Chevy Camaro Headers, Gears & Posi Upgrade - My Generation Camaro, Part III

Third-generation Camaros make wonderful budget builders, because you can buy them dirt-cheap. If you've just joined our performance buildup, this is the third part of a multi-part performance construction project where we started with a basic carbureted LG-4 305ci small-block with a TH700-R4 and a lazy 2.73 rear gear. The best part is that our pal Tim Moore bought this jewel for a paltry $271. Up to this point, we've added an intake manifold, a dual-snorkel air cleaner, a stronger mechanical fuel pump, and an after-cat exhaust. The Camaro responded with minor e.t. and speed improvements, but what it really needed was headers and a gear.

It's tough to make power if the air and fuel gets in but can't get out. Last month, we added an intake manifold and air cleaner, enhanced with a larger after-cat Flowmaster exhaust system. Unfortunately, our little 305ci engine was still trying to exhale through stock iron exhaust manifolds, a 2--inch Y-pipe, and the stock replacement catalytic converter. The first order of business was a set of headers. We searched through several header kits and settled on Edelbrock's 1-5/8-inch headers for the early third-gen Camaros.

The headers are completely smog-legal since they retain the original air injection reaction (A.I.R.) fittings to inject fresh air into the exhaust to help reduce hydrocarbon (HC) emissions. Car-owner Tim Moore reported that he had to move the steering column to fit the driver-side header in place. The passenger-side pipes also required some finesse to install.

The final part of the job involved some modification to the Y-pipe. We ordered the headers for a standard 305 Camaro, not the High Output (H.O.). The H.O. systems use a larger 3-inch catalytic converter, which dictates using a 3-inch Y-pipe from the headers to the catalytic converter. Since we ordered the smaller header system before we realized that we needed a 3-inch catalytic converter, Tim decided to modify the existing Y-pipe to increase it to the 3-inch size. The easier thing to do would probably be to order the H.O. headers and exhaust, and the whole system would bolt together.

We also needed a larger catalytic converter to help this engine breathe. These early systems used a single catalytic converter, so a larger 3-inch converter is essential for better breathing. DynoMax offers several universal high-performance catalytic converters, and we selected the 3-inch inlet and outlet converter. Once the converter was in place, the entire header and new converter conversion operation required the better part of eight hours to complete. Since Tim was able to do the work himself, we didn't have to pay for labor, but you could expect to pay over $400 for a muffler shop to perform this task.

Before we moved on to the gears and Posi, we decided to test the Camaro at Los Angeles County Raceway (LACR) to evaluate the performance improvement. We were expecting around a half-second improvement and hoped we might see more. LACR offers a Wednesday night test night, so we bopped up to the high desert. Even though this was an evening excursion, the air was still plenty thin with a density altitude of 4,400 feet (see "Altitude Adjustment" for more information on density altitude). At first, the Camaro was hesitant to deliver, but with a cooler engine and a higher shift rpm of 6,300 rpm, the Camaro responded with a corrected 16.29/86.59-mph pass that was a 0.46-second and 2.3-mph improvement over the previous test.

These were encouraging improvements, even if we still were only running low 16s. But still, the Camaro was going through the lights in Second gear, and we knew that what we really needed was a deeper rear gear. It was time to get serious.

Roughly a month before, we had been touring our local Pick Your Part self-service recycling yard and ran across a 2.8L V-6-powered Blazer with the standard 7.5-inch, 10-bolt rearend. Tim knew that many of these tiny V-6-powered SUVs came with a deeper 3.73 gear to give them some help from the stoplight. Someone had already relieved the dead Blazer of its spider gears, which made removing the ring-and-pinion a snap. The gears were on an open carrier, so we unbolted the ring gear and managed to walk out with an excellent set of 3.73 gears for a paltry $22.50.

A couple of days later, Tim found a Posi unit in a third-generation Camaro for a mere $25, so for less than $50, we had gears and a Posi-traction unit. We then ordered the deluxe Ratech rebuild kit through Summit for $120, which offered all the bearings and parts we needed to install the new gears. While we could have cheaped out on the bearings, we figured this would give us a virtually brand-new rear axle that could probably take most of the abuse we could dish out. Again, Tim installed the gears himself so we didn't have to add any labor to our running bill. However, you can expect to pay around $100 to $200 to have a professional shop install the gears.

With new lube in the rear axle, it was once more time to hit the track. Tim again drove the Camaro back up to LACR. Now the Camaro was much more responsive and much more fun to drive. Usually, a 3.73 gear is a pain to drive on the freeway because the rest of the world is cruising at 75 mph and you're stuck at 60 or 65 mph. But with the TH700-R4 overdrive, the effective rear-axle ratio in overdrive computes out to 2.83:1, which is extremely comfortable to drive. With our 26-inch tall rear tires, the cruise rpm was a paltry 2,560 rpm at 70 mph.

The best news was what happened at the track. The one full point of additional gear ratio made a big difference. The 305 still doesn't have the torque to fry the tires, but this means it doesn't spin the tires hard enough yet to require an investment in sticky tires. After a little tuning with secondary metering rods (we found an AY secondary metering rod worked the best), the Camaro cranked out a corrected 15.82/86.74 which was a stout 0.47-second improvement over the previous combination. The mph picked up only slightly, but we were also facing a very stiff wind that night that got so bad it knocked our last run down by 7 mph! The Camaro would probably be 1 to 2 mph faster in better conditions than the speeds we've reported here.

Combined with the headers, gears, and Posi, the Camaro is now a full 1.6 seconds quicker and 8 mph faster than it was a mere two months ago. Not only that, but the Camaro also has a street presence now with its more authoritative exhaust note, and enough gear to take maximum advantage of the remaining modifications. In an upcoming story, we're going to bolt on an emissions-legal Crane hydraulic roller cam and a set of World Products S/R Torquer heads that should put some power to the ground. Our goal is to run in the high 14s. That's a lofty goal considering that we'll need to pick up over 0.80 second just to run a 14.99. We're not sure the 170,000-mile short-block and rings can seal the cylinder pressure needed to do that, but it should be interesting to find out.

Our '87 Camaro is shaping up nicely as a real-world performance car. It's already fun to drive, still gets over 20 mpg on the freeway, and is slowly becoming quicker every day. We can't wait until next time.