Rebuilding a basket case 250 Chev. Fired up in stand, sounds like a rod knock. So I tear it down, rods about .004 to .006, journals all look good just worn down to the copper. So I tighten the bearings up to .002 to .003, figure it's good. Fire it up, SAME NOISE. Bang-bang-bang one per crank rev. Pull the fuel pump & belts, same noise.
Pull all the rods, piston pins all tight, all looks good. Soin the crank all quiet. Spins easy. Add the cam & spin it over with spinner wrench: THERE IT IS. Either the cam gear or retainer plate or crank-cam gear mesh is making the noise, once per crank revolution. Aluminum cam gear, steel crank gear, looks all factory.
Anybody ever hear a noise like that? What is it?
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