Just done a valve shim check on the spare head. Intake are as good as they will be but the exhaust are a little on the small side for gap, which is about 0.02mm at a guess. It's a bit tight on the 0.20 feeler and should be 0.21 - 0.25 (0.008 - 0.010 in). Would this cause an issue? Never done all this before. I won't have more shims to play with until I prize the knackered head off.