The recommended fuel pressure...
The recommended fuel pressure for Edelbrock carbs is 5 psi. We hooked up a fuel-pressure gauge and found 7 1/2 psi, which can cause flooding under hard braking or cornering and raise the fuel level in the carb. A fuel-pressure regulator could have set our minds at ease, but for now we note the discrepancy and move on.
Carb tuning can be done on the track, testing on a deserted open road, or, most appropriately, on a chassis dyno. We decided to take the beastly Barracuda to Westech for a spin on the chassis dyno and a tune to the carb. The only problem was that the little fish was garaged a good 200 miles from our favorite test facility, and we just stabbed in an 8 3/4-inch rear sporting 4.10 gears. The sensible decision would have been to trailer it, but that would have meant giving up the chance for a marathon shakedown run. We were drawn to the open road, unsure if the decision was adventurous, a disaster waiting to happen, or outright foolish. Leaving the tool kit behind and armed only with a cell phone and AAA card, we had the old Plymouth gassed up and on the highway at dawn. The lack of a heater core in the dead of winter was annoying, but more troublesome were the open windows in the icy air to ferry out the noxious fumes emitted through the tailpipe-omitted exhaust system. Three hours and three tanks of fuel later, we rolled the flat-black bomb into Westech, a little weary from the drive and the effects of a gut-full of carbon monoxide. The 318 fared better, buzzing for hours on end at around 4,000 rpm, quite an endurance test for a 35-year-old factory-built mill.
We drove the Barracuda to...
We drove the Barracuda to Westech, where they were shocked to see the condition of the machine we prized so highly. Suffering some indignation over the ragged looking 318, the flat black primer, and pool of oil escaping the crankcase, we dared Westech's John Beachtel to blow it up on the dyno. He donned his Elvis safety glasses and set out on a disconcerting rampage of abuse. Does this man look like he cares about our 318's survival?
It seemed the ratty condition of our prized ride was an open invitation for abuse. Overworked from the high rpm jaunt, our trusty little 318's rear main seal was seeping oil on Westech's spotless floors, drawing jeers and comparisons to the Exxon Valdez. As the Barracuda was dutifully strapped to the SuperFlow chassis dyno, the air was filled with the sound of haggling and wagering over how many runs the engine would survive. Justifiably proud of the 318's endurance, we defended its honor and laid down the challenge, despite that it was our only transportation home. "Blow up? Go ahead and try. You're not dealing with a small-block Chevy here," John Baechtel heartlessly brutalized the 318, maniacally winding it well into valve float on its fragile and fatigued stock valvesprings. Ha! Nary a protest from the reliable old 318, except for the momentary lifter clatter at the end of the runs as the tappets regained their equilibrium. Tough, those 318s.
The baseline pulls showed an absurdly rich mixture, falling within the low 10:1 range on the dyno's readout. Leaning out in steps following the Edelbrock chart, we first went 4 percent lean on the primary and secondary. This was still not enough, so we followed the charts until we had dropped the fuel flow 12 percent, or three steps lean. The instru-mented fuel ratio read more appropriately in the mid-12s. Power wasn't up radically, but we didn't expect it to be. In fact, the 318 was making pretty good output, with nearly 200 hp showing at the wheels. That's 5.0 Mustang territory, and this was a high-mileage grandma mill, far past retirement age. It always did feel pretty spry.
We found the jetting significantly...
We found the jetting significantly rich. A few turns inside the big Edelbrock got the fuel flow under control, curbing the black smoke and producing a few more ponies. Despite having a well-worn, high-mileage stock 318 under the hood, we were awfully close to 200 rwhp with our simple tune-up.
The tune had one dramatic effect, and that was a significant increase in economy. We didn't tally the CAFE statistics, but we only had to make two stops on the 200-mile journey back in. What did all this prove? Once the tuning basics of the Edelbrock carb are understood, mastering the metering is no mysterious matter. Four hundred miles in this ragged roller was enough to gain some new respect for the venerable 318, although we've got to do something about that exhaust. Now, if you'll excuse us, we're headed for the oxygen tent.
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