During the summer, we spent a lot of time at the California Department of Transportation (Caltrans) shopping for used work trucks. The first two we bought were nicknamed Jake and Elwood and served as an experiment for Car Craft and Chevy High Performance to see if they would respond to upgrades and function as reliable and inexpensive parts-chasers. We soon found that we could pick up 20 or 30 percent more power with basic bolt-ons. We also found that they look darn good with a decent paint job and they tend to start every day. So we bought a third. Once we saw the "Cone Zone" sticker on the bumper, its nickname suddenly seemed obvious. We'd like to introduce Cone Head. Join us as we help it earn some respect.
AdoptionMost municipalities are going to have a fleet of beaters to fix potholes and haul copiers to the courthouse, and that usually means there will be an auction to pawn off the older models. Cone Head was number four on the Caltrans auction list in Sacramento that included primarily '93 models and some '94s. We wanted the newest truck we could get for the cash, but we were outgunned on all the '94s and ended up with a '93 GMC Sierra in Government Orange with a TBI 305, a 4L60-E overdrive transmission, and air conditioning. We had checked Cone Head out earlier in the day and found no rust and a reasonably straight body. A couple of dents were OK, but we knew that fixing the engine is always cheaper than hiring a good body man, and we were willing to gamble that the drivetrain was serviced by the state on a regular basis. We bid knowing there was no guarantee that the engine wouldn't explode on the way out of the parking lot, but at least Coney would look good behind a tow truck.
Checking The BaselineThe big plan for Cone Head was to put a little heat in the engine with some basic parts and a tune-up, then maybe move it up one more notch with a cam and street-legal heads later on. Yes, we wanted a daily driver and parts-runner, but deep down we want a little snort under the black and blue pedicure to fend off the jackal bearing down on us in his espresso-injected Beemer.
All of that comes later. First we needed a baseline to build on. We rigged Cone Head for testing with a backpressure gauge that we plumbed into the exhaust using a welded bung and installed our Innovate Engineering air/fuel meter that we can't seem to live without these days. Brother Jake had a cat full of particles that had increased the exhaust backpressure about 11 psi, so we were pleased to find our pipes producing only 6. A quick inspection revealed that Cone Head had been treated to a new cat courtesy of Caltrans not too far in the past.
The first run on the dyno netted 122 hp and 181 lb-ft of torque. Doing the quick air-math, we figured that the quarter-mile e.t. on this truck would be around 20 seconds; no surprise there-it's stock. The O2 reading was 11.9:1-12.0:1, which was actually slightly rich compared to the average smog-legal California vehicle's 13:1 ideal, but overall everything looked good with lots of room for improvements.
Stepping It UpStill glowing from the freebie cat, we visited Muffler Time so our pal Rick Stout could bolt up some Flowmaster duals. The Caltrans cat was welded in place, forcing us to chop-saw the flange off of our pristine kit and weld the two ends together, making it no longer a bolt-on. We were still ahead of the game when you consider a good cat is $400.
We also wanted to add a chip from JET to maximize the fuel and timing curves and still be legal. The performance kit from JET also included underdrive pulleys and a throttle-body spacer. After a thorough scrubbing under the hood, we added the JET parts and performed a simple tune-up, tossing in some GMPP chrome valve covers to make it look like we'd been under there.