Valve guide "mods"?

[PhilM]

I’ve just started to clean up my cylinder block prior to refurbishing and rebuilding the engine and I’ve just noticed that all of the valve guides seem to have been cut down, one or two rather crudely and not too straight. Can anybody tell me if this was likely to have been for any specific purpose?



Although I need to replace all of the valves the new ones are a nice fit in these “modified” guides, I’m now wondering if I need to replace the guides in case this alteration has a detrimental effect.

Any advice or observations will be gratefully received.

Many thanks,   ….. Phil.

[Alan]

Probably at some stage to get enough clearance for a high lift cam. If you are fitting new guides it’s best to check there will be enough clearance if you are using anything but a standard cam. If the valve stems fit ok, I wouldn’t worry.

[john williams]

Phil, I was told by a 750 club champion in the early 60s, to tap the valve guide down flush with the port to improve gas flow. And then check that the valve collett collar didn't foul the botoom of the valve guide when vale was on full lift. High lift camshaft might be affected, but I always tap the guides down and have never had a problem. John

[PhilM]

Many thanks for your replies, both would seem to confirm that this is not uncommon.
I don't know much of the history of my engine but I'd assumed the cam fitted is standard, how would I tell?

I've now measured the difference between the length of the existing guides and the new replacement, the fitted ones appear to be 3/16" shorter than the new replacement. The guides have been driven down flush with the casting as john suggests so that alone may explain the shortening.

Thanks again,     Phil.