Modifying Engine Tin

Well, after too long a hiatus, I finally got to spend a little bit of time on my engine over the 4th of July weekend. I mocked up one side of the engine (cylinders 1 & 2) - first putting the crank and cam in the case halves, then grinding my cylinder shims a little bit for proper clearance around the head studs:

Cylinder spacer for Porsche 914 engine


After sliding my cylinders in place and setting one of the new heads on top, I was able to put the "engine tin" - the metal shrouding that directs air over the cylinders and head - in place to see how it would fit:

Sheetmetal cooling ductwork on Porsche 914 engine


My new heads have the spark plug locations modified, so I will have to "move" the original spark plug access holes. To mark where the location should be, I was able to put a Sharpie marker in the spark plug hole to mark the tin:

Marking proper sparkplug hole location on Porsche 914 engine "tin"


Here I've marked up both locations (see my little cross hairs?):

Underside of Porsche 914 engine tin showing where new holes will go


After using a center punch, I was able to drill holes with a step-drill (which works great for sheetmetal, by the way). Probably most people would use a hole saw for this step, but I don't have one that size - but do have a knock-out punch that is the right size.

Drilling holes on Porsche 914 engine tin


A knock-out punch is a little die and anvil set with a bolt going through. First you make the holes in your sheetmetal the right size for the bolt (3/4" in this case), then you slide the one piece over the bolt, put the bolt through the hole, and finally, thread the other part onto the bolt. After a little turning, you have a clean, round hole!

Using a knock-out punch to create new holes on Porsche 914 engine tin


Both holes are made in their new locations:

New holes made on Porsche 914 engine tin


And now it's time to weld up the old holes! I used the knockout slugs from the new holes and some random washers I had laying around.

Old holes on Porsche 914 engine tin welded over

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All pictures and text copyright 2008