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1 When we last visited John Douglas and our 289, we had a stout short-block waiting for some equally promising top-end parts. In the interim, we sent our factory original 4V intake and reproduction Hi-Po manifolds to Extrude Hone for its Abrasive Flow Media process. AFM ported and polished the inside of the manifold passages without having to dissect or cut open the castings, perfect for our "hidden horsepower" theme. Here, John started building our top end by checking piston-to-valve clearance, then he degreed in our Comp Cams roller cam using checking springs on the intake and exhaust valves of the No.1 cylinder.