Valve guide dimensions

[Flatplane8]

Hi,

Does anyone happen to know if the AJP8 valve guides are 8mm, 5/16" or something else in terms of bore size? The unworn part of the valve stem measures 7.92mm and a 5/16" guide is 7.94mm. I've got a new colsibro guide from a Norton 850 which is 5/16" which seems to give a good fit, but the engine is largely metric hence my question. the picture shows from left to right, original inlet valve, Norton guide and new inlet valve.

I don't know if the Norton guide will fit, bit its overall length is the same as the ones in the cylinder head at 50mm.

[notaping]

They are 5/16".

I got new guides from powers, but you need to ream them out to 5/16

[Flatplane8]

Thanks! Thats good to know.. Were the powers ones bronze or iron?

[notaping]

Yeah - the new ones were steel. Harder wearing, but also harder to ream. If you go that route, you need a good quality reamer. I was going through a cheap reamer every 2 guides before stumping up for a quality one.

[Flatplane8]

I think I will go bronze, my original ones in the cylinder head are bronze and have generally fared well. I read somewhere on here that someone had problems with the steel guides galling but will need to look that thread up again.

[ukkid35]

https://www.pistonheads.com/gassing/topic.asp?h=0&...