NH350 camshaft locking up on assembly.

[dennis.t]

I am rebuilding a 1956 NH350 engine from used parts. I bought a camshaft and inner timing cover from an earlier model (no dowel holes). The camshaft locks up when I tighten the case screws unless I use a vey thick homemade gasket. Is that acceptable or is there an underlying problem?
The gasket is made from good quality gasket paper. I tried thinner paper but only the thickest paper I have stops the camshaft locking up and gives some detectable end float on the shaft.
The inner timing case looks to be original, albeit from an earlier model, with no signs of having been modified.
I don't know much about the camshaft other than it is a single lobe type described by the seller as a "high performance cam".
Dennis

[will_curry]

I don't remember ever having issues with no endfloat on a cam but I have had
issues with the bushes not aligning when swapping timing chests.

I put a vernier across a known good camshaft and got 1.685".

It's possible your performance cam has been built up and not done well.

[dennis.t]

Will,
Thank you for your reply. The camshaft bushes line up and the shaft moves freely so I do not think it is a problem with the camshaft alignment in the bushes. I tried another inner timing case that I have, an unserviceable one, with the same result.
I only mentioned the profile of the cam for information. The cam itself looks fine and looks like a professional job. With my home made gasket everything works as it should. My only concern is why such a thick gasket is needed?
On my VH500 I used the thin paper gasket from a gasket set without any issues.
Dennis

[will_curry]

The need for a thicker gasket suggests a lack of clearance and, if the camshaft isn't too long,
then it suggests that there is an issue with the bushes being effectively too close.

This may be because one or both have moved in their housings or that one or both housings
have been damaged. Given that the problem happens with two different cases I'd inspect
the crankcase bush quite carefully first.

Given that there are clearance issues I think I'd make sure that there was sufficient endfloat
on the cam followers and not too much either with the thicker gasket in place.

[dennis.t]

Will, good point about the crankcase bush. If it is the camshaft length there is not much I can do about that since I have no access to a lathe. The thick gasket provide a small amount of end float for the shaft sufficient to give free rotation of the shaft so I will go with that for now.
Dennis

[Simon.Gardiner]

I've had this problem after fitting new camshaft bushes and pushing one fractionally too far in.
I'd ease one bush out a tad (you only need a couple of thou probably) - it could just be the inner radius on the shaft (or a bush) that's binding slightly.
All that matters is that the cam lobe or the camwheel doesn't bind on any aluminium, which should be easy enough to check.

SG

[dennis.t]

Simon, thanks I'll take a look.
Dennis