Thread: A little head porting............

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Originally Posted by Hot Rod Nick

Looks good, Ryan.

Take this with a grain of salt since I haven't personally run tests and comparisons, but my impression about porting and polishing is that in most cases it seems to be positive, but there are cases where it can make things worse; ie, reduce power. The fluid velocity at certain points in the head can be adversely effected by porting since larger flow area and same inlet flow results in lower fluid velocity. Scavenging is also effected by fluid velocity. I'll shut up now since I don't know much more than that.

Nick, I hear what you're saying. I've been worried about unshrouding the valves before. So, I just remove material around the valve guide to improve swirl, and I smooth out the casting under the valve seats if there any. I grind enough off the walls to get rid of the casting marks, and blend it all back together and try to leave the original shape of the ports. It's hard to see in the pics. I'm thinking if I do it this way, I won't alter the port flow. (I hope) On the exhaust side I open them up to the size of the gasket and blend it back to the throat of the ports. I really wish this truck could have been dyno'd before we took it apart. Then swapped cams, dyno it again, and then swap heads, and dyno it again. That way you have an idea of what each mod is actually doing. Now, we don't know.