Timing chain question

Ok so i faced my fears (unfounded it seems) and rebuilt the engine which last night included re-installing the cams and cam chain.
I followed the manual counting the 28 pins from right to left and all looked perfect. Installed the top tension assy and then did one full rotation of the crank to check nothing binds (as in manual)
the manual then says the marks should line up again with the cogs but obviously after one rotation the mark i made is somewhere down below as one rotation is not enough to bring it back round.
So i continue to rotate until the mark shows and by then it's nowhere near #28 on the left cog.
Am i being thick or is the manual talking a load of bollx? I would have thought it would have done exactly that and not stayed in line after a few rotations.

I think everybody has been bit by this one. It takes two full crankshaft rotations to get the cams around one full rotation. It you set to the correct cam align marks and turn the crank one rev, the cams will be 180 out from the initial "correct" set point. First time I did it I unbolted the cams and reset them since clearly they were "wrong"...... later I realized what happened.

If your alignment actually shifted, the only way is if the cam chain is jumping links on the drive gear on the shaft. Very bad, only happen if the chain tension is too slack.

bountyhunter wrote: I think everybody has been bit by this one. It takes two full crankshaft rotations to get the cams around one full rotation. It you set to the correct cam align marks and turn the crank one rev, the cams will be 180 out from the initial "correct" set point. First time I did it I unbolted the cams and reset them since clearly they were "wrong"...... later I realized what happened.

If your alignment actually shifted, the only way is if the cam chain is jumping links on the drive gear on the shaft. Very bad, only happen if the chain tension is too slack.

I'm sure i thought of that but it's all a bit of a blur now.
i put the valve cover back on last night but i think i'll take it off again and just check the cams line up..