Ford created a virtual stroker version of the 200 with the development of the 250. Although not a bolt-in replacement, to use the "stroked 200" - 250 is not complicated.
The 250 was developed from the earlier 144/170/200 family of engines.
In order to accommodate the large increase in stroke from 3.126" to 3.91", the block deck height was increased and the cam location raised. Outwardly the engines appear very similar, but measuring the deck height (crank centerline to top of deck) shows that the 200 has a 7.808" deck height and the 250 has a 9.469" deck height. The cam is repositioned higher in the block to provide for crank clearance...
The 250 because of the longer stroke doesn't have the same RPM capability of the 200 as far as extreme revving. The limitations of Log breathing/Wedge head makes it logical to use the killer torque capability of the 250 at more reasonable RPM's.
Clifford Performance built Ford 250 six engine- Jahns 10:1 Pistons, Clifford rods, balanced bottom end, Fisher balancer, 1.88 int. valves, Ported and relieved, Offy 3X1, Re-curved distrib., the works...
I reckon you can nearly squeak a 221 crank into a 200 block. You will have to relieve the cam even more, and possibly look at smaller big ends. But it's not a huge amount of extra clearance for 10% more cubes in a fairly small block.
.....YOU WILL HAVE TO RELEAVE THE BLOCK AT THE OIL PAN. THE 221 HAS EACH ROD AREA ON THE INSIDE RELEAVED WITH ABOUT A 1/2'' BEVEL. THE OIL PAN GASKET IS SAME BUT THE BLOCK IS ABOUT HALF SIZE BETWEEN THE MAINS.
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