Hope I’m not butting in here – Marc M. asked me to come over and say howdy, and perhaps offer a little insight on torque converters, as we’ve been having this same discussion on one of the bronco lists…
There are a few very important components of TC selection:
-Stall: higher stall speed is equivalent to dumping the clutch at a higher point in a manual - getting you in your powerband as soon as possible. higher stall = harder launches, but with the expense of generating more heat and being less "tight" at lower rpms. Stall should ALWAYS be tailorer to your cam and powerband to the best of your knowledge.
higher stall is not always better, but lower stall is not either! i had a 1400 12" stall that i HATED! it felt like having 150 less horsepower, and didn't really have a whole lot more grip down low. i run a 2200 stall now, with the higher STR, it feels just as tight down low, but boy does it scream when you step on the go pedal! When I’m in 4 low, it pulls HARD against the brakes, and even in 2H, it pulls pretty hard. That’s a function of the STR, not the stall.
-STR (aka torque multiplication factor) - this is how many times the converter multiplies the torque for you, stock is usually around 1.7:1, this will go up exponentially w/ cost - my current converter is a 2.7:1, anything over 2.2-2.5 is good. anything over 3.0 and you lose a lot of efficiency and build a LOT of heat. another word on STR - the reason that most “car” guys don't get higher str's is that they can't get traction - a problem that not many of us have w/ 2000 extra pounds, 12" wide tires, and a suspension that lends itself to weight transfer rather easily. There’s a pretty good explanation here if you want to do a little reading:
http://www.converter.cc/technical_discussion.htm
-efficiency - ask about it - most stock are above or around 95% - mine currently is 96% - the less efficient, the worse gas mileage you'll get, and the more heat you'll build.
other things to ask about:
-how are the fins attached? furnace brazed is good.
-torrington bearings or just thrust washers? torrington are good!
-steel or aluminum stator? steel is very good, but expensive.
-anti ballooning plate - good to have, useful for higher rpms.
-clutch material (for lockup converters) - anything other than stock is good - many have a proprietary material, others use carbon ceramic, etc.
A few words about off-the-shelf converters - both TCI and B&M are considered "off the shelf" converters - not terrible, but not great… it's comparable to ordering a custom cam vs. an off the shelf cam - you might make 15 hp w/ the OTS cam, but 30 hp w/ the custom. of course custom always costs more money. ;-)
i know of a few people who have run b&m, tci, and art-carr converters, that when the converters came apart, all those nice parts from those nice converters floating in the lines took out their trannies as well. i had this very experience w/ art-carr's premium $500 torque converter - which took out my $1000 transmission when it decided to come apart driving up i-15. of course they were in the course of moving to TX, and had lost my record of ever being a customer... they were very happy to sell me another for a $100 discount. :-(
i know of many others that never had problems... will it happen w/ yours??? probably not, as most of these were higher HP applications. but are these premium converters? no. and speaking from the viewpoint of someone who apparently can break ANYTHING (and always does), i always prefer the premium product over the generic.
Who do I recommend?
Nobody for converters locally – although for transmissions there are a few decent GM builders local, not any ford or mopar that I know of
My recommendation list
First, NOT art-carr! The horror stories are endless, and for some reason, everyone keeps buying from them! You were warned…
trans-king in texas is reputedly good....
i've had VERY good luck with precision industries, but they are typically relatively expensive.
Continental and TCS are reputedly both good, although i've never used either firsthand.
i use midwest converters with great luck for my gm stuff (700r4), don't know if they make any early ford, but they make all late model stuff.
yank also makes great gm stuff, not sure if they make early ford.
midwest:
http://www.raceconverters.com/
level 10:
http://www.levelten.com/
tcs:
http://www.tcsperformance.com/
continental:
http://www.txchange.com/stalltc.htm
precision:
http://www.converter.com/
yank:
http://www.converter.cc
you'll have to call any of them - all the websites don't have all the info on them, and in most cases, i have all converters built to specific specs rather than a premade model that they offer...
HTH!
