Camshaft/Valve clearance questions

[fool73]

I am in the middle of taking my camshafts off to re-adjust the valve clearances (looks like I didn't quite get a couple right when I rebuilt my engine).
My first question is, is it OK to take both camshafts off at the same time ? The manual says to do one, then put it back, then do the other, but I want to measure all the shims up at the same time so I can buy any replacements I need together before refitting.

Secondly, I am puzzled by part numbers 149787 and 149788 (pin cam sprocket, and nut) The nut obviously goes on this pin, but is the nut supposed to be tight up against the cam sprocket ? One of mine is loose (moves by finger) and if so, how do you tighten it ? It seems that the pin would just spin in the hole in the sprocket if you tried to tighten it.

[Peter]

No reason you cannot disconnect and remove both cams - if you replace the timing chains you need to disconnect both but you don't want to be turning the engine with one sprocket on the bracket so I would remove the lock tabs putting the bolts back in finger tight then line everything up and remove. Not sure about the nut 149788 but if you mean the large thin one not in the parts catalogue apparently holding 149787 to the sprocket - On my engine the nut doesn't tighten on a thread on the pin they were just bonded in place with some resin, once the engine is assembled there is no need for the nut as the pin is retained by the cam and sprocket. My guess is they were assembled for convenience at the factory but aren't strictly needed when you are doing one engine.

Hope this helps

Peter

[flying farmer]

The nut is just a press fit on the pin, no thread involved, and is to hold it all together during assembly. The idea is to put a non nylock not on the pin and tighten it to hold the bracket firmly before undoing the cam sprocket retaining bolts. Usually not a problem provided the nut is a loose fit on the thread.

The theory is that the engine can then be turned to reach the bottom bolt which is difficult to get at.

Once one cam is removed it should be possible to turn the engine to do the other cam. Don't try it with the cam still fitted as the valves will hit the pistons.

It has not happened to me (yet), but it is sometimes possible for the timing chain tensioner to click up one notch meaning the tensioner will need resetting. Forcing the sprocket back on to the cam with a too tight chain can cause jackshaft problems.

Provided the sprocket pin is firmly held to the bracket you should be ok.

Neil

[fool73]

Thanks for the replies. I have gone ahead and removed both camshafts at the same time. Both have guide line lined up with the mark on the cam bearing cap so should both go back on OK.
I am still confused about this hex nut which is on the pin that goes through the cam sprocket. If it has no thread on it, what is to stop it coming off and dropping down into the engine ?
I must be being a bit thick (again) but it's not making sense at the moment.