Need some opinions on which torque converter

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!

The 1-3/4” header did two things.
It boosted the low end TQ substantially, and killed off a fair amount of top end power....... compared to something like a header with 2” primary tubes and 3.5” collectors.
If you’re going to run 2” headers in the car........ you won’t have that 620tq@2800.

Thanks Greg, I am leaning towards that solution after listening to the various advice.
We have that convertor behind our 70 Charger and are very pleased with it (a stock one).

The 446 in the Dodge has a purple 484 in it which although we are pleased with the performance,
465 HP, six pack, 10.25 CR, it is a very rough and tumble low RPM engine because of all
the overlap on that cam.

I think the 505 will have better low RPM manners and with that amount of torque
and 99% street driving, I think we'll do OK with an 11" that has good innards and a plate.

Thanks all, and I'm still listening...….

Joe

Yes Fast, I realize that, and a 2", 3-1/2" header is what's going on it.

You smart guys sure complicate things and I appreciate it.

It's a balancing act , I know, that's why I'm still listening.

Joe

MP 484 cam....... 68* overlap @ advertised duration
20* overlap @.050

New bullet roller ....... 72.5* overlap@ advertised(.020) duration
40.5* overlap @.050

I have fought this fight. Wanted a tight street converter for my 540 Hemi so that the tranny didn't feel like a slush box on the street. Started with PTC which has been my go-to converter builder for the last few converters and have always been happy with them. Until this last go around wanting a tight converter for a very torquey street engine. They tried twice. Flash was mid to upper 4k. Driving around was not crisp at all, just was way too spongy.

Called Lenny at UCC. First, he told me that the 9" was really too small for what I wanted, but that the 11" stuff was getting difficult to find and very expensive. I told him that I had some motor home converters laying around but he said that there were no parts for them, so...........

I sent the converter to him, he made a few adjustments and made a few suggestions on my end such as a fluid change. And it is much better now. Flash is about 4k and it is much crisper around town. Frankly, I would like it to be a bit snappier down low, but it is not bad like it is. My car likes to idle about 950 and he helped that, too.

And one last thing, check the snout on what ever converter you get. The last two that I have gotten have been a little bit too big to seat in the crank and I had to dress them down a bit. I only figured that out a few years ago after fighting converter bolts that wouldn't stay tight.

Thanks for the heads-up on the snout , Dave.

How did you check it, by feel, bluing or measuring?

Joe

It's sounding more and more like an 11" converter isn't the way to go here, IMO. Perhaps a "tight" 10" that can provide reasonable stall w/o being too slushy? Wonder what Paul at Turbo Action would recommend...

Two 9.5" experiences: In my car, Dynamic (Lupo) nailed it IMO. In Mike Hynes' car (heaver, torque curve much lower, less gear, etc.) his custom-built Dynamic was a big miss. His car felt much better when he went to a bigger converter to tighten things up, and it picked up MPH on the track, too.

I measured from the pump drive down to the inside of the pilot then pump drive down to ring gear then ring gear to pilot outside with the vert on a counter top.I think .020 was min spec.
ps;measure from the bolt lug to the top of the pilot with a straight edge on the vert for pilot ht.[about .625"]

Another question; "tight" meaning less span between the upper and lower lock-up specs?

So maybe for us, like 2800-3200?

Thanks, Joe

If I were buying it, I wouldn’t really want them to try and “match” the converter to the combo.

The conversation would be more like, “make me a 10” unit as tight as possible”.

Well, it's kind of subjective. "Tight" to me means it still drives nicely on the street and responds well to part throttle below the flash stall speed. "Loose" to me means the car feels "slushy" and doesn't respond well to the throttle below the flash stall, even if it locks up well at WOT. It's a streetability thing, I suppose.... and probably a tough thing to achieve for builders of fairly high-stall street/strip converters.

Thanks, Fast, I think we're getting closer here.

Joe

FWIW, my last three converters as the car evolved:
1. Coan 11" Pro Street spec'd for about 3000 stall (pretty close in my car); only had about 4% slippage, but Coan rated it for max of 500 HP, IIRC. Worked fine when car was low-to-mid 12s, then lost its sh!t when I put in a new engine that pushed the car well into the 11s

2. J.W. 10" 3800 (they offered a 3800 and a 3400 version); flashed about 4000, but slippage was 12% and it didn't drive well on the street... very "slushy"

3. Dynamic 9.5" advertised as 4200, IIRC; flashes to about 4500 in my car and slippage is about 8%; drives much better on the street than the J.W., and picked up .2 and 2 MPH as well because it didn't slip as much

4. Dynamic sold my friend Mike on a 9.5" for his car (the one I described in my previous response) and his experience w/ it was a lot like mine w/ the J.W. He switched to something much less track-oriented and was much happier.

"You pays your money and takes your chances".

I had Chris at Continental (SP?) Converter make me a street and strip 10.0 inch converter based off of the dyno sheets for my first 505 C.I. pump gas low deck stroker motor with a set of ported big valve 906 heads and a stock 440 type six pack set up , it had 9.25 to 1 compression and made 612 HP at 5500 RPM with 644 Ft. Lbs. at 4500 RPM.
That converter would push the front tires through the staging lights at 2300 RPM foot stalling it in low gear(2.77 ratio), it would flash around 4400 RPM in high gear, I ran that converter on the street and strip for several years before breaking it beyond repair I replaced it with Turbo Action race 8.0 inch made for a SS/AH car that had not been ran, that converter at the track ran .2 quicker and 2.0 MPH faster in the 1/8 mile than the 10 inch did and it drove a bunch better on he street.
It would foot stall over 3400 RPM in low gear and flash stall right at 5200 RPM in high gear at a slow roll It drove really nice on the street at light part throttle and loosen up with more throttle I wouldn't hesitate to have Paul at T/A make me another one just like that
Converters are not a science that all converter makers have down pat yet Some are way better on getting them right than others Not all of us like the same things, just like camshafts, carbs and intakes, huh Brad

have one built for the car, you will be much happier.

http://www.tcsperformance.com/performance_converters/

My conversation with Lenny at UCC was that I wanted as tight a converter as I could get given the limitations of a 9" converter dealing with gobs of torque. He said this is as tight as he can get a 9".

He also recommended that I run the thicker John Deere Hy-Gard rather than ATF. And not the generic brands of hydrostat fluids either. It seems that the Hy-Gard has the standard and then has a low viscosity version. Most generic brands tend to be the thinner viscosity. And, of course more viscosity helps tighten up the converter. I also run a big tranny cooler to help all it can. Hy-Gard is roughly equivalent to 10w30 oil. I have thought about trying some 50 or 60 weight oil mixed with the tranny fluid, but I just haven't gotten around to it. I do have some ATF in there just to give it some color, making it easier to see on the stick.

As for the snout, I just lightly touched up the snout and crank until it would go together.

Which is why I’d be talking with someone about a little bigger unit.
9.5” or 10”......... probably a 10”.

My 9.5 Dynamic works nicely in my 63 behind my 493. It drives great all the time as I can cruise the back roads at 2200 rpm and I don't notice any slippage just like when I drive the highway at 60 mph it just drives great all the time. It flashes to about 4000 or so at the track and works ok for my mild street car. I can hit it at any rpm when driving it and its always right there and just never seems to sound like its slipping any to me at any speed I drive. Its been in my car since 2006 as it was actually built for my old 440 but I am very pleased with it. Ron