W-72 upgrade
I owned a 1978 TA with that engine combo: I put true duals(2.5 pipes with turbo mufflers) and opened the hood scoop. I then recurved the distributor with an over the counter weight kit, used the middle (gold) springs and brass limiter bushing(got an approximate 22 degree curve at the crank), which worked out to 11 degrees in the distributor and moved the timing around to where the engine liked it (generally 12-16 degrees initial running premium gas), all centrifical timing in by 3000 rpm (at the crank). Ign total timing ran between 34 to 36 degrees, remember these heads were an open chamber design and if I had used 39-42 degrees I would have caved the pistons in- That would have ruined my day. Used all new Accel ignition components as well as a hipo coil. Then richened up the carburator primary jets 2-3/000ths, did NOT change primary metering rods, used a set of pontiac over the counter secondary metering rods-I believe 031 short tip ram air 4 variety- allowing for headers in the future. Also, ground off 1/8th of an inch off the top of the accelerator pump rod so it will sit higher and give you a richer pump shot when you nail it. The 79 w-72 cam, part#10003402 only has .374 lift on the intake side vice the more normal .406 lift which reduces the breathing at midrange and top end so you need to use 1.65 rockers on the intakes to balance out the breathing. installed poly locks and ran the engine, backed off each till it clattered loudly, turned it in till noise went away, then turned it down another 1/4 of a turn and tightened the adjustment, this allowed me 6000rpm when I needed it and kept the engine stable under load at lower speeds. installed 160 degree thermostat, carter hipo mechical fuel pump and Hurst linkage. Car had 3:42 gears so I did't screw with those, rear was posi. Performance improved significantly, could easily light tires up in first, bark second and third. Also installed 65-68 full windage tray and ram air oil pump, H.D. pump driveshaft and was able to cobble 79 L-82 chev clutch fan hub(noticeably looser-alot of milling/ drilling on that one to make it fit). Oh, one final item, No air conditioning and manual windows-who ever ordered this TA wanted a machine-the car was quick from jump street-I just tweeked it!!
|