I've searched these forums for a while today and can't seem to find the answer, but are the camshaft timing belt sprockets on this engine simply a tapered-shaft, friction fit to the end of the camshaft itself, or is there a keyway or splines that allows the sprocket to only fit onto the end of the camshaft one way?

If it's a smooth taper-fit, then I presume there must be some kind of marks on the cams and heads under the valve cover that you line up while the crankshaft is locked at TDC?

Got a Bentley CDROM on order but it won't arrive for a couple days and I'm trying to learn as much as I can about this engine to see if I want to tackle the big job this next weekend, or put it off for another week.

 

Yup, taper fit, no keys. The flange (for lack of a better term) sitting just to the outside of the sprockets needs to have the ends with the larger of the two holes pointing directly at each other (there's a Cam Locking Tool available for this purpose) while the crank needs to be locked in to a certain position with a crank locking pin.

 

The cam sprockets are tapered and spin freely on the cams until torqued down. The cams each have diamond-shaped flanges that indicate TDC.

The crankshaft has a TDC arrow mark. Use a 22mm(?) socket and a breaker bar to rotate the crank. You may have to rotate past the mark a full rotation to get TDC.

At TDC, the larger holes in the diamond-shaped flanges will be facing inward on a horizontal plane.

Also, I think there are marks on the cams visible with the valve covers removed.

 

I already learned about the spockets' diamond/flange needs to be lined up with the 4 holes horizontal, and larger 2 of these 4 holes pointing inwards towards each other (with the locking bar across them).

So that means there *must* be some kind of marks on the cams and cylinder heads themselves to line up before torquing down the sprocket to the tapered camshaft ends.

In my case, the sprockets are going to be removed off the cams because I am going to replace the end shaft seals since new seals are included in my parts kit anyway. I was wondering how the camshaft-to-sprocket alignment was going to happen, and that pretty much mandates some kind of index marking system if there's only a smooth taper fit between the camshaft and sprocket.

 

The flanges are keyed.

 

Whew!
That's a relief to know. I was getting worried about micro-degree camshaft timing errors that would be caused by a pure taper shaft/taper socket mounting arrangement if there weren't any precision indexed marks.

Looking at pictures like in this DIY ( link here ) didn't clearly show any such internal precision cam indexing marks, and the prospect of simply painting on some marks to the cam and internal chain prior to disassembly seemed way too imprecise for getting the cam timing correct upon reassembly.


PS: I dig the Corsair in your avatar Shipo. Do you fly? I fly a Van's RV-8 and about to buy an RV-6

 

Back in the era BC (Before Children (and wife)), I flew gliders and an old Cessna 170B tail dragger.

The bad news is I haven't handled a stick or a yolk now for nearly thirty years.