Tuesday, 12 April 2011

Alan Coultas 4 Valve Velocette

This was a significant machine owned and developed by Alan Coultas of Hull, and with which he achieved considerable success at National level over many years. Alan was one of the “Yokshire Velocette Mafia”, who truly built this machine in the back of a garage at his house. He was also handicapped by the fact that he did not ride himself and relied on feedback from a string of riders of differing abilities.
Alan Coultas mark 1 Velocette 4 Valve cylinder head
The first version 4 valve Velocette engine made by Alan was fabricated from a stock venom head and used a clever ‘hinge’ arrangement to operate the pairs of valves via the standard rockers and cover. The second version was altogether more sophisticated and used a purpose made casting, the patterns being produced and pouring taking place once again in Alan’s garage. The design incorporated many clever features such as a cast-in skull and separate exhaust port for each valve. It proved reliable and immediately gave a useful increase in power throughout the rev range.

The Alan Coultas mark 2 4 valve Velocette cylinder head
Its Achilles’ heel however was the rockers and after several unsuccessful attempts to cure the problem, the project was sadly mothballed in favour of a much modified 2 valve Velocette part. This engine he further developed over time and in its final form used a fully squished twin plug head with piston to suit. It was a very fast machine indeed and in the capable hands of Tony Myers, almost lapped the entire field at Cadwell Park to win the E.A.Lavington Trophy. He was not invited back!
The Alan Coultas 4 Valve Velocette


  1. While the mk1 head could pass as Velocette, the mk2 is clearly the business, if crude. I note that his Seeley chassis uses an AMC gearbox; curious why he ditched the Velo item and associated clutch?

  2. Alan did not like Velo gearboxes/clutches. Velo clutches can be a bit marginal, but to me a well developed Velo clutch/gearbox is a great setup. Alan used a different drive-side mainshaft - I think from a G50 if I remember correctly.