What size and stall speed do you guys think i need behind my 12:1 572 Hemi street/strip deal? I have been running an 8" Dynamic 5400 stall behind my 511 12.5:1 wedge on the street without issue. I'm not afraid of stall speed and dont want to give up anything and drive it on the street. I have been told by a few that most under stall their Hemi's. Been told Hemi's n/a dont make the torque of an equal wedge, sounds like they need more stall. Not sure, what do ya think?

I would think either a 9.5 or 10.0 inch custom built converter would be my choice, have FTI or Turbo Action help you decide and build it for you

I agree, I’d call Paul Forte at Turbo Action and see what he says. I know Rick Allison doesn’t build converters but he deals with Trans Specialties and Rick would also be able to give you good input on the size of the converter and stall speed.

I'm curious, why bigger than 8" behind a 572 Hemi? What will the 9.5-10" do that the 8" can't? Just trying to learn something.

I have a custom built PTC 9" 5600 nitrous converter behind my 528" Hemi and still street driven all over back and forth to work, go get ice cream, cruise nights, car shows etc.

I was using an old 8" ATi that was specified for an old 770 ish hp 528ci motor. The car ran great with the replacement 580ci wedge with 4:10 rear and we ran it for years.
I recently changed from 4:10 to 3.73, stall speed increased from 5200 to 6100 and slip from 7% to 20% at the finish line. no changes to the engine, just blowing through the converter. I now have a 9.5" converter waiting to be fitted. Get a new one spec'd to your entire combo, a good converter company will usually ask for as much info available on the combo anyway. HTH's

Look at it like you would at a boat prop.

Larger is more efficient at mid range and higher speed.

The smaller converter coupling point is at very high engine speed. Not conducive to good street driving.

That is a long way with just a gear change. I'm at 6% now behind my 511 which i estimate 680-700hp. Looks like i will need a brand new larger than 8" vert for the Hemi which should be between 800-900hp.

A lot depends on the torque curve and what you want to do with the car. A custom full on race converter could run a 9.5 inch core, stalled more for max et, and be loose, like 6000 stall. A car mainly driven on the street where you want a more responsive setup, might be on an 11 inch core and stall 3600. Your info provided to a good converter builder will provide him with info to build what will suit you.

9.5 here from ATI....works very well. Interviewed a lot of convertor makers before I chose one, and very few knew what to use for a 600 cube street car...ATI had no problem.

I use a 10" ATI Fuel & Blown converter in the TH400 behind my Hemi. It's an excellent converter for my application. My current engine is smaller than yours at only 477 CID, but it's turbocharged so it makes at least as much torque as the 572 that you're building, at the current boost level that I'm running. I mostly drive mine on the street.

The main difference between converter companies is the honesty and accuracy of their customers when they provide the power levels and vehicle info and the performance feedback after the converter is used. This library gets them close when they build you a converter.

I haven't had that problem yet but some hard core heads up racer friends have had to go the larger diameter race converters to make the car go faster by holding the motor better under WOT than the smaller ones would. The smaller ones will "blow through" instead of moving the car well at a lower RPM IHTH

Ok, I understand. Dynamic hit the stall I was asking for dead nuts on the 8” I have now. Gave them all my info and they gave me an excellent vert. Can drive any where and cruising the temp never gets over 180. 6% slippage at the track. So does everything well. Looking for something similar in manners.

Wait until you put the motor on a dyno and take that data to the converter guy of your choice along with a description of your car and how you plan to drive it.

Beware on dyno sheets and converter guys making you a good converter correctly off the dyno sheets the first time. Not all f them can do that

ATI 9.5" Fuel & Blown converter here also. 5000 stall with 572 Hemi 284 @ .050 cam, 4.10 gear, very responsive on the street and great footbrake launch at the track.

That's great. If you like what you got from Dynamic, I would contact them for their recommendation, if I were you. They may tell you to try what you have now or recommend something that's a better match.

I also think this is wise.

A good 10". I had Paul at turbo action redo a TA 10". I make 818ftlbs@4800, he had me give him the numbers off my Turbo Action 10", he said it was one of his good ones. I also had one of his 8" convertors but he said he wouldn't ever be able to get it right enough with the torque I made. Sent in my 10", it works perfect and he said it would handle 1000 hp.