I got a weird thing going on with a freshly rebuild 727 and a new 9.5" converter behinda 500CID with a roller camshaft making some nice horsepower! Street car, no race car.
First converter flashed at around 4000RPM although we expected it to be around 3000RPM. Otherwise the 727 shifted nice. (TF2 Kit, red racing clutches etc.)
The converter maker made a new converter and said it should get 800RPM lower flash stall.
The 727 was inspected after a few 1000miles and it looked brand new! All perfect!
Test drive a while ago with new converter showed 200RPM lower flash stall than before, although 800RPM were expected!
Converter builder really can't explain it and he said it's almost the tightest converter he can build in 9.5".

Now my question: anyone of you ever experienced somethign like that? Could it be a to low converter oil pressure? Something wrong in the converter lube circuit of the Valvebody? The line pressure can't be so bad since the clutches and bands looked like new when inspected and it was driven hard! But something really is weird here...

Any ideas?

You're worrying too much?
If everything is working well as far as driveability, I'd be happy that it is what it is. Just remember don't drive around in third gear low speed "up on the stall". People street drive 8" 5000 stall units.

2X

500 ci,roller cam and it's not a race car? If it were mine,I put that first convertor back in! No seriously,a 500ci motor will stall higher than a smaller motor.

the customer doesn't want it to stall this high... the cam starts to pull at 3000RPM, so 4000RPM higher is lost RPM.

No, it's not a race car... here tons of those 500CID cars drive around (illegaly since it's illegal to have more than 20% more HP than stock!) and none of them drives races (also illegal here or almost illegal at least)

But anyway, I am wondering what could change the stall besides the converter itself? If the converter pressure spring in the valvebody could do that for example?

I don't think it's a pressure thing , the stall is a function of the design of the internals of the convertor , convertor science is black magic. You might have to switch another convertor design .

what if the valvebody sends not enough oil to the converter like it happens in P? I would guess stall would also get higher / more slip?

By the way, it's an AUTOMATIC shift TF-2, no manual valve body...

Couple things; If you take off the return cooler line, it should be pushing out a good amount of fluid. Now you know the convertor is full of fuid.
Next, Why don't you just run a small(340) original convertor? Or something similar.

originaler convertor with 600HP? Why spend so much money on an engine to waste it on a piece of crap of converter? I installed over 60x 9.5" converters and I heck know the difference between a 11" stocker and a good 9.5"! It's day and night!

Sounds like a 10 or 11 inch might suit you better if you want less stall. Why are you convinced that you should have a 9.5? 3800 is pretty tight for a 9.5 behind a 500 inch motor. I dont think they could build a 9.5 with much less stall than that.

a 10 in converter would be closer to your needs with that much engine torque.. heck my stock 340 converter behind a mild 383 is pretty slippery... dan

You can build a 9.5" tighter than an 11"! I had 9.5" that stall at 2000RPM, it all depends what the converter maker makes out of it!
The 9.5" ist just the much better piece than a 11" stock converter...

But anyway, not discussing the size of the converter

So the conclusion is, the converter is the problem, not the trans/valvebody?

Its the converter. I had a 9.5 behind my 470RB and a 3.55 rear and I hated the slippping ALL the time. I replaced it with a stock 11.75 converter (around 1800 stall) and it will still fry the tires off the car. If you have a monster cam or a small block you need the higher stall but most high TQ big blocks will do just fine with a stock type stall and drive way better on the street.