Cutting guides for dual springs - diameter?

[modnrod]

What diameter does everyone cut their guide supports for when preparing to use dual valve springs?
After the guide posts have been trimmed, is it still possible to replace the guides, or will this inevitably result in cracks and breaking the heads?

I want to try out some beehive springs as part of my next big science experiment, but they have an I.D. at the bottom of 19mm (I think 0.755"), so I would need the posts down to 17-18mm, which makes them thin.
Do you think it would make them TOO thin?

[K-Roc]

Hi The "Standard"  ( if you want to call it that)  is  .625"  however in my opinion that is much thinner than needed for most dual springs, or in your case the Beehive.. I cut the bosses just thin enough for the inner spring to clear,   .755' will be no problem.

It is possible to re-re guides without splitting thin bosses, you have to core drill your guides and also top them flush with the aluminum boss before trying to drive them out.

Cheers

[modnrod]

Thanks man.
I almost pulled the pin on a guide cutter and pilot for the Chev Vector heads, but they have the usual .625" I.D. and I thought that was too thin as well so haven't got the tool.
If the spring I.D. is .755", then shouldn't I leave .020" clearance for spring harmonics (eg. guide post O.D. .715"-".700") so I don't get alloy paste in the oil, or will it sort itself out with it's own clearances on running in and be fine after that you rekn?
Spring is Comp 26113, heaps big enough for my build.