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The last time I had my 454's heads off I decided to install new valve guides, cut the guides for PC seals, larger 2.19"/1.88" high performance valves, port match, and pocket port them. As I have my own World War II vintage Black & Decker valve and seat grinding equipment the pocket porting and seat grinding didn't cost me anything other than my time. If I recall the new guides set me back $65, the PC seals $30, and the larger Manley Pro Street stainless steel valves $125 so they weren't all that expensive.

The heads on my 454" are 1966/1967 396"/427" closed chamber large oval port heads that came on the low performance 396" and 427" engines. By port matching, pocket porting, and installing larger valves they come close to duplicating the flow of the rectangular port heads at lower rpm's but with much better street manners.

I port matched them to Fel-Pro #1212 Print-O-Seal gaskets that had identical openings to my Air Gap intake manifold which were about 3/16" larger (all the way around) than the head's ports so I removed a lot of material. However the biggest gain was by pocket porting which increased the diameters under the seats by about 1/2". That alone added an additional 500 rpm of breathing.

For all of the material removal I used a 6" extended nose pneumatic 1/4" die grinder (not shown) and several shapes of carbide burrs. The extended nose die grinders are inexpensive through E-Bay at around $30 and the carbide burrs at around $5 to $7 each
 

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