Thanks again for the interest, hopefully this little project has been helpful to see what can be done to increase the performance of the old SOHC head with minimal work and to this point zero cost. The reason for this thread was to show what could be done at home and on a budget. I would say that a solid 8 CFM (10%) increase in flow with our intake port is worth noting. Pretty much from this point on, gains are going to be smaller and more work intensive along with adding costs.
Again so far I am happy with the results, we now have a head for very little cost that is now capable of supporting 10 horsepower more over a stock casting, the added benefits would also be that with the additional flow the useable rpm range of the engine has been increased and raised.
It has been suggested to replace the guide and perform more work, and naturaly these would be some of the next steps to take. The aftermarket guide would offer a smaller overall diameter and size, along with the abilitly to use smaller stem valves if desired, both would produce additional flow. With this project I am nearing the end as to work for increased flow, this head has a date with about 15-20 pounds of boost so working for every last CFM and running the budget up is not really needed.
I am however curious to possibly try out a set of aftermarket stainless valves that have a reshaped head and under cut stem, these would most likely be the next step to take for addition flow and keeping on a budget. I am sure they will be lighter as well allowing for a little more additional RPM before valve float. I will shop around for a set.
I am also working on testing just the stock intake "spigot" by itself to see just what its limits might be, I have a feeling that we are getting within a few CFM of its ability. Also I will be working on the exhaust side and showing some before and after shots.
