Ok. What I do on the 6 inch strokers with the 400-450 heads is give them a port/polish in the ports. New manifold is a must!! You are flowing more air for sure,,, but not to the point of needing bigger valves. If its under 220 psi cranking pressure, the stock valves will feed it as long as you port the head, Im not saying go all out on the porting,, just a nice clean up to smooth it out. With the port work, new manifold it will do the same as big valves, and then use the carbs' venturi size to match it all up. Ive done that quite a few times and they have amazing low end power. 400 head, ported, cleaned up
450 cam
Vinson manifolds are sold new bout anywhere,,
M carb throttle body, they work better in the long run.
6 cyl carb bowl,, they have a bigger metering stem, and has a larger idle circuit thru the bowl
Good fuel,,,,, Im a beliver in ethanol, so if you can get E85, they run great and make power with E85, mixed with 93 pump gas. How much to mix is relitive to compression pressure,,,, the higher the compression, the more ethanol you can burn. Electronic ign,,,, its just better,,,
lighter springs in the mechanical advance,, picks up throttle responce,,,
stiffer governor spring, speeds up governor responce time, and throttle responce, holds the carb open longer too under a load. Thats the recipe for a real good engine for 6 inch stroke,,,,, My opinion is the big valves are not needed though,,, Hope this helps,,, More info if you need it! Chad
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