably provides you with a very broad torque-band, capable of 'pulling' a taller rear-gear like a 3.36 or even a 3.08:1 ratio, especially with a First Gear ratio of 2.74:1:
I believe ISOSCELES ran 12.90s with an old 383" SBC motor of GSC3s, a 200-4R and 3.36s on UNIROYALS a few years ago

larrywalk

Considering the size of your engine and it's power, if you choose too low of a rear gear with the first gear multiplication of the 200R-4, you WILL have a problem with too much torque at the tires (tire spin); and then, if you use slicks and hook up, you WILL have a problem with driveline breakage if you multiply the torque too much with low gears.

A good gouge for this is to make sure that the first gear ratio times the rear end ratio is not greater than 10; if you have a torque converter stalling greater than ~2500 rpm, go to a higher number such as 9 or 8.

As an example, my '78 has a 406 with 3.08 gears and a TH-350 - the numbers are 3.08 times 2.52 for a 7.76 total ratio. With my tight 10 inch Continental converter (2,800 brake stall), I run 1.79 60 ft times and a best of 11.96. This is with MT Street ET (drag) radials, without which, it won't hook up. Since your engine sounds stronger than mine, I'd recommend 3.0 to 3.3 as a rear end ratio unless you're running drag radials or slicks.

Alternately, if you run a PowerGlide (1.76 first gear ratio) and a 5,000 stall converter, I'd recommend 4.11s.

DEMITRISTYLES

Does a 3.55 gear and a 3000 stall sound like a reasonable combo for my cam/engine?

DEMITRISTYLES

vote vote vote!

Glensgages

..... after reading this, the polling-booths should be closed

if you make more power, would choose 3.08s, and have 10% more TQ-multiplication in 1st Gear, it makes-sense that you could run similar short-times & 1/4-mile ET as Larry

gkull

A TH200-4R overdrive automatic utilizes a First gear of 2.74, a Second of 1.57, a Third of 1.00, and a 0.67 Overdrive. With this transmission's First gear ratio of 2.74 combined with a 3.73 axle ratio, the final drive ratio >> yields a 10.22 (2.74 x 3.73 = 10.22). In overdrive, the final drive ratio equates to a Bonneville-ready 2.49:1.

I have a 4.11 and OD. 4.10X.70 = 2.87 over all. which is pretty good for the freeway. I always figured that 3.90 would have been the best.

The problem with big duration SR cams is that they don't have much go below 2000 rpm. So if you over gear like 3.55 if forces you to drive pretty fast before you can even put it in OD

mrvette

Which gets right back to the cam, idle and tq range of the engine....

I not a fan of loose converters, when tranny shifts, I don't feel a kick in the *** like a stick shift...so I like a truck/tight/snug converter so I get that pleasant bump in the *** when it shifts....
YMMV depending on the small one next to you, that with the higher pitched voice, and control over the kitchen.....

Little Mouse

3.55 would give you same as 1 to 1 2.30 high gear 9.72 low gear
surely 2.30 bonneville salt flats gearing is enough. 9.72 is a pretty nice
low gear you would not need a real sloppy converter. I like your 3.55 plan but if you have 3.07 now nothing saying you could not try it first see how you like it.

gkull

Have you driven one of the new highly efficient TC's? the reason I ask is because I had a 3800 stall lockup converter and a tranny that shifted so hard even just cruising down the road that felt sorry for the U-joints on every shift. the TC didn't slip it banged every gear

v2racing

My 80 with a 406 has a 3.07 gear behind a 700-R4 with a lock-up converter that stalls at about 2800. Most of the time it is more than street tires can handle. You do have to cruise pretty fast to use overdrive.

MotorHead

You use overdrive on the highway, 75mph ++, up here the minimum the cars are going on the highway is 75-80mph anyway so the 3.08 and his overdrive puts him around 2000RPM and no problem with that motor

Nemesis_152

agreed on the fact that it wont be a problem in terms of power available at 2000rpm, but i'd think that such a big cam would be more efficient if he got it up a bit higher (~2400rpm or so). could make a slightly more efficient cruiser, even at the higher RPM range.


writer's note- i'm just hypothesizing, i have no experience with the particular setup in question.

gkull

My one last piece of advice is that you just have to live with what ever first gear is and only worry about 1-1 and OD

Dumb asses that tell you about 2000 rpm going down the road don't own a hot rod. Much less a solid roller 406. you have to do the math. Motors that can rpm can do high speed. I have a 4.11 and don't even shift into OD until I'm doing 135 or 140 mph. Dumb asses think they have body lift and the car floating when they got the their POS doing 110 mph because they don't do prior proper planning.

If you over gear you don't have much acceleration in top gear. Even with my good aerodynamics. My 79 vette is slow to gain speed over 160 mph. It is the same with NASCAR cup cars on the super speed ways. It takes two laps in the plate motors for them to be in the 190-200 mph range.

In a higher rpm car if you go drag racing. look at your tire diameter and rear gear calc's. with my 700R4 and 4.11 with 10X28 slicks I was doing near 90 in second and not even near my red line in 1-1 third through the lights doing 11.70's @ 118 -120 mph

OH ya, dumb asses that want 308 or 3.36 with over drive............ That comes out to 278 mph in top gear at 7000 rpm. Aren't you a little smarter to gear for sub 200 mph

mrvette

I don't think so, dunno your point of reference really, what is so different about them?? they have to slip at lo rpm's for any given engine idle/rpm so I know those 'stall' ratings are really just a SWAG point....

what are you referring to??? and who makes them, and what is different about them internally/externally???