My alloy head VH has a lose exhaust valve guide yet again. When I first bought the bike the guide had been rocking all over the place so the head had to be bored considerably oversize and an oversize guide was made. That repair failed some years later so again the hole was trued and a larger guide was made. The current guide is at .715” dia and may have to go to .725”. the original size is .625”.
The aluminium boss around the guide is minimal toward the centre of the head and I am wondering if this may be the area that fails. I am currently considering having a lot of weld placed around the boss to provide more support, 6 oclock to 2 oclock in the photo. The weld would then be machined down to form a lot larger valve spring seat area.
Does anyone have any other ideas or suggestions.
David
How does the cost of a brand new head compare with the re-machining costs every few years?
Paul Jameson
35 LG (project), 37 RH500, 52 ex ISDT KHA, 54 KH(A), 75 Healey 1000/4.
Former Machine Registrar & Archivist, General Secretary and Single Spares Organiser (over a 25 year period).
Now Archivist (but not Machine Registrar), Gauges and Clocks Spares Organiser.
John
The bike has bronze valve guides and has always been fitted with bronze guides. The alloy VH head is renowned for the exhaust guide coming loose. There is not a lot of length between the valve spring seat and the exhaust port to hold the guide. The total length of support is 12 mm not all of which is fully supported as seen on the left side of the photo.
Strangely enough I ordered a new head from Martyn Adams back in April before my current problem became apparent. Martyn had a batch of heads cast years ago, and went to England to collect them in June but it appears that they are still not finish machined. So I am still waiting.
The heads that Martyn supplies have smaller ports than the original Ariel heads or those supplied by John Budgen. The overly large exhaust port in the original head is some of the reason for the lack of area to hold the guide. That is part of the reason that I chose one of Martyns heads
All of the new heads that are available are sand cast unlike the original 57 head which is die cast so it remains imperative that I have the repair work done from an originality perspective. I also want to never have to do it again.
David
My head is repaired and about to go back on the bike. The repair was done by first welding around the boss to provide more lateral support, then by boring the boss a little larger to true it, and then an aluminium sleeve was pressed in. Finally the sleeve was welded in position around the top and then bored true for a standard guide, and the spring seat refaced. As the valve seat had been cut for a couple of prior repairs it was too deep so a new exhaust seat was also fitted. So the bike will be running again shortly.
David
