Machining an Offenhauser Valve Cover --

[goodfellow]

This was one of the first posts on the original GH when it was started back in 2010.

It's not a big deal, but when most people think of a "small milling job" rarely do they realize the amount of time that setup and preparation work requires. This job took almost two hours, and most of it was spent on setup and planning the cuts, -- especially the finish cuts. Nevertheless, it was a fun time in the machine shop this afternoon.

It's an Offy cast aluminum cover for a 67 Chevelle six banger. The original stamped cover has a second opening for the PCV valve, and this one needed to follow suit.

Offenhauser does make nice products and I hated to cut it, but that's what was required.



This is the OEM oil filler and it needed a second opening further down for the PCV valve -- it also needed to be spaced right so that the valve train doesn't interfere with the PCV valve once it's seated in place.





The hardest part was coming up with a clamping setup to hold this thing steady and true.



Once that hurdle was covered, the milling is straight forward -- work from the inside out with a fast speed and slow feed. A bit of Marvel Mystery Oil is a good lubricant and makes for easy cutting.





After "hogging" all the aluminum you can see the mess. I kept a steady stream of compressed air flowing to blow away any chip buildup. Chip buildup can ruin an aluminum finish very quickly.



This is the roughed in pocket  --



Next we mark center and use a hole saw to cut the PCV opening (very slow speed  -- 75 RPM on this geared head mill) and lots of Marvel Oil.





One final pass under the mill for a finish "shave" and this is the end result --