I've always been a nitrous and N/A guy and going bigger on the converter stall never left me unsatisfied. This is my first boosted application to match a converter to. I've already decided that i'm going with Pro Torque, so I'm not looking for suggestions on who to go with. The combo

10.5:1 408 stroker
PRC as-cast 257cc ls3 heads
3.6 kenne bell @14-16 lbs boost
226/246 .629/.629 118+4
1 7/8 headers, dual 3.5 exhaust
4l80e with trans-brake
3300 weight?
34x22.5 tires
3.55 gears (willing to change)

the options for converter is 2800-3200, 3200-3500, 3500-3800.

 

Circle D, 3500 to 3800. Oops looks like you already have a brand picked out but yeah at least 3500.

 

Depends upon goals. With a big inch motor, baby cam, and low end torque monster blower you will not “need” something in the 3500 plus range.

Guy I know has a 421 inch lsx with a twin screw in a heavy car and has good success with a 2800 converter.

Different needs than a 5.3 with a turbo.

 

Honestly I don't think this is a pick one and done deal.
Intended use will play a role and the transbrake in the 4L80E says you intend to race it so a higher stall would probably be the way to go.
With that said, I would lean on Pro Torque to give you an idea of what stall to select, then be ready to pull the converter back out and have them tweak it for optimal performance.
I had to do just that with my Circle D unit (they've been great to work with) as each combo is a little different and might take a couple tries to see what it likes.

 

This is something built specific for the application. I'd call the manufacture

 

the converter is on order. I went for the middle 3200-3500 and we can make changes from there if we think it needs it.

 

Did they spec it for the blower? For a positive displacement blower you really want a tight-ish converter, They make great low end torque so as long as your stall is above where you might have cam related drivability issues then your good. As someone else mentioned, It depends on your intended use.

 

It’s got a 4l80 so it will only be changing gears twice down the track but the tighter the converter, the more the drop in RPM’s upon gear change so although the positive displacement makes low end torque, there is still the upper range to consider when shifting gears.

 

Dropping down to 5000 rpm on the gear change isn’t as big of a problem with a big inch motor with a positive displacement blower. On the extreme end that would be a big deal with a 5.3 and a centrifugal. Each combo has different needs and the people building his converter know this. No sense in having massive off idle torque if you’re blowing through it with a loose 3800 converter.

 

Agreed, it’s just hard to know what his engine performance will be like. Definitely don’t want to blow through the converter but would also hate to see a 6800 to 4800 drop in gear change. He will have to play with it, who knows maybe a 3k stall would be all he needs.

 

You can always look into locking up the converter once you're moving too.
I know several guys that have a triple disk unit that locks up the converter in 2nd and 3rd at WOT.
They say it drops the RPM down 300-400 rpm and the car just flat out rips when it locked, turbo cars though so that may change things a bit.
There's some transmission mods that come with it but might be worth looking into.

 

I'm also going to a 4.56 gear from the current 3.55. 4.56 gears on a 33" tire is basically equal to a 4.10 on a 28" tire.

 

I think you are underestimating the difference a PD blower makes, Think of NA big block power and rpm range. Turbos make mid to upper end power and carry it until redline where the PD blower engine makes better low end grunt and levels out sooner, They also make more heat the faster you spin them so it's better to optimize low to mid range power rather than top end.
The converter you ordered might be perfect for you the only way to tell is to run it.