Originally Posted by
champ20B
Man, your hungry for knowledge! Well, here is a few good words for start. I have souped up some motors in my time (10-30+hp ). Now here are a few basic things to keep in mind....porting is pretty simple as long as you don't deviate into uncharted territory. What I mean, is by starting without changing the port height (timing). FYI, you don't want anything over 160-170 degrees if you want it not to be too peaky and need chambers. You want about 140-155 psi compression for a hot rod job. Ignition timing might need to be readjusted by feel after then.
Anyway, if your ports are rounded, then just note how tall they are and wide. Keeping these dimensions the same, make the round holes square. For your intake ports, do the same just equal to the area of the carburator venturie +5 or 10%. The intake port posts can be given a sharp knife edge in their centers on the trans passage side (I call it funneling). Polish and round any edges into the transfer passage for good flow. Get some boysen double reed valves. Get some slightly bigger carberators. Extend your exuast port covers farther from the exhaust ports for more free flow without added noise, with a spacer. You will just need to take a gasket for a pattern to a local machine shop and have them cut you a spacer as thick as you want. Its an old trick of mine.
Remember, that if you ever want to raise ports height, never take off material on the bottom edge. Only take off from the top edge toward the head. Sometimes you can cut out a port post or two as long as the piston rings don't pop out. Another good idea is to get an old worn out racing powerhead that someone raced as modified, pretty cheap. You can measure it out all through and use its dimensions as a learning guide to do to a motor you want to build. Other than that, there is so much one can do, you could write a book 2 inches thick about it! Have a good one!