• Welcome to the website of the Vincent H.R.D. Owners Club.

    Should you have any questions relating to the Vincent H.R.D. Owners Club, or Vincent H.R.D. motorcycles in general, please contact Graham Smith, Hon. Editor and Webmaster by calling 07977 001 025 or please CLICK HERE.

    You are unrecognised, and therefore, only have VERY restricted access to the many features of this website.

    If you have previously registered to use this forum, you should log in now. CLICK HERE.

    If you have never registered to use this website before, please CLICK HERE.

Iron head valve seats


Well Known and Active Website User
VOC Member
What is the opinion with regard to the best way to restore damaged / pocketed valve seats in cast iron series 'A' heads. Welding or fitting seat inserts? If inserts are fitted, what material should the insert be made from? Has any,one had a bad experience of either method?
Regards Richard.

Marcus Bowden

Well Known and Active Website User
VOC Member
I had an over pickled head as it was given to me by Jim Jennings of the Count House Cundorow Camborne, many years ago as he's been dead since 2003 same age as my mother be sold my brother his first Vincent 1965,
Robin Jeffries who had a workshop next door to Conway's put in steel inserts, lead-free I think about 1996. Was hoping to get it running this year but COVID-19 has I think stopped that happening. Welding cast iron not generally good unless you have a specialist nearby.


Well Known and Active Website User
VOC Member
VOC Forum Moderator
Conways fit separate hardened seats suitable for lead free fuel to their new series A heads.


Well Known and Active Website User
VOC Member
I once had an 'A' head welded by a "specialist". It was a disaster.
As Simon says Conways are the best bet; call them for a chat.
Peter B
Bristol, UK


Well Known and Active Website User
VOC Member
Hi Peter,
The original head on my Comet had inserts. No problem with them ever and as a bonus, the inevitable crack problem was completely fixed. I only changed it for a new one because of all the missing fins.

Ian Savage

Well Known and Active Website User
VOC Member
My A Comet head had inserts when we acquired it, one fell out in Canada at the International, John McD fitted new ones, I think with material used for alloy heads, it fell out in less than an hour. We concluded the iron head crushed the seats which are much smaller in section on the A so when the head cooled the fit was lost.
Had the heads welded by Cast Iron Welding Services, Coalville great job.
Can't remember who remachined them possibly Conways.
No problems since.


Well Known and Active Website User
VOC Member
Not knowing the prewar engines but I´d fit high chrome tool steel inserts, 1.2379 is about the same as you can get from the motor trade with production seat rings, no welding on cast iron for me. I did inserts on the 1935 Guzzi 30 years and 30 000 km ago, all well with unleaded since. Same with the 2 l Ford Capri ohc cast iron head, perfect since 100 000 km at least. In an iron head you need some decent material around the seats for sure , same with alu heads. Plus the rings need wall thickness as well for staying put. After heavy machining the rings to near finish size put them on an electric cooking plate for an hour at max. temps 500 degrees or so for stress relieving and then only finish them for 2 thou press fit , no heat necessary, just bash them in square,a bit of lube is allright.

Guzzi GTV 500kl.jpg