More build questions

[nandoz]

Since it's still freezing cold here, I am penciling out some math on my build. I'm trying to nail down a torque converter. The way I figure with a 28" tire and 3.50 gears I should be turning 2300 rpm+/- at 55mph. My cam is advertised as 2250-6000rpm. The question is: should I be looking at 2500-2600 stall speeds or 2000-2400. Maybe it's splitting hairs on a street car, but my budget is tight, so I want to get this right the first time. Also I don't want to be driving to work with the converter slipping the whole way. Where I live all of the roads are 55mph speed limit, so I am using that as my baseline.

[Drew Pojedinec]

I know this isn't exactly what you've asked, but a custom convertor from PTC or Broader, etc is around $500 for a street car.

If you tell them EVERYTHING, they are pretty darn good at getting it right.  I put convertor and camshaft choices really at the top of the list in getting the most out of a vehicle for your usage.  As such I couldn't imagine using an off the shelf part for either of these applications.

[jayb]

I'd be looking at a 3000+ stall speed converter, to get the engine up into the powerband on acceleration.  The stall speed does not have to be lower than your cruise RPM; any slippage will be so small that it won't be noticeable at cruise speeds.  On acceleration, when you mash the throttle the RPM will flash up to somewhere around the stall point; you want that to happen where the engine is starting to make really good power.  Too low a stall speed will make the engine feel doggy when you mash the throttle.  It took me a while to learn this; I was really worried about running a 4500 RPM stall converter in a 700 HP FE on the street back in 2005, but the car ran 2500 miles in a week during Drag Week that year, and was flawless on the road cruising at 2600 RPM.  Now I'm comfortable running over 6000 RPM stall on the street, for a more radical engine. 

Let a good converter company guide you, as Drew suggests.

[fryedaddy]

i have been running a 3500 on the street for many years now.i never notice any slippage except when im coasting down a big hill and tap the throttle ,but if you hold the brake it will sit still and rev over 3000 without pulling too hard.

[nandoz]

Thanks for the replies. I have heard plenty of good about Broader Transmission, we will see what they have to say.

[Falcon67]

Error on the "high side" for a bit better performance.  3.50~3.75 gear with a mild cam is usually an 11" unit with 2200~2400 stall.  Fine for street, drive like anything normal.  A tight 10" 3000 stall would not be much different, really.  Converters react to engine torque, so a 10" 3000 that errors on the tight side could flash 2800+ depending on the torque produced by the engine at that RPM.  Bigger cam, lower flash (less torque).  This is why you give a good converter builder ALL the specs for the car - everything including white or black sidewall tires - and if possible a dyno sheet, along with your real intended use.   And where you live - a converter set up to run well down in San Antonio is not going to work near as well in Denver.