valve guide to valve clearance

Peter Restaino · 2026-06-11T08:56:16-0600

Hello just a couple of questions. I have a shed find 1970 Norton Commando S that Im restoring. The head has iron valve guides. There are no provisions for valve guide seals. No grooves. The clearance for guide to valve stem is around .004 thousands. The valves look servicable. What would happen if I went with this set up or just remove and replace guides with bronze guides and seals. thanks.

Mark Savage · 2026-06-11T09:26:04-0600

Peter Restaino said:
Hello just a couple of questions. I have a shed find 1970 Norton Commando S that Im restoring. The head has iron valve guides. There are no provisions for valve guide seals. No grooves. The clearance for guide to valve stem is around .004 thousands. The valves look servicable. What would happen if I went with this set up or just remove and replace guides with bronze guides and seals. thanks.

Get some from JS motorsport. They work with or without the grooves.

Peter Restaino · 2026-06-11T09:49:06-0600

I like JS stuff, purchased some items and very good quality. I know the clearances are out of spec by about .0025 or so but what do you think may happen or maybe just run good.

Dedubyah · 2026-06-11T12:46:39-0600

I had K Line inserts installed in my guides, saves any problems resulting from removing the guides

valve guide to valve clearance

Peter Restaino

Mark Savage

Peter Restaino

Dedubyah

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