Some of the swap parts include...
Some of the swap parts include the torque converter, the dipstick and tube, the flexplate, the driveshaft yoke, the transmission crossmember, and the auto shifter.
Prior to the transmission swap, we researched the fitment of the present BBK long-tube headers with the automatic gearbox. All of our sources pointed to them not fitting, so we put in a call to Kooks Custom Headers in Bayshore, New York, for a set of its 131/44-inch stainless steel long-tube headers and a 3-inch X midpipe. We'd heard Kooks was the only game in town, and talking to George Kook Jr. confirmed that these headers would indeed fit the auto despite the larger-diameter primary tubes.
Watson had the headers ceramic-coated at a local shop prior to installation. We also had planned to dyno test the Bullitt before and after the transmission swap, and after borrowing an external fuel pump to replace the one that quit on us on the dyno, we were able to get a baseline figure of 622 rwhp and 536 lb-ft of torque. Post transmission swap, we saw the numbers dip to 577 rwhp and 494 lb-ft. That comes out to a little less than 8 percent loss, or about what the BC Automotive guys had predicted.
Dyno numbers don't tell everything, though, as we expected the automatic to pick up in the quarter-mile over the stick-shift box. The best run on this motor and TKO tranny combination (Watson had a standard block 5.0 modular previously) was an 11.076 at 127.80 mph with a 1.551 60-foot time in cool weather. This was backed up with a tire-spinning 11.30 pass.
On the control side of things...
On the control side of things are the shifter and shift-lock cables, the ECM and transmission harness.
After installing BC Automotive's 4R70W, the first pass out was an 11.15 at 118 mph. This was an easy, get-acquainted pass (1.79 60-foot) that we followed with a more aggressive launch the second time around. On pass two, we saw the short time drop to 1.50 seconds, and shortly thereafter the Traction-Lok went and the car veered sideways. That was the end of the day for us, but things were looking hopeful, as a three-tenth reduction in the 60-foot time is usually good for six-tenths at the other end-and in our case, possibly a 10.50 elapsed time.
Not one to give up easily, Watson had the HP Performance crew install another 31-spline limited-slip unit. This time, a 1.68-second 60-foot time netted an 11.17 at 121 mph. This was followed by several more low-11-second runs-something unobtainable before the swap. The car's ultimate track potential was never realized in this test, and we are looking into a possible tuning issue and the need for a higher stall speed converter. Aside from that, Watson gushed about the automatic's much improved street manners.
"Unfortunately, the first aftermarket clutch started failing at the higher power levels," Watson says. "I decided to upgrade it, and it worked well at the track but was not as street friendly as I would have liked. You would have to leave a stop light at higher rpm and slip the clutch more to keep it from chattering. It took a lot of fun out of driving my car around town, and being able to enjoy the car on the street is important to me.