Been ages since I did anything on this! Been too busy getting our Bonneville race bike ready!
I'm a bit stuck for options in the UK, and splashing out on some very expensive CNC heads would just about bankrupt me I think! So as I had these stock heads here I thought I would make use of them. Not my first porting job by a long stretch, but it is the first set of LS heads I've done.
5 hours in and I've got one head roughed out with the carbide cutter. Just need to finish it off with cartridge rolls and give the exhaust ports a polish.
After they have been skimmed I'll polish the chambers and unshroud the valves as well.
I had a scrap head here as well, so decided to drill the ports in a few places to find out how thick the walls were as I wanted to remove quite a bit of material, especially around the exhaust ports.
Started off by marking out the inlet ports on the face so they were all the same size.
And here's a stock inlet port/valve throat, there's a big step where the cast runner meets the seat insert which you might not be able to see in the photos.
First thing I did was dive in with a big carbide cutter and blend the seat into the throat
Then in with a smaller ball cutter and worked on the area around the guide. I did think about cutting the guide back, but I can't see any huge benefits from doing so?
I didn't really touch the rest of the port apart from cleaning up a few casting marks. I just need to run a cartridge roll all the way through the port to finish it off
Inlet ports all squared up and equally sized
Next the exhaust ports - these were even worse where the seat meets the cast runner - but the port was a long way behind the seat insert, so all I could really do was clean it up a bit and blend it as best possible.
The main work on the exhaust side was at the port exit. They seem very small at the manifold, so I marked them out and then cut quite a lot of material out of the ports including on the top and bottom of the runners so as to make the port the same size all the way through.
Here's a side by side comparison
And all done
Not sure if what I've done will actually result in any gains... but it passes the time!