250's manifolds install the same way. I install both manifolds loose to each other and loose to the head. Starting in the center working out towards the ends, I tighten the top bolts so the manifolds are pulled up. 250's have the row of bolts staggered some high some low. If the low ones are tightened first, you can not pull the top tight enough to sell the top edges of either manifold. Once both are tight to the block, I tighten the two manifolds to each other.
Get them as close as you can and tighten the two together. Then remove the whole assembly from the engine and check for flatness with a straight edge or flat steel plate. If they need a little sanding, use some sticky back sand paper on a flat panel and sand the whole manifold at one time. Cast iron cuts really easy and it won't take very much to help them seal.
Joe
Last edited by Joe H; 10/19/2012 5:27 PM.
