Originally Posted by old1951
Thanks for your input. I value your experience immensely. I agree with you. I'd expect the cam lobes to point away from the valve and have the lobe heels approximately centered on the lash caps. But when my cams have the end grooves parallel with the piston travel (like the manual states when using the BMW cam alignment tool) the #1 intake cam lobes appear to be 90 degrees from this position (thats what bothers me).
In thinking about it, I cannot remember exactly where the lobes were at TDC, I just remember that I positioned them that way checking the valves. In thinking it through, at BDC the intake valve should have just closed, within a few degrees, so would move about 90 degrees away from that when the piston is at TDC, putting the flat surface that just left the cam follower about 90 degrees to the follower face. I am sitting here trying to remember which way the engine is turning, but forgot.
The part that bothers me most about this whole thing is that it should not matter what position the engines in when you take it apart as long as the crank is not moved and the cam gears/cams are re-installed in the same orientation as the were removed in. My cam gears were both positioned with the tear drop shaped holes in the gears facing up and divided by the head/valve cover split line (as seen in the shop manual diagrams). This puts the cam gear slots in the cams and gear pins facing the crankshaft (again this agrees with the shop manual). When the cams are in this position the opposite end slots are parallel with the piston travel line ( again this agrees with the use of the BMW cam holding fixture). Since the gears were ty-wrapped to the chain and the crank never moved, I can't imagine how I could have it 90 degrees out? If the cam chain slipped on the crank a tooth I could understand having it of one tooth out, but not 90 degrees.
You are correct, if the crank did not turn, the chain was ty-wrapped to the sprockets, and you lined up the slots on the back of the cams and got the sprockets back on over the timing pins without pushing the pins in, then there is no way it could be misaligned now. Just to be sure, pull the cam sprocket bolts and washers so you can see the timing pin holes in the sprockets to be sure they are on the pins correctly. Again, if you are at TDC, and the cam slots are perpindicular to the head, there is really nothing to worry about. Forget the lobe positions, as long as both valves are closed and the slots are correct, the timing is correct.
At this point I totally frustrated and have begun to doubt my years of engine building experience. It's very frustration not having easy access to the crank gear. In a V-8 I'd throw a degree wheel on the crank and degree in the cam.
But here, I can't do that. Maybe I'm over thinking this issue, but a bent valve can prove to be fatal.
Clarify something for me, your saying the cam grooves in the cam ends opposite the cam gears are suppose to be vertical (parallel with the valve cover/head splitline? The BMW shop manual say they are supposed to be horizontal (in line with piston travel)?? This is how the BMW cam holding tool holds them. Maybe this is where I'm screwed up?
I said the grooves in the back of the cams should be perpindicular to the head surface, not parallel. You are thinking correctly, I think you just misread my statement.
Maybe I should throw the manual away and go back to my Engines 101 experience. Just get #1 at TDC and position the intake and exhaust lobes so the lobe heels are centered over the valve cap and in line with the valves.
No, as I said above, the intake valve should have moved about 90 degrees past the valve closing at TDC, the exhaust valve should be roughly 90 degrees away from starting to open the exhaust valve, at near BDC.
I think your settings are probably correct. At TDC on #1, the valves should both be closed, and the slots in the back of the cams perpindicular to the head surface. It they are, then you are right.
Sorry to vent! I'm not vent on you, its just my frustration over something that aint that complex, but has me questioning weather the sun will rise in the east.
Believe me, I have been there more than once, having questioned myself until nothing seems right any more, then after calming down and thinking it through realize I was mis-analyzing to the point I could not see the forest for the trees any longer. Walk away and think of other things for awhile, come back and start looking at fresh, and the doubt goes away.
Again, thanks in advance for the answers to some of the above questions and for taking your time reply.
Hope you find that you were correct all along, and just like I did a couple times just got caught up in a temporary thinking error leading you down a rapidly dissolving mental state.
Shake your head a few times to clear the cobwebs, go back and walk it through again thinking of what is going on in the engine as it rotates around, I think you will find you are just fine.