By Cam Benty
Regulars of Power & Performance News will recognize a bright red 1971 Pontiac Formula 400 Firebird that has served as the platform for a variety of tech articles. Frankly, I have loved second gen Firebirds for many years, ever since I owned a Lucerne Blue 1970 Trans Am back in the ’90s. Shortly after I procured this Formula Firebird, I began formulating plans for its conversion to a “modern” muscle car.
Over the years, the ‘Bird has exchanged its classic muscle car parts for modern components. Out went the Ram Air III engine in favor of a Chevrolet Performance 525-hp LS3. In the rear, a Heidts IRS suspension replaced the GM 10-bolt, and up front, a full Heidts subframe with rack and pinion steering was swapped for the factory Pontiac pieces.
Not long ago, I received a call from Pat Staton over at YearOne telling me about their new 17-inch Snowflake-style wheels. From my first review of the new wheel online, I knew I had to have this very cool wheel. My only initial concern was whether they would clear the massive Wilwood rotors. Happily, they worked out perfectly.
So, the next hurdle became tires. At the last SEMA show, I had a chance to review the new Cooper Zeon RS3-S tires. Not only was the tire tread very aggressive in style, it turns out the “sipes” in the tire (those little slits in the outer tread of the tire that are rarely discussed) actually have a job — handling!
Cooper spent a lot of time engineering these new performance tires to deliver impressive handling numbers during their testing. Knowing autocross was a major focus for the car when complete, it made sense to go with this tire, and a set of 275/40R17 Zeons were ordered up and installed around the YearOne Snowflakes.
So, here’s where things became challenging. Offset is always an issue to consider when sizing wheels. The Snowflakes have a 5 ¼-inch back spacing spec. When we installed the tires, they were clearly not pushing the tire out to the fenderwell lip. To shore things up, a one-inch spacer was used — not my favorite fix, but the best one on hand.
Next came the wheel well spacing. Pontiacs have big fender wells, especially when compared to their Camaro brothers. The distance between the top of the tire and the bottom of the fenderwell was about 5 inches — off-road truck territory. The good news was the Heidts suspension uses coil over shocks. The bad news was the springs were already as low as they could go, netting a call to QA1’s tech folks.
After talking with QA1’s Damien Brase, I found out Heidts uses 10-inch springs on their coil overs with a 350- to 550-lbs./inch rating. I personally like softer springs for autocrossing/cruising, so I opted for a shorter spring with a softer rate.
QA1 has a vast array of springs and offered up a couple of choices in an 8-inch tall spring, one in chrome (like the original Heidts spring) and one painted. After trial and error, I settled on a 350-lb./inch painted spring. It offered the best tire height to fender well spacing (about 1 inch on final review) and a great ride.
The lowering of the car to set the tire/fender ratio caused me one more issue — the death of my custom exhaust. The Heidt’s IRS does not give much of room for exhaust routing, especially when using 3-inch tubing. Initially, I ran it on either side of the rear end away from the swing arms.
Now that the car is effectively three inches lower due to the spring change, my exhaust is now too low to the ground. My choices were few: either a set of NASCAR-style flattened tubes from Spintech or reroute the exhaust out in front of the rear tires. I have opted for the latter, just to avoid future tubing conflicts.
Cause and Effect, Push Pull, Fix and Modify – I love this stuff!