Squish Bands Milled on '11 XL1200 Heads

[aswracing]

If you just took a stock XB head, at 62cc, and cut a 15 degree squish band sized for a 1250, it would add about 2cc is all, bringing it up to 64cc.

We have the option of doing a second relief cut to get it up to 67cc or so, where it needs to be for a Thunderstorm type piston.

But more often than not, the heads are also getting other work at the same time, that includes a competition valve job. This tends to make the chamber larger, too.

So what ends up happening is we do all the work on the head, including seat work and porting, then cut the squish band, measure the chamber, and then deck & recut the squish band as needed to get it down to the target chamber size.

[aswracing]

By the way, in case you're curious about how we do the chamber cuts, we use this program:

This is something we developed in-house, just to help automate things. Basically, you put in all the parameters of the cuts you want to do, hit "GENERATE CNC CODE" down there at the bottom, and the program goes off and writes the CNC program (in what's called G-Codes, a really primitive programming language) and then downloads the program to the machine. We then hit the start button on the machine ...

... and it goes and performs all the operations. Very automated, repeatable, and accurate.

[Dolfo 109]

I am doing my math on compression and the 1212 piston with 15 degree dome should be ca 8cc dome volume. Right ?

[aswracing]

Yes, that's right.