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1991 Pontiac Firebird Formula - Dyno Diagnosis, TPI Style

What do you do when the strip numbers don't jibe with the hardware?

Photography by Terry McGean

'We thought we were onto something good back when we decided to turn this '91 Formula into a multipart series. It seemed like the thing to do, since we could hardly believe cars like this could be bought in good shape so cheaply ($1,500). A Tuned Port 350 F-body was a coveted car in its day, being among the first cars out of Detroit since the early '70s that seemed sort of worthy of the term musclecar. Plus, chicks were into F-bodies back then.

But today, Detroit has produced much faster cars, TPI speed parts are still as expensive as they were back in the '80s (only now they're being discontinued), and girls refuse to ride in this thing. Add to this the fact that simply keeping the 'Bird running has at times been a challenge and to this point, the speed returns have been modest at best, and our third-gen project starts to lose its luster. Yet in spite of our troubles, we've managed to maintain some optimism, largely because we know these things can really move if handled properly. We also know that it's easy to spend money and effort on stuff that doesn't help, and it's probably better for us to make the mistakes than you.

RecapFirst up was repairing what seemed to be minor glitches-we thought a new EGR valve and maybe an ignition tune-up for good measure would have the Firebird ready for baseline numbers, but as we outlined in the Aug. '05 issue, a series of failures made preparing for baseline runs a project in itself.

Persistence paid off, and we did get the Firebird sorted out, paving the way to move into the speed parts. That's where SLP stepped up, providing new high-flow intake runners, a cold-air kit, smog-legal shorty headers, a Y-pipe, and Cat-Back exhaust. The dual cats were also replaced with a single, 3-inch unit from Random Tech. With these alterations, the Firebird picked up more than three-tenths from our baseline of observed 15.0s at 91.23 mph to 14.66 at 92.82; that corrects to a 14.19 at 95.9 mph using the factor for LACR's altitude-strong for a stock L98 F-car, particularly one with 150K. If nothing else, our test-mule was healthy. It seemed that if we could get the 60-foot times under 2.00 seconds (from 2.20), we might just break the 13s.

To that end, the next move involved swapping the stock torque converter for one from B&M with 10 inches diameter and a 3,000-rpm stall speed. For our efforts, we received a 1.98 60-foot time and a 14.12 at 92.43 mph (corrected). The short time was better, though it still needed work, and while e.t. picked up appropriately, the trap speed slipped back a lot. This is where things started to get weird.

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