Can a line lock be used kinda like a transbrake to get off the line?

 

It can be, but it's basically the same as holding your foot on the brake, the more rpm's you give when stalling up, the tires will start to break loose.

 

Not really. You *can* put line locks on both the front AND rear brakes, activated by a common button. The procedure is to push the brake pedal down firmly, then while holding the pedal down, push the line lock button. As long as the line lock button is depressed, then the brake pressure is maintained. Assuming you are driving an automatic, when you press the gas pedal down, all slack in the drivetrain (tranny gears, driveshaft yokes, differential gears, shocks, suspension springs, engine torquing of the body/engine relationship, motor mounts, tranny mount, etc) comes out and the engine is pulling hard to overcome the braking force. Then you have the difficult task of simultaneously releasing the line lock and stomping the gas pedal the rest of the way down. The Transbrake on the other hand, has valving that applies the hydraulic pressure into both the forward drive and reverse drive circuits simultaneously, each able to counter each other and the car not moving forward nor backward as long as you have the transbrake button depressed. When you release the transbrake button, all hydraulic pressure is instantaneously routed to the forward drive. At up to that moment, all slack in the drivetrain is still in place. Nothing is preloaded in the driveshaft, differential or suspension. That's what makes the transbrake "leave" so brutal. If you have any weakness in the drivetrain, a transbrake will expose it in short order. If you engage the transbrake then stomp the gas pedal, the motor immediately rises to whatever the stall of the torque converter is capable of and stays there till you release the button. Though I never had a transbrake, I found that stomping the gas pedal from a dead stop at idle always got a better 60' than torquing up the car against the line lock. Leaving the line in the stated manner always rewarded me with 1.5x's and 1.60's sixty foots using MT ET streets on stock rims(11.1 @ 121 mph using a 100 shot)

 

interesting, so does that mean we have to use 2 line lock systems?

 

No, not at all. Just one on the front brakes is fine (and mostly typical). Only full time racers usually opt for front and back brakes.

 

Hmmm. If you could put a switch for the back then you could use the line lock for the burnout then flip the switch to hold all the brakes, stall up, and take from the line. Thanks for the info everyone. SLP and who else makes a good kit?

 

I'm just using 1 to hold my front brakes for the water box, so I'm not ruining my rears. I see no reason why you would need two, other than a poor man's transbrake. IIRC im not sure even if IHRA or NHRA rules allow you to install one on the rear brakes anyways. Then again at Test and Tune days they prolly don't check for things like that . I just hold the brake and preload the suspension and drivetrain to 1000rpm, then let her rip.

 

My insurance agent races (I know, oxymoron, right?) a '93 Z28 street car known as "Double Trouble" (200 shot of N2O and Procharger with 396 cubes of LT1 power) uses a TH350, vigilante 3200 stall, transbrake and front/rear Line locks. Like you mention, up till this, I'd never ever heard of rear line locks. My agent gets 1.2 and 1.3 sixty foots using ET streets. His car has full interior and weighs 3,550 lbs. I'll contact him later today to get his latest ETs/MPH but I think he runs 5's in the 1/8th mile. Just to verify utilization of the rear line lock, I used google and found some other users... Here's one from a Buick G/N board:
"One of the guys who runs a Buick board has a great launch tecnique. He uses
an MSD 2 step and a rear line lock. I can't remember what his convertor
stalls at, but we'll take 3500 rpm for this example. Thus, he can pretty
much bring his car up to 3000 rpm before it even starts to lurch and try to
move. So he sets his MSD rev limiter for 2000 rpm for the launch. When he
gets to the line and is staged, he applies the line lock to the rear wheels
(not fronts). This keeps them from turning. He floors the gas, which is
limited to 2000 rpm. Because the rear brakes are locked, and his convertor
will easily take 2000 rpm, there will be a chassis loading, but the car
won't try to take off. He uses a button to control the release of both the
rev limiter and the line lock (both to one button). Once one is activated,
so is the other. Once the button is released, the rev limiter will let go
and so will the rear brakes. His foot will already be on the floor, and the
chassis will already be loaded and ready to go. Once he releases the
button, the convertor will flash HARD and the car will launch. Essentially
he takes his feet out of the launch equation. It's all done with the
release of a button... I like that idea!
"