OHC-6 Buildup

• Cam/bearings: the cam rides directly on the aluminum housing — there are no replaceable cam bearings, and the housing rarely wears even past 200,000 miles. Wiped cams come from oil starvation, so make sure the head’s oil restrictor is intact.
• Valves: do NOT tip the valves (you’ll get interference between the follower and spring retainer; lash adjusters compensate for stem height). Valve stem height is critical — have it measured, not eyeballed.
• Compression: keep CR just under 10:1 for the street; 11:1+ really wakes it up. A killer combo is a 1966–67 4-bbl head on a 1968–69 short block.
• Valve springs: if running singles, match the Sprint dual-spring specs; with a 1-bbl head and valves you’re near coil bind on a 4-bbl cam.

Valve stem lengths (machinists often grind these by eye — don’t):

66 1-bbl  4.9     67 1-bbl  4.9     67 4-bbl  4.99
68 1-bbl  4.8     68 4-bbl  4.9
69 1-bbl  4.8     69 4-bbl  4.9

Dual exhaust (Sprint splitter look): the factory used a Y-pipe off the dual-outlet manifold. A good DIY route: buy over-the-counter V8 dual exhaust — the crossover muffler, front resonators, and V8 tailpipes (the dual splitters) — but not the V8 front pipes; install it with proper hangers, then have a muffler shop custom-bend the two front pipes (max 1-7/8″ dia) up to the resonators. Or copy the factory axle-tube pattern in 2–2-1/4″ pipe.