In Parts I and II of this story, we learned that the SLP bolt-ons (airbox, headers, hi-flow cat, after-cat exhaust, and 1.8:1 rockers) were worth over 35 hp and 15.8 lb-ft of torque at the wheels, but we wanted to see if our GT could e.t. as quickly as a stock GTP. Unfortunately, I couldn't get the Grand Prix from my busy wife for bone-stock baseline e.t.'s. At different tracks and on SLP's Customer Appreciation Day, we noticed stone-stock, naturally aspirated 3800's usually turn high 15s to low 16s at 82-84 mph. We'll have to use those observed e.t.'s for our baseline. With the SLP mods, we were hoping to go high 14s or low 15's-that's stock supercharged 3800 territory.
Another mod for testing is the new SLP Ram Air H.O. hood (nicknamed Cyclops). This new fiberglass hood will not only save some weight, but it will also allow the engine to ingest cooler outside air and will provide a meaner appearance.
Before installation, technicians at Charlie's Auto Collision (Little Egg Harbor, New Jersey) block-sanded and painted the SLP hood. I later found out I should have followed SLP's instruction sheet and trial-fitted the hood before installation (see captions).
At The Track - Our co-workers from GM High-Tech Performance and Muscle Mustangs & Fast Fords magazines arranged a test day at Raceway Park, English-town, New Jersey. Most racers know that E-Town is one of America's leading tracks when it comes to traction and low e.t.'s. For our strip test, we were greeted with a wonderful Indian summer day for October with a high of 72 degrees.
When we began testing, the temperature was a cool 68 degrees, and the crew at E-Town sprayed the track surface with the sticky stuff to ensure a good bite. We inflated the tires to 35 psi front and 45 psi rear. Our heavy toolbox was removed from the trunk before any passes were made.
After a one-hour cooldown from the 90-minute ride, we pulled our Poncho up to the line. By slowly stepping on the go pedal to avoid wheelspin, we were rewarded with a 15.12 at 89.72 mph. We hot lapped (minute-later-backup run) for more starting line practice and turned a 15.19 at 89.34 mph.
For the entire day, we cooled down the 3800 by utilizing the SLP fan switch. All runs would be made with the stock gauge just rising from the 160-degree mark for when we pulled up to the line. Consistent driving and temperature control would be the best we could do for reliable strip test results.
Next we removed the solid, holeless lid from the top of the SLP airbox and installed the ram-air lid with the hole to let the cooler and denser outside air in via the hoodscoop. At this point, it was 70 degrees. A quicker 15.06 at 90.26 mph was the result. Impressed from the gains the fresh-air hood provided, we were now aiming for the 14s.
In our quest for a lower e.t.s, we removed the screen from the MAF sensor/throttle body. Right away we noticed better throttle response, but would we be rewarded with a quicker quarter-mile? The mod helped us to a best-of-the-day 2.16 60-foot along with a slightly improved 15.05 at 90.00 mph. We tried a minute later backup run, but slight wheelspin slowed us to a 2.24 60-foot and 15.15 e.t.
We weren't about to give up on the 14s, but like a real knucklehead, I forgot to bring SLP's Air Temperature Module. The module could have added a couple more degrees of spark timing to help reduce e.t.'s further, just what we were after.
This left us to try one of the oldest tricks in the dragstrip book-reduce weight. Right away we went into the trunk and removed the spare tire and jack. This brought our race weight down to 3,480 pounds from the previous 3,530 pounds. We crossed our fingers and pulled up to the line. After the holeshot, the scoreboard lit up a 2.18 60-foot with some light tire hazing. Looking at the lights as we crossed the stripe, we observed the magical 14. Yes, you can believe we were stoked! Halfway back on the return road, we read the whole score-a 14.98 at 90.65 mph.
Conclusion
We were pleased to run 14s by adding SLP's bolt-ons and Performance Distributors' ignition parts to a naturally aspirated V-6. I remember bone-stock GTOs and T/As running similar e.t.'s back in the '70s. Today's technology enabled us to get yesteryear's V-8 performance and four-cylinder-like gas mileage. We now have an inexpensive (less than $10,000 with bolt-ons) four-door sedan that can run with or beat the new and more expensive (less than $30,000) sedans.
Fuel Mileage Results
180-mile test loop, three passengers, 70 degrees, A/C on
