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Bored&Stroked · 01-19-2020, 08:05 PM

I'm not a big fan of the split guides - due to the larger opportunity for movement/slop in the guide bore and around the stem - as well as side-to-side misalignment on the stems, etc.. I used to run custom 5/16 valves in my race flatheads (with split guides) - and they well Hell on the stems.

But, if one is looking for optimal port flow, one could just sleeve the late 49-53 guides for 5/16 or 8mm stems - such that you can run valves with smaller stems. Of course you'd probably also have other "features" on your custom valves - to provide less restriction in the port and deliver better flow (especially at low lift).

But that whole discussion heads down the path of high-end race modifications . . . which we could ponder until the cows come home! LOL

01-19-2020, 08:05 PM	#5
Bored&Stroked Senior Member Join Date: Jan 2011 Location: Central Ohio Posts: 5,073	Re: valve question I'm not a big fan of the split guides - due to the larger opportunity for movement/slop in the guide bore and around the stem - as well as side-to-side misalignment on the stems, etc.. I used to run custom 5/16 valves in my race flatheads (with split guides) - and they well Hell on the stems. But, if one is looking for optimal port flow, one could just sleeve the late 49-53 guides for 5/16 or 8mm stems - such that you can run valves with smaller stems. Of course you'd probably also have other "features" on your custom valves - to provide less restriction in the port and deliver better flow (especially at low lift). But that whole discussion heads down the path of high-end race modifications . . . which we could ponder until the cows come home! LOL