In our last episode (Mar. '10) we dyno tested a slew of bolt-ons and the new Precision Turbo (#PTB305-5857) on our Grand National test car. With these upgrades we anticipated possibly breaking into the 12s (13.50 was the previous best e.t.), but the transmission began to slip in First and Second gear. This prompted a call to our friends at PerformaBuilt Transmissions for a rebuilt 200-4R, that could easily handle our intended power level, and a higher stall converter to help our hot, new turbo spool. From day one of strip testing we've needed a higher stall converter for a better launch to lower the e.t.'s, and when we removed the trans from Tim Cairone's Buick we discovered a remanufactured torque converter, which are typically a low-stall unit, probably installed during the previous trans rebuild. That explained why we could never build any boost for a good launch-our 60-foots were in the terrible 2.2 to 2.3 range! A typical 12- to 13-second Turbo Buick with the factory converter usually 60-foots around 1.8 to 1.9, launching with 5 pounds of boost. We needed a well-built trans and converter that could handle the torque and quicken turbo spool-up.
Given its unconditional guarantee (2-year with purchase of trans/converter, 1-year trans only-even if you race), we felt confident that PerformaBuilt would rebuild the trans using the highest quality parts that would have Tim's 200-4R outlast and outperform the previous regular trans shop rebuild. One nice feature is that PerformaBuilt doesn't require a core, so if you wanted to preserve your original trans for collector's value you could. Since ours had been rebuilt once, and the Turbo Buick trans is a much nicer and stronger piece than the other 200-4Rs, we opted just to have it rebuilt again. The present combination with the stock, unmolested engine (factory cam specs: 0.400/0.422-inch lift, 193/196 duration @ 0.050) is making peak torque at only 3,000 rpm-so theoretically we needed a converter with roughly a 2,600- to 2,800-rpm stall. PB recommended its Billet Race torque converter (10.5-inch, rated to 1,000 hp). They built us a 2,800-stall unit. With that we should have a trans and converter to hold up to our thrashings and further intentions of the build-up.
Unfortunately, our trans gave out right at the end of the race season at Englishtown, but PerformaBuilt got us our new trans in time before the snow hit and we headed to Atco Raceway where our friends from Tune Time Performance scheduled a test-and-tune day. Weather conditions were a pleasant 55 to 57 degrees with humidity at 60 to 65 percent and a steady 30.05 barometer. Tim mounted the 26x9 slicks and we pulled the GN to the line. We brought the boost to 5 psi but it crept up to 8 psi by the time we let off the brake pedal and punched the go-pedal. Wow! It was like being shot out of a cannon. The scoreboard lit off an impressive 1.65 60-foot time and the G-body crossed the finish line with a mind-blowing 12.28 at 108.11 mph. Two minutes later we made a second pass and ran a 12.35 at 107.80 mph to back it up. At that Tim jumped into his Grand National and hot-lapped a couple of mid 12-second passes. Totally satisfied, we had a bite to eat and made the 45-minute trip home.
Tune Time also provided us with some dyno time, so that we could demonstrate the affects of the new converter and fresh trans on chassis dyno numbers. Typically, an efficient high-stall torque converter (matched to the engine's powerband, peak torque to peak hp) will multiply more torque yet less horsepower to the wheels. This happens even to the quickest converter for the best e.t.'s in any given car. But it's torque that gets you moving down the track! On the street the shifts were firm, yet there wasn't that typical excessive slippage feel coming from having a high-stall converter. Turbo spool-up was quicker and 5-psi boost launches were easy. The street tires (255/60R15, stock heavy wheels) would now break loose when standing on it at a 35- to 40-mph roll. The car now felt now like a rocket-quicker response and acceleration than ever before, and we feel confident to reliably go for the 11s.