Is it easy to pull a guide out of my old engine then or are they pressed in at manufacture?

Just something that if it's reasonably easy to do then i'd do it just in case.

Hmm but still a guide that was bent enough to 'slow' a valve moving through it would be quite apparent wouldn't it? They seem ok to me upon inspection so i'm going to change a couple of springs anyway as those, if they're weak, would surely cause the same effect at speed.

Like I said though i'll build it up tomorrow with old bolts etc, time it up and manually turn the pulley wheel, take the head back off and see if there are any imprints in the stuff i'll stick on the crowns. Yup i know this'll only emulate slow rotation but it'll eliminate what someone else mentioned before about the cam possibly being wrongly positioned on it's pulley.

Nighty night peeps, catch you tomorrow!