Porting the 450

Is there a general technique and/or any tips on polishing / porting your intake and exhaust ports? I see the casting flash and that should probably go.. but the small little divits like on a golf ball are supposed to be there right?

You can make some improvements without the benefit of a flow bench and/or dyno and/or a stack of cylinder heads to screw up while you learn what doesn't work, but you can also create a really beautiful looking set of ports that will run like they were blocked off if you get carried away in the wrong direction.

Here's some general guidelines as to what you can do safely:

> Smooth out any casting flash lines

> Round over any sharp edges. This will help air flow around them. The exception is the counterbored area around the valve guides. It's best not to modify that without some more specific direction.

> Try not to alter the overall size or shape of the port any more than you absolutely have to. Again, mistakes here can produce the wrong result. Particularly touchy are the edges of the webs that separate the three intake ports where they diverge from the main port into 3 individual ports.

> Don't polish the ports to a high luster. A smooth sanded finish is actually more desirable in most cases, as it encourages a healthy boundary layer of air along the port wall.

To do more, you really do need to at least consult with a tuner who has been successful in working with the particular head you have, and closely study what he has done, and why.

Thanks gray

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