I am helping a chum with replacing the cam/dynamo/distributor gears on his A7. In dealing with the cam gear we have found that the cam will move a good 5mm fore and aft - which feels like an awful lot! I cannot find anything in Doug Woodrow's manual about how to adjust if necessary. If this movement is excessive might it account for the fact that three gears (cam, dynamo,dizzy) had teeth worn razor sharp - but the crankshaft gear is almost unworn? Might this movement also account for an OK tickover but uneven running at speed?

All advice gratefully received. Nick

Nick,
5mm is definitely not right, it should only be a few thou, barely descernable in fact. With that much float the valve timing will change due to the skew of the gears and it must come close to getting contact between various moving parts, it could be making the engine rough.

Is the nut tight? Is the cam floating that much or is the bronze bush behind the gear moving as well? It's retained by the screw above it, square headed as standard to stop undoing but often replaced by a normal hex head. Its supposed to have a round peg on the bottom that locates the bush but the 'kick' from the gears often opens it up usually accompanied by a good oil leak. I've never seen that much though! I think there's been other correspondance here on this subject but my prefered solution is to rotate the bush, redrill the oilway and put in the groove then drill and tap down through the thread in the crankcase so a hex head screw goes into both the crankcase and bush. A bit of Loctite helps as well.

Dave

Thanks Dave. I don't think the bush is not moving at all and the retaining bolt is correct, and tight. I can see an engine-out job on the horizon...

Sorry - wrong glasses. Bush is NOT moving.

Nick,
Something at the back of my memory thinks that the really early engines didn't have the flange on the camshaft? What type of engine is it? Any early engine experts out there? Don't pull the engine out yet!
Dave

Dave - Not sure of year as I don't have crankcase number to hand but it is a manual advance/retard with dynamo so I would think '33-35'ish??

I suspect that a less than brilliant engine rebuild has taken place in the recent past...

If the bush is not moving, how is the cam able to pull in and out? It feels as if it is not fixed properly at the back end of the engine.

Nick,
The camshaft is only located at the front end. There's a flange that runs on the back of the bronze bush and the gear has to be fitted to the shaft taper to give a running few thou clearance onto the front of the bush. Is the gear on straight? The only way I imagine I could deliberately build in that much float is if the key is not in the keyway. Try taking the nut off (it should have a cup oil thrower and tabwasher) and look up the keyway?
Dave

I was really careful with the key and am sure it is in place correctly. Might the bush have broken up from the inside face, leaving the outer face still intact (for now!)