HRG-Derrington Heads


The firm of VW Derrington was founded in 1919 by Vic Derrington, for the purpose of tuning and racing motorcycles. They branched out into all sorts of automotive tuning, performance and appearance paraphernalia, among which was the alloy crossflow cylinder head made for the BMC 'B' series engines. This moved the intake ports to the right side of the engine, with a separate port for each cylinder, while sensibly leaving the exhaust with the stock 3 port arrangement.

This was called the "HRG Derrington" head as a result of their long association with HRG, who I believe cast up the various specialty bits sold by Derringtons, including manifolds and heads, and because it was originally designed by one S.R. Proctor of HRG. See the link below for more information on Mr. Proctor's involvement in this story.

By the late 1960s, they had sold over 1000 heads and had progressed from the Mk 1, a small combustion chamber small valve version originally used on such things as MG Magnette to the final iteration of the concept, the Mk 4 head. A road test in the May 1962 Practical Motorist of a 1955 Magnette with Mk 1 HRG head and twin Webers showed a 27 mile per hour increase in top speed, although the fitment of an overdrive to the transmission no doubt accounted for some of that.

They stopped production in the 1970s due to increased production costs, according to correspondence I had with Stuart Derrington, son of the founder, who would now be about 54 years old.

The Mk 1 head was a small chamber head with the smaller original valves suitable as a replacement for 1489 and 1588 cc engines. The Mk 2 head was designed with the larger valves first used in the 1622 MG engine and continued on with minor changes through the Mk 3. Both are suitable for MGB application. The Mk 4 was a final development, although a 'Mk V' was sometimes referenced as a competition variant of the late heads.

Various carb set-ups were offered, starting with a manifold to use the original 1 1/2" SUs, although for higher outputs they recommended 1 3/4" SUs. They also offered manifolds for 40DCOE and 45DCOE Webers, some of them for special applications like the TVR shown on this page, which had special short manifolds that cleared the foot box, with 'TVR' cast into them. Although Vic was never able to convince the BMC management that they should offer these heads as an officially catalogued option, TVR did offer them as such and indeed used them on the 1622 engines on their Le Mans entrants in 1962.

Views of the head and some of the variations in manifolding produced by Derringtons can be seen HERE

Brown and Gammons had instigated a new run of heads patterned after the HRG (I don't know if they acquired the rights), and another similar head, the MSX brand is sold by Moss Motors. As the new ones are not legal with many vintage racing organisations,  interest (and values) of the old heads has risen considerably in recent years. I have reproduced both period information releases by Derringtons and fitting instructions for the heads in a PDF file accessible below.

I have raced with these heads in both my TVR and MGA race cars   I ask that you note that the requirements of an alloy head are different than a cast iron part. Do NOT use the hard, thin head washers that Special Tuning sold for the cast iron heads - you will dish them and create depressions in the head. Do NOT over-torque the heads. DO torque them cold, not hot, after you have run them up to normal operating temperature and let them cool down again.

I am compiling a list of numbers from the heads - if you have one or see one, please e-mail me the number that is usually punched on the horizontal flat at the back of the head - the format will normally be xxx/yyy, sometimes followed by a space and then '22'. Later heads may just have a 4 digit number.

I am tabulating data on production number and dates as I receive them. This data may be viewed HERE

I have prepared a file that includes original information from Derringtons, as well as fitting instructions for the heads. Information can be hard to come by, and I thought this might interest and help owners of the heads to use and conserve the remaining units still in existence. The file is accessible below and can be printed out for your files.

Click filename below to access file


The file above with either open as a new page, or download to your computer, depending on how your software is configured. Either way, you will need Adobe Reader to view it.

A couple of comments on the content - this was taken from contemporary copies of factory literature and the amendments may have been made by the factory, or more likely the outlet that had this paperwork. Note the torque settings (lower than cast iron heads). The early valve guides had grooves machined in them with round section rings snapped into place to prevent the guides moving into the head. This was replaced in later production with a specially machined guide with a flange on it, as was done on the MGA Twincam, and that is what the amendment seen in the material refers to. Do not forget to use a suitable shim under the valve spring (the stock washer usually fits, but make sure it bears on the guide ring or flange to ensure that the guide can't move in an upward direction either).


Additional Information:

I use a late HRG head on my TVR race car (that I recently sold)   HERE

I have a section from the book "HRG, The Sportsman's Ideal" by Ian Dussek (ISBN 0 947981 0 04 7 1st publication 1985 by Ian Dussek and Motor Racing Publications Ltd.) HERE  It offers information about the creation of the HRG head following the end of production of the HRG automobile.