'We're stoked! And at the same time, we're still driving a 14-second white '91 Firebird. Though you voted on CarCraft.com that a guy could drive it without looking like a Nancy, and a girl could drive it and probably look hot, we'll still feel geeky until we can produce a 12-second timeslip.
So were on it. Using basic cooling and tuning steps, and opening up the intake and exhaust, we drove the 'Bird to a corrected 14.19 at 95.94 mph. Considering that the '88 Firebird that we built in 2001 ran 14.40 on nitrous, we'd say we're ahead of the game.
But there's more. When we bought this thing about two months ago, we were hoping for easy speed for low dough. But the car barfed every critical TPI-specific part that controls idle and driveability then got hot in traffic and stalled (see it on CarCraft.com). So we're behind a little in money spent but way ahead in speed. Our plan is to prove that you can go 13s in one of these cars without cracking the seal on the engine or opening up a bottle. Then later we will spray our way into the 12s.
Fuel System: Critical StuffWhat we didn't mention in the first story is that we solved a lot of problems by replacing the injectors and fuel pump. These parts are actually a lot more affordable from MSD and Holley now that the car is nearly 15 years old. The MSD injectors are 22 lb/hr and are listed as factory replacements. The Holley in-tank fuel pump will flow up to 255 lph at up to 110 psi fuel pressure. Good if you are going to spray it like we are. Just look at it like adding a new carb and electric fuel pump on an old musclecar.
First Run: 15.00 @ 91.23We could call this a baseline, but really the car wouldn't always start or run when we got it, so the baseline would have us burning to the ground at the top end of the racetrack after a 20-second run. Instead, by the first run we'd already performed a basic tune-up, replaced most of the fuel system and computer, and modified the cooling system with a cooler thermostat and electric-fan switch. You can expect a healthy car to run 15s at high altitude or mid 14s at sea level. On street radials we ran an observed 15.00 at 91.23 mph, or 14.519 at 94.30 using the standard NHRA correction for Los Angeles County Raceway.
Intake: Easy PowerThere's an ugly restriction in the intake tract on '89-and-later Speed Density cars and it's worse for earlier MAF-tube sufferers. The first real performance piece we added was a cold-air induction system from SLP Performance Parts. It eliminates the stock air box and allows cold air to be picked up from the factory hole in the firewall. Installation is straightforward and the kit includes parts to relocate the charcoal canister to the driver side of the engine compartment by the battery.
Aftermarket intake runners are the soup du jour for TPI guys, and SLP makes a set that are actually easier to install than the stock pieces because of the thicker mounting flanges. These things are worked to make power by enlarging the intake tubes and removing the first inch or so of material between the runners where they mate with the plenum, essentially extending the plenum area. More plenum, more torque. The next trick is to cut the plenum divider and the gasket to match, but we decided to keep the first set of mods strictly bolt-on.
Exhaust: No Parts Runs!If you are going to do one thing to your TPI car it should be installing a good set of headers. We've seen 0.60-second gains at the track on a 305 five-speed Z28, and when you see the stock stuff, you'll know why. The cast-iron manifold feeds all the exhaust ports into one centralized tube that takes a 45-degree turn into a small collector. It's like GM hated it. The new SLP tubes slide in from the top pretty easily after you pull all the emissions stuff out of the way. We switched the spark-plug wires to 90-degree-boot style with a generic Summit set and bolted them up. The collectors use a doughnut combined with a variation of the ball-flange design that matches the stock stuff. The sting is the $654.95, but they're already thermo-coated and with a monster-thick primary flange and the trick collector they're not gonna leak.
Beyond that, it's worth the $89 to get the SLP header-installation kit that converts the dual-cat system found on '89-'92 cars into a big single. It makes it so you don't have to go to the parts store, not even once. The two-into-one pipe from the headers joins a 3-inch elbow that connects to the cat. We used a Random Technologies 3-inch catalytic converter that bolted directly to the after-cat via another ball flange but required a weld where the SLP elbow met the Random inlet. Since we also needed to weld up the A.I.R. tube and seal the unused bung on the cat (it's universal), we took the Pontiac to Speedway Muffler in Gardena where Wayne zipped it all up for $35.
The after-cat needs no explanation other than it bolted directly to the factory mounts, has both tips exit on the driver side, and sounds mellow like a refined version of the old Turbo IIs you liked in high school. At full-throttle there is no harsh glasspack rattle.
Second Run: 14.66 at 92.82We were hoping for 0.50 off the first run because that's what a good exhaust system will bag you on these cars. We missed it by a bit and here's why: In the past, we've used a system that basically equates to a straight shot from the back of the cat to a tail pipe using what is referred to as "adjustable" exhaust. It's loud. Also, as we mentioned before, the intake runners will benefit from the plenum porting. Those two restrictions likely cost us a tenth or two. We ran 14.75 at 92.01 mph with crazy wheelspin, then bolted on a set of 26x11.50-16 ET Streets on '91 Z28 wheels, set the timing to 15 degrees, and found a 14.66 at 92.82 in it that corrects to 14.19 at 95.94.
So we're zoomin', and tenths away from a 13-second pass with only a couple of bolt-ons. The other news is that we're bummed that we already spent about $2,500 to get the thing to run right, but that will change when we add a few more parts that will take advantage of the intake and exhaust mods and go fast. Love it? Tell us on CarCraft.com.
'THE COST OF COOL Description PN Source Price Injectors 2017 MSD $480.00 Fuel Pump 12-914 Holley $159.88 Headers 3001C SLP $654.95 Installation Kit 30022 SLP $89.95 Cat Adapter 30038 SLP $34.95 After-Cat Exhaust 31008 SLP $439.95 Intake Runners 20004 SLP $249.95 Cold-Air Induction 21010 SLP $189.95 Used ET Streets and Wheels N/A '91 Z28 ${{{300}}}.00 160 Power Stat 1000 Hypertech $7.39 Fan Switch 60600 JET $38.69 Plug Wires G825 {{{Summit}}} $31.95 Exhaust-Shop Labor $35.00 Total $2,712.61 Previous Total (includes the price of the car) $2,024.76 Big Ugly Total $4,737.37