Hi-stall Converter(?)

[Pope Downunder]

I've removed the motor and box from the pickup to make way for the new engine.  The TH350 box is fine, with less than 7000 miles on it from a rebuild.

The torque converter is currently stock.  The take-off has always been sluggish, and it will take-off even at idle, but bogs a little if floored.  I am thinking of putting in a converter with a slightly higher stall, but I've never had one before, and I'm not sure what to go for, and what to expect.

I have the mild 313CI SBC, 3.5:1 diff, 28" tyres and a wet weight of just 2790lbs.  I'm looking for all-round driveability.  It is street only use.

'Dominator' (http://www.dominatorconverter.com.au/) recommended I go for a heavy duty 2500rpm unit; but I baulk at the $430AUS price. I realise all such things are a compromise between take-off and cruise, but I reckon if it slipped at 50mph cruise, I'd be a problem for me.

So, if I ordered one with 2000rpm stall, would that be worthwhile, or should I just stick with the stocker?  secondly, if I go for the lower stall, is it really necessary to go for such a heavy-duty unit, or would a modified stocker be a better proposition?

[Sean]

I bought a 2400 stall (a blue one) for my truck a couple years ago and it won't stall what its rated. If I flash the throttle it will jump to about 2000, but thats it. I bought it because I had a 292-.505 Cam in a 350 at the time and it idled at 1000rpm. I figured that would keep it from pulling against the brakes so hard at the stoplights, but it didn't seem to make any difference.

The engine thats in it now is a 10:1 350 with the ZZ4 roller cam, which gives me a lot more low end grunt than I had before. The Convertor still won't stall what its rated. Same thing actually, it will flash to 2000, but other than that it doesn't seem any different than stock.

[purplepickup]

I'm curious about this too.  It seems like each car reacts different depending on weight and how the engine is built.

I put a 12" B&M Holeshot 2000 in my truck and if I nail it the rpms jump to around 2700.  To try something a little different I got a red one from where Tony works that was rated at 2500 and it seemed too loose for me.  Rpms would jump to around 3200 when I hit it hard.  It was great for racing since my engine has a fairly high duration cam but I didn't like the way it reacted on the road.  Maybe if I'd have driven it more I would have gotten used to it. I was seeing a little higher trans temps too.  I went back to the B&M 2000 for driveability.  

It would be nice to have the driveability of the 2000 but the acceleration of the 2500.  A guy at work gave me an 11" Holeshot 2400 that I might try next time I get enough ambition to change converters.

[rumrumm]

I had a 2400 stall converter in my roadster running a 3.36 rear end. It slipped enough at driving speed so the rpm's were comparable to having 3.70 gears. It made it nice for cruising around town and on the highway at 55 mph; it idled nicely at stoplights which a stock converter would not allow.  But it was miserable on the interstate because I was turning 2900 rpm at 65 mph. Any faster and the blower would start making boost and my mileage would go to crap. That is why I built my new car around a 700R4 overdrive with a 2400 stall lockup converter. Hopefully,  that will solve some of the drivability problems I encountered previously.

[Pope Downunder]

I'm curious about this too.  It seems like each car reacts different depending on weight and how the engine is built.
...snip...

BTW, is yours running a TH350?

Thanks guys; that has 'sort of' confirmed my concerns.  I think I'll go for a lower level, like 2000rpm, and not the expensive HD type.  Too expensive for trial and error.  Most of the 'of the shelf' units are probably designed for 350s, and cars that are heavier than a street rod.  With my smaller engine (313ci) I will get one made to spec.

[av8]

I'm curious about this too.  It seems like each car reacts different depending on weight and how the engine is built. . .

Differences in specs, even within the same engine architecture, seem to make a noticeable difference in how the converter  performs. For example, the "shape" and location of the effective torque curve of a 350-cid SBC can be moved around quite a bit, up or down, depending on camshaft specs and those of the intake and exhaust tracts. That's the beauty part of building motors, making them do what we want them to do when we want it.

I'd love to see the RRT get involved in a board "seminar" on this sort of issue, and the overall matter of engine/drivetrain building, taking into consideration not only the needs of the performance-oriented street rodder, but also those who want to cruise with the comfort, ease, and economy they enjoy in their civilian cars.