1978 Trans Am & 1973 Formula 400 - Birds For All Reasons
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In comparison to the W72, the code-YS, '73 L78 400 pumped out 230 hp. Though a Q-jet still mixed air and fuel, the cast-iron intake didn't feature the restricted secondaries of the '78. It has a points-type distributor instead of HEI, and the cam is an 066 with 273/282-degrees duration and 0.410/0.415 lift. Compression ratio is 8:1 for the '78 and the '73. The same style log manifolds carry spent gases from 4X heads with the same valve sizes, but the rest of the exhaust system is different. The '73 employs twin pipes that feed into a crossflow muffler behind the rear axle and end in twin tips; the '78 system (in stock form) has a y-pipe into a single cat converter, and then splits from the converter back into two pipes with twin resonators and tailpipes with splitters. View Related Article
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