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Cam timing oops


Vehicle Information: Model: xxx; Year: 1984; Body Type: Coupe; Engine (type, size, modifications): xxx; Total Mileage: xxx;

Last night I replaced the cam housing O-ring and gasket to try and fix the oil leak on the left side of my engine. Due to a misunderstanding of the geometry of the cam sprocket, I had the left side cam advanced about 15 degrees from where it should be, which equals about 30 degrees of crankshaft rotation. I turned the crank by hand with the tool kit 19mm offset wrench from compression TDC maybe 160 degrees when I felt resistance. I was turning the crank slowly, maybe 15 degrees at a time because the spark plugs where still in the engine, and it was hard to turn. I backed it off, then gave it another tug. Thats when I realized that maybe my valves where touching. I backed off to compression TDC again, then realigned my dowel pin. This time I was only two holes off and it was a little easier turning the crank.Im not even sure if it was a valve that hit the first time, but I wasnt willing to crank hard and press the issue. I think the valve should be strong enough to withstand the pressure I put on it without bending, but the Porsche microfiche has big warnings all over it about not touching the valves to the pistons. Is it possible that I did any serious damage to the engine?As part of the current to-do list for my car, Im going to set the valves clearances tonight while the covers are off. I figure if I did bend a valve it should show up as a high valve clearance. Does this make sense? Being a gearhead at times, it was kind of interesting figuring out how the cam timing worked. There are no explanations in any of the microfiche or Haynes manuals. Turns out there are 16 holes in the cam hub and 17 holes on the cam sprocket. So moving the dowel pin up a hole gets you 1/16-1/17 = 1/272 of a rotation, or 1.32 degree cam rotation, or 2.65 degree crank rotation. In replacing the cam gasket and O-ring, I was hoping to just reassemble everything where it was before. I initially figured that only the sprocket hole on the hub mattered, so I only kept track of that hole, and its location relative to the cam sprocket. This would have worked if there were 17 teeth on the cam sprocket to go with its 17 holes, but there are actually about 28 teeth, so cam sprocket orientation is important as well. This is why I was 15 degrees off when I reassembled everything. If I had marked the cam sprocket hole as well as the hub location, I think I could have thrown everything together the way it was when I disassembled it. Luckily, I found that just by eyeballing the location of the cam, according to the way it was, you can get within a couple holes of the correct sprocket location.

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