Valve guides

[Greenfield]

I'm fitting new cast iron valve guides to my B40. The first one was cooled in the freezer first, to shrink it and it broke 3/4 in. The second I fitted at room temp and went in no probs. I've now ordered a replacement to complete the job. Has anyone got experience of whether they should be cooled or not before fitting?

[AWJDThumper]

It's best to heat up the head first and then press them in rather than using a hammer and drift. Cooling the valves first won't doing any harm and may help.

[sidewaysid]

I can only say one thing, I rebuilt at least 50 Triumph twin motors, and a few BSA A10s, I replaced all the valve guides, so lets say 200 guides, some bronze and some cast iron, I never broke a one, only old ones coming out, which were damaged. I swear by using a gas blow torch all around the guide area, having the head firmly secured in a vice or something, get it really hot, so hot that if a drop of water was poured onto it, the water would bounce and dance around, then carefully line up the guide, and with the special tool, firmly knock it into place. never failed me. Hope it helps you out.

[Greenfield]

Thanks for that. I heated the head first plus cooled the guide in the fridge and it went in fine. I've fitted a dozen or so guides in the past, mainly cars and never had a problem before. I wonder whether it may have been a defective guide. Anyway job done.

[sidewaysid]

Hi
Strangely enough I put new guides into my B31 head today, and was thinking about you ah ah ah