Splitting The Rockers
One of the things we did on the “Memento Mori” ironhead was to split the rockers. This isn’t a new thing, but the Ironhead rocker covers are different from Shovel rocker covers. They are shaped differently, with one side coming to a square corner and the other having a curved corner. They also have fewer bolts, so if you eliminate the middle bolt you only have three bolts holding each rocker half, not four like a shovel.
The way we modified these came from Weyland at Solutions Machining. He nailed it, modifying Ironhead rockers really requires getting the two sides symmetrical for it to look right. In fact, the brass nuts we used on the ends of the rocker shafts are a product he sells and they are awesome.
We snapped a bunch of pictures along the way, so let’s get started.
Layout and Cutting
Take a look at the shape of the rockers and you’ll see what I mean about them being asymmetrical. If you just split them it will accentuate the difference between the two sides.
I started by using a contour gage to copy the curved profile. You could do this with cardboard of course.
Then use your pattern to lay out a matching cut line on the squared-off side.
Point of No Return
There is no turning back now. First cut from the face of the rocker straight back maybe 3/16". This is to keep us from cutting into the area where the shaft goes. Then cut off the corner using the guide line.
This should be (more or less) what you end up with. Hey Joe, isn’t this likely to leak now?
Go ahead and cut the other head the same way. Then cut the “bridge” between the two halves out, and you’ll end up with something like this.
Lay out some guild lines with a sharpie and contour the two inside (middle) faces. We’re just rough grinding to get the shape close at this point. I used a grinder with a no-load disc made for aluminum. Use the flat of the disc and make even passes.
You should have something that looks like this now.
The reason we wanted to rough in the center ares is this: There is (was) an oil passageway through the bridge we cut out. Counter sink (bevel) the hole and TIG welding it with 4340.
Now let’s do something about the big hole. We need to cut a little piece of 1/4" 6061 aluminum plate to fill the hole. Hold a bit of paper over the hole and rub a dirty finger over the paper – presto! Instant pattern.
Now go ahead and weld it up. What you want to do is weld up the hole in the corner and then do a nice penetrating weld around the patch. Note that I have a used rocker shaft in place to help control distortion. I welded beads edge-to-edge across the face to build up material for shaping.
From here it is just grinding, then sanding, to get the contours even across all four cover halves. Grind one, make a pattern and grind the others to the pattern. A sandpaper roll on a die grinder helps get into the inside corners, and my 3" D/A is rarely out of reach – it’s an swessome tool for detailing small areas.
It’s not a great picture, but here is a shot of the modified rockers, chromed and installed on the engine during re-assembly.