November 2012 Chevy High Performance Q&A

Power Tour Leaves

Kevin McClelland Sep 20, 2012 0 Comment(s)
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Now back to your transbrake. From the specs of your engine build, it sounds like you need more torque converter stall speed. With your cam specs, single-plane inlet, and 215cc runner heads, we bet your torque peak is in the 5,000-rpm range. If you can’t foot-brake the car past 3,000 rpm, we’d bet the car is pretty flat off the line and really starts pulling. You didn’t mention what your miles per hour was in the lights, but 11.40 calculates out to approximately high 114 mph. Yes, a transbrake will possibly give you a few more rpm if you can’t hold the car with the brakes above 3,000. The main thing with the transbrake is that you are going to want to run a two-step rev limiter so you can set a launch rpm. This will allow you to adjust your launch and vary your reaction times.

Now for the downside of a transbrake; if you don’t control the launch rpm you can really be hard on parts. If your rearend and axles are not up to the task of getting hit at full torque load from a standing start, you’ll find the weak link. The transmission must be built with higher-quality parts to also withstand the added punishment. Finally, the torque converter must be reinforced to prevent “ballooning” as you sit at full throttle against a locked transmission. Now, if you can control your aggression against your parts, you can run with more pedestrian components. For instance, in our ’80 Malibu wagon we’ve got an 8.5-inch corporate rearend outfitted with Strange gears, spool, and 35-spline axles. We’ve added an LPW Ultimate differential cover with axletube braces. This covers most of the weak links in the rearend, but we still only hit the rearend with 3,000 rpm off the transbrake, even though the converter at full stall will go to 4,500 rpm. The other reason we keep the rpm under control is that we’re running a B&M Nitrous Holeshot 3,600 10-inch torque converter, which isn’t really made for transbrake use. If we keep the rpm under control, the converter doesn’t know if we’re leaving off the foot brakes or the transbrake.

With your combination, we’d recommend a Powerglide trans with a transbrake. They take less horsepower to turn, and the transbrakes are much simpler than converting a TH350 to a transbrake. You may think you would run slower with the two-speed. We actually went about 0.08 quicker with the Powerglide than our low-gear (2.75 First) TH350 trans, and with more consistent 60-foot times. You can swap out the input shaft for a Turbohydro spline input and use your current converter. If the dollars will allow it, we really recommend the B&M converter we’re running. It gives you great stall speed and limited slip at the top end for good mph for a 4,500-stall converter.

The transbrake will help you be much more consistent with your reaction times. Your 60-foot times will get tighter, and you’ve only got to move one thing to launch instead of two! Good luck with your Camaro, and we hope you find your extra nitrous performance. chp

Sources: bmracing.com, lpwracing.com, strangeengineering.net

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