Prepare the Camshaft Assembly

I had a few minutes to spare, so I decided it was time to put the camshaft gear onto the camshaft. The alignment procedure is: with the timing mark on the cam gear pointed up, the lobe farthest away should point down. (The timing mark is a little dot at the base of a tooth just past the 12:00 position.)

Drive on a camshaft from a Porsche 914 engine


Because I'm going to run an oil pump that's a little larger than stock, the bolt holes in the cam gear need to be recessed a little bit. This, in conjunction with the heads of the bolts being machined down a little bit, should provide adequate clearance between the bolt heads and the oil pump. I used a little thread locker on the bolts, too:

Close-up of blue loctite on a bolt for the Porsche 914 camshaft assembly


Place the cam in the engine and put the oil pump in place. The oil pump is a gear displacement pump - as the two meshing gears turn, oil is trapped in the space between the teeth and the outside wall. In this picture, the cam rotates counter-clockwise and the oil pump gear on the left has a shaft with a flat tab that goes into the slot on the end of the camshaft. The hole that is visible on the side of the pump is the pickup or suction side - the oil goes into the pump here (it can't get through the center of the pump, because of tight tolerances where the two gear mesh there is no room for the oil to get through), is transported in the space between the gear teeth along the perimeter of the pump, and to the other side where it gets pushed (now under pressure) to the oil filter:

Relationship of oil pump and camshaft in a Porsche 914 engine


And, good news, the heads of the bolts do clear the pump:

Camshaft bolt head clearance in a Porsche 914 engine


But, bad news... the other side of the bolts don't clear the case!

Camshaft bolt interference in a Porsche 914 engine


A little careful grinding is needed to "shorten" the bolts and then some good deburring with a wire wheel to make sure there are no little metal shards that will eventually fall off and make their way though the engine.

Grinding down bolts on a camshaft from a Porsche 914 engine


Success! The bolts are now short enough for the camshaft to spin in the engine case:

Camshaft bolt clearance in a Porsche 914 engine

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All pictures and text copyright 2008