Have a 505 CI BB going into a 71 RR, I'm thinking 3800# or so.

Engine Dynoed at 620 HP and 650 torque flattening out around 5500 RPM
950 Holley, dual plane Indy max wedge on Eddy Victors.

Going to a Dana w/3.54s.

Car will go to the track maybe twice to sort out tires and suspension,
but will be primarily street driven weekends to shows and meets.

I'm thinking a tight 11" 2600-3000 with furnace brazing and an anti ballooning plate.

Does this sound like a combo that will work?

Thanks in advance...Joe

You could probably go even tighter (2300-2500) and it would drive better on the street and be a LITTLE less prone to blowing off the tires off the line. Regardless, you're going to need a custom built converter to live behind that much torque. Nothing off the shelf in those stall ranges is going to hold up for long.

Converters are a lot like camshafts...I'd have it built based on what you're actually going to do with the car. A tight converter will be more responsive and feel faster in a street car. Especially with a motor making that much torque.

I agree with all thats been said. If you aren't shooting for a great ET at the track, what is left is street manners, feel, and STREET TRACTION. By that i mean why put up with any less responsive converter when a real tight one will still fry the hides? Personally i would shoot for about 2600 to 2800 stall behind your motor. A converter that tight will move out smartly at the tip of the throttle like a stock 440 converter combo (only harder!) and be a blast to drive on the street. A good converter builder should know how tight you can go with the cam specs and other motor specs so it won't fall on its face from a dead stop.

Thanks for the input gents, all good ideas along the line I was headed.

Now to shop makers, any of the big names to avoid because of service/quality??

Where should the price wind up being close to?

Thanks again, this is the first car in this power range for us.

Joe

Depending on the cam specs(and low speed engine vacuum) a converter that’s too tight will lead to poor in-gear idle and very low speed characteristics, and possibly be keeping the motor operating in an area of the power band where it’s not quite “up on the cam” yet....... during normal “in town” driving situations.

Even my Honda Civic and 2500 Silverado 6.0 have converters loose enough where the engine is rarely below 2200 rpm driving around in town........ and those are 100% stock engines with tiny cams.

Frankly, with MW sized ports, I’d expect the motor to be happier with a little extra rpm(and the accompanying increased port velocity) that you’d get with a slightly loose converter while being driven around town.

Again, for me........ most of the deciding factors would be based on the cam specs and engine vacuum.

Thanks for the input FAST.

We were a little surprised that the engine nosed over so early, but either it ran out of carburetor or the dual plane was not the best pick for the engine.
Forgot to check vacuum at full throttle to see if it was he carb...RATS!

Anyhow, we were pleased at the output, about 40 or 50 above our initial guesses
so after a couple of jetting and timing changes we called it a day.

Torque peaked at 651 @ 4261,
HP 620 @ 5543

Good TQ curve; 621 @ 2821

Does this help?

Joe

PS forgot that these numbers were with the Dyno's 1-3/4" test headers, went to put our 2" headers on and ran into fitment problems with the dyno
so that may account for choking the engine somewhat.

I don’t see any cam specs.

I would have checked the idle vacuum, along with the part throttle vacuum in the 2000-2800 range.

Basically, at least initially.......it’s going to come down to you and a converter shop being on the same page about what you’re looking for...... and then seeing how it pans out after it’s in the car.

Cam specs? Idle speed? Idle vacuum? Tire size & type?

EDIT: Treed!

For a “hot” street motor, making good power is usually the easy part.

It’s making it really Street friendly, and fairly quirk free that’s often the hard part.

a converter that’s too tight will lead to poor in-gear idle

If you don't have power brakes (not enough idle vacuum), you'll find yourself wedging your knee under the steering wheel to hold the car at lights, or it will creep away on you.
You will also be stopping the crank under low speed braking.

Sorry, idle speed was 950,
vacuum, 12 in

By memory, Bullet solid roller , a little over .500 lift
and I asked for a more streetable grind,

Still hunting the envelope with the cam specs... Joe

Thank Polyspheric, I will definitely keep that in mind.

Joe

OK, so much for my memory....

Bullet Racing Cams; Part No. 503000
Dur. @ .50 In. Ex.
257. 264.
Lobe lift 4340. 4340.
Separation 110.
timing events .050 Int 22.5 OP, 54.5 Closed
Ex 66 18
Duration @ .20 In 290 Ex 295
Gross lift 651/651
Lash hot .020
degree intake lobe to 106
10.7 CR, Pump gas (93)

Running a 275-60-15 rear for the street
Have a Hoosier 10-1/2 we use on our 70 Charger to try on the RR just for some idea at the strip

Uhhhh... ignore my 2300-2500 suggestion.

And you're gonna need some sticky tires.

The street BFGs are definitely NOT sticky, we have them on the Charger too, so
some discretion will be needed or a better tire, LOL

Joe

That’s basically going to want something like a really tight 9.5”.

Flash should end up in the low-4000’s.

It’s likely going to need to idle at around 1000-1100 in gear....... maybe even slightly higher.
It will be highly dependent on the timing curve and carb set-up.

In my mind that’s really more of a mild bracket race/hot street strip cam........as opposed to a mild-ish mostly street cam.
Looks like it’s from the UD masters. Same grind I ran in my 448, but on a 108.
Measures closer to 259@.050 with the Mopar sized base circle and .800 lifter wheels.
My 448 was reasonably docile with it...... but I was running 4.56’s and a 5300 converter, with open headers.

I’d expect the idling in gear vacuum to end up under 12”.

I don't like having a tight vert with my 448" .640 cam.mine stalls at 3k and drops to 4k on the shift 9.5 vert 3.73 d60 295- 50-15 M/T ET Street..I am looking at the same changes with vert,gear so I am watching this post to help.

The question is how much do you want to giveup.My car drives nice but it is not as fast.

That is great torque at 2800. A converter as tight as what came behind a 340 , 383 or street hemi(all the same k factor) should stall well over 3,000. I built a 535 with 906 heads many many years ago that pushed a stock converter like that to about 3600! Well, it did for the three runs i made before it ate itself😒. So you have some room here if you want a very responsive package and are willing to give up ultimate ET . A. Tight 11 inch might put the best smile on your face!