need opinions on which converter and controller

[jjump59]

Going to run a 4l80e behind a gen 1 421 sbc, about 550 hp in my 69 Camaro and wondering which converter and controller you guys are running or would suggest. Cam is a comp solid roller xr280, has around 550 lift and 280 duration, they think it needs a 2800 stall but i'm not sure we need that much. thanks for any help you can give.

[rjsjea]

I would call Twist Machine for both.....he could set you up with both

http://twistmachine.com/shopping/index.php?main_page=index&cPath=5&zenid=2864c461e6eb7c839ce73b9a3ab456d9

[jjump59]

i will probably call them but i'm looking for opinions from people that are running them, Llooks like they use compushift and there are others out there. I'm guessing from the response it's not a very popular transmission in a PT car.

[Steve Chryssos]

Maybe they're not popular, but the 4L80E is a very smart choice in terms of torque capacity per dollar. Your engine combination should be making good torque by around 2500 rpm. Some might think that your solid roller is "big", but it's actually a good match for your big inch small block. The added displacement will make your cam feel smaller.

Stall speed is directly related to input torque. And input torque varies with load and rpm. On a drag car, peak torque is critical to making the most of a standing start acceleration run. No sense leaving the starting line at 2500 rpm when more input torque is available at 4500 rpm--assuming available traction. But on a pro-touring car, load and rpm vary greatly. Input torque varies in kind. Power needs to be applied at part throttle when powering out of a corner (a smaller amount than that drag scenario). It also needs to be available for light throttle "touring" as well as for standing start acceleration.

Comp lists the operating range for your cam as 2500-6500. Operating range tends to vary with displacement. More displacement yields a lower operating range. So your 421 might start making torque a few hundred rpm sooner than a typical 383. You will then see that they list stall speed as slightly higher than the beginning of the operating range. That might lead you to lower stall speed in kind.

Seriously? It's kind of hard to go wrong with a big inch small block. Just spend some time pinpointing your real world intended usage for the vehicle as percentages. i.e. 70% touring, 10% drag, 20% road race. If you will spend a ton of time in overdrive at 7% throttle angle, lower the stall speed to 2500-2600. If you will spend 50% of time at the drags and the car can hook, raise the stall speed.

The only other consideration is whether you will be buying an off the shelf or custom converter. Your cam specs list 350-400 cid. But you have a 421. Same holds true for off the shelf converters. They're all tuned for 383's. Since stall speed is tied directly to input torque, that off the shelf converter with the 2800 stall label might stall higher behind your 421. So you might want to choose a lower "advertised" stall speed to hit the 2800 rpm target on your 421. A good custom converter, on the other hand, will be tuned for your car, your cam, your displacement, your gear, your final drive--and most importantly, your driving objectives.

[jjump59]

great response, sounds like your pretty much in touch with things. i was just getting on here to get your number and call. thanks again.