It's a candy store out there for Porsche 951s when it comes to performance upgrades. So many tuners to choose from, so many different parts, and I would test them all if I could. But, because of obvious limitations, I've got to be somewhat selective, and that's why the Porsche has so far received a Kokeln Stage V turbo, feeding the motor with copious amounts of air. At a moderate, 91-octane-friendly boost level, the car was already seeing 270 whp with the stock exhaust system in place. When Kokeln founder Dwain Dement finished tuning the car, I decided it would be best to drive it with a very mild boost level of 7.5 psi, good for a modest 170 whp and change-at least until I got a more free-flowing exhaust system installed in order to limit heat-soaking backpressure.
Next up was an aftermarket exhaust system, so I gave Performance Products a call (a major distributor of B&B Performance exhausts) and ordered its B&B header and cat-back exhaust system. B&B made no performance claims about the header system and said that the header was designed to be primarily just a factory replacement product. Apparently it's a common thing to crack headers on these 951s, especially the early '86 models, as the header systems did not come with a flex joint. B&B's header system features a slip-fit flange to avoid cracking, making it essentially a three-piece system and is made from 304 stainless steel.
When I looked inside the tubing, I was a little concerned to see what appeared to be two pipes that were welded together. I wasn't sure how it would affect flow, but as long as these headers flowed similar to stock, I thought they would be good enough to replace the factory units.
The car went to Precision Motion in Riverside, Calif., for the install. This family business has been around since the mid '70s servicing Porsches, including building several race motors that were run year after year at Daytona's 24-hour race. Now owned by long-time Porsche fanatic and mechanic Don Kravig, Precision Motion was my choice to get more work done on Project 951, starting with this exhaust system.
Luckily for me, Precision Motion has a loading Clayton dynamometer in the shop. Although, at the time, Don's computer software running the system didn't print out graphs like I'm used to seeing by the more widely used Dynojet dynos, I decided to test the headers anyway to see if at least the same power was sustained, given a certain constant load on the motor. How Don did this was by loading the car at wide-open throttle in fourth gear at selected rpm levels, and taking down the registered horsepower number the car was able to maintain before it couldn't accelerate any more and fell off-sort of like testing the car in an extreme, uphill situation. To get a proper test, we first had to get a new baseline with the factory headers still on, since Clayton dynos are notorious for spitting out ultra-conservative numbers when compared to a Dynojet.