Stall Converter

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pressedham

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Could someone please explain exactly what a stall converter does.
I have a 340 done up hooked to a 727 with a shift kit and 355 rear.
Have no botom end but does chirp when shiftin into second.
Someone suggested a 2800 stall.
What will this do for me.
Still learning.
Thanks
 
Torque or stall converters multiply torque. When you start building up a motor your moving the power band up in the RPM range. Adding a "looser" torque converter help the motor get into your power band faster by "flashing" over the lower rpms.

For an example my car has a 8" torque converter that will "stall" to 3000 rpms and "flash" to 4000 rpms. This helps the motor pull harder because it doesnt need to rev from 1000rpms to 4000rpms. It starts pulling from 4000rpms were the motor is making more power. Thats very helpfull if your using a larger then stock cam.

A loose converter is one that has a higher stall speed. A tight converter is one that stalls lower. Even though my converter is looser then stock its considered tight for an 8" wich often stall as high as 5500rpms.

Stall speed is the amount of RPMs a converter will let the motor rev to against the brakes without spinning the tires. Hold the brakes hard and bring the RPMs up slowly without the tires spinning. thats your stall speed. My will stall to over 3000rpms. Sticky tires help.

Flash is how high the converter will let the RPMs jump when you nail it. The best way to check a converters flash rpms requires a full manual valve body. Place the trans in third and while rolling at about 10 or 15mph nail the throttle and watch were the RPMs jump to. Mine flashes around 4000-4200rpms.

How big of a cam do you have ? Even the stock 340 cam will like more converter then stock.
 
It sounds like you may have put too much cam in that 340. With 3:55 rear gears you should have some bottom end, but if you don't, a higher stall speed converter should help. What type of vehicle do you have this 340 installed in? What do you have for an intake manifold and carb combo on there? A poorly matched intake/carb/cam combo will definitely kill off your bottom end power. By the way, did you degree the cam or just install it straight up with the marks on the crank and cam gears? If you can chirp the tires going into second gear, it sounds like your engine is getting into its power band about there, but not off the line. Oh, and welcome aboard from another Canuck - you'll like the site and the people here. :)

Sid
 
As Adam said, raising the stall speed will let the motor get into it's power band quicker. If the motor make all it's power from 3500-6000rpm, and the Torque Converter stalls at 800rpm, then the engine will seem to bog when you mash on the gas. But if you slap in a TC that stalls at 3500rpm, the motor will very quickly rev to that rpm and be right in it's peak power range. It's similar to rev'ing the engine and dumping the clutch on a manual transmission car.

And there is more to TC's than just stall speed. You would be miles ahead talking to a reputable TC manufacturer to select one (or better yet custom build one) that matches your exact engine/car combination and driving habits. NEVER listen to recomendations from your buddies when it comes to selecting a stall speed.
 
Thanks for the info.
It is a comp cam (dont have the specs) edelbrock intake with a 780 holley
engine is 30 over. Sits in a 68 cuda fastback.
Right now if i hold the brakes its impossible to get rpm in engine. So by switching out to a stall i should be able to light up the rears, yes.
 
pressedham said:
Thanks for the info.
So by switching out to a stall i should be able to light up the rears, yes.
Click to expand...

Yeah, but then you'll be asking how to get it to hook. :tongue3:
 
Its going to be real hard to pick the right converter with out knowing the cam specs.
 
Try A Hughes T/c. Tell Then What Stall You Want (probably 2400-2800) And They Will Give You One With A 340 Weight On It And Made For Your 727. And For This You Do Not Need Cam Degree Info. I Jusr Did On E For My 360 And 904 Setup. They Will Run Some Where In The 300-400 Range. Jeff
 
Try A Hughes T/c. Tell Then What Stall You Want (probably 2400-2800) And They Will Give You One With A 340 Weight On It And Made For Your 727. And For This You Do Not Need Cam Degree Info. I Just Did One For My 360 And 904 Setup. They Will Run Some Where In The 300-400 Range. Jeff
 
What converter did you end up putting in there? I'm still trying to decide which one to install in the Valiant when it comes off the rotisserie. My combo sounds quite close to your setup for engine, trans, and gears.

Sid
 
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