Left: Exhaust bowl after porting but before being cut for bigger valve. You can see where I smoothed the guide boss and the transition to the port itself.
Right: Intake bowl after basic porting but before enlargement for 1.94 valve. Again you can see the reshaped valve guide boss and the smothed transition to the port.
Right: You can see the intake and exhaust ports from the outside. It's pretty obvious that the intake port passage wasn't even touched where the exhaust was reworked pretty extensively. My theory was that the exhaust on these heads is weaker than the intake side. I wanted some gains in high lift on the intake side but primarily desired the exhaust to be more along the lines of what the aluminum castings from FRPP provide. Mostly I just cleaned up all the sharp edges and smoothed the transitions from the passages into the bowl and the chamber.
Text and photos by Guy Tate
This is my first attempt to modify any cylinder heads. I was pretty hesitant until I found these heads for $150 shipped so I didn't feel so attached that I didn't want to experiment with them. They are brand new bare castings that have never been installed or assembled.
My goal was to create a set of heads that flowed well for cheap. I wanted heads that would justify the time and money that I spent on them (I'll cover the costs in detail later). I used the FRPP "Y" heads for my personal comparison. To accomplish this I felt that I had to open up the exhaust port and do decent bowl work on both the intake and exhaust. Initially, my work was very conservative since I had read that it's easy to mess up the "P" heads and actually lose CFMs throughout the entire lift range.
I did almost no work on the intake port side since it was already the size of a 1250 Felpro gasket. I had a set of 1262s here and thought about opening the intake up to that size but I've heard that this will kill the lowend torque of the "P" heads and might also lower the intake velocity.
I wasn't as careful around the valve seats as I could have been but the plan is to install REV stainless 1.94 and 1.6 valves which will require regrinding the seats anyway. I also plan to have them milled about .030 to raise the compression a bit.