Bit of progress with the head. Starting with a bare JP4 head, bit grubby at the moment and desperately needing improvement!
First thing I do, is attach a bare manifold flange and machine it into the ports, to get it matched perfectly and make starter marks for the hand porting, which helps with the precision. This is one really handy feature of making our own inlet manifolds, it can be made with the head, to get exactly the tract shape and size I want.
At the valve end, I start shaping and sizing upwards from the inside of the valve seat:
One of the most important things to master with porting, is repeating what you've done accurately across all the cylinders! When you get frustrated by the differing core shift of the casting, you know you're getting it! One of my frustrations with this casting can be seen here, the slight dip in the long side left by the factory throat blending machining. They go deeper than they need to and you need to balance losing it with getting the size and shape you want. Compromises have to be made with most head castings, how you manage them matters to the engine you create.
And having got the basic size and shape of the whole tract done using cutting tools, I tend to leave it for another day, so that I can come back with a fresh and critical eye, before commiting to the smoothing and finishing with abrasives.
