Rebirth of OHC-6
Short answer: Before swapping out a repairable OHC-6, try fixing it — the common running problems are a vacuum leak at the hard-to-reach carb stud (a steel base gasket cures it) and a gummed-up distributor vacuum advance. Swapping in a V8 means motor mounts, a trans cooler, a bigger radiator, engine-harness rewiring, and cooling baffles — a lot of work to replace a historic engine.
About the engine: the OHC-6’s belt is reliable — it’s the oiling system that wipes out camshafts (top-end oil starvation). It came as a 1-bbl base (9.5:1) and a 4-bbl “Sprint” (10.5:1, dual valve springs, the first production Quadrajet, high-lift cam, dual exhaust manifolds, 215–230 hp). It was 230 cid in 1966–67 and 250 cid in 1968–69; 1968 blocks are the best to build.
The automatic is a Super Turbine 300 (closer to a TH350 than a Powerglide), in air-cooled (OHC-6) and water-cooled (V8) versions. The manual uses a 3.10:1-first transmission and a longer z-bar. Speed parts are available from Clifford (cams, headers, Weber kits); usable power is ~3000–4500 RPM even though it revs to 6500–7000.
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Content last modified: June 13, 2026 at 10:06 am
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