I'm sorry to post this because I know that the topic has been covered, but I just can't figure out what I'm doing wrong. I put my valve train back together and the timing is off. Here's the background: I had a heat problem that caused the head to warp a bit and the head gasket to fail, so I had the head resurfaced and replaced the gasket. I reassembled everything and now it kicks over way too easy (no compression). I put a plastic bag over the muffler and when I turn the engine it's actually sucking air in the muffler, so the timing is drastically off. As I understand it, the timing is determined by only three things, the timing marks on each cam and the flywheel. All of these are lined up properly. I made a picture to clarify how everything is lined up: There are thirteen pins on the timing chain between the 12 o'clock marks on each cam. The spark plug is tight, all the head bolts are tight, and the auto-decompression system seems to be working properly. I feel like I must be missing something really obvious because the timing is so wrong. Please help!