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From memory either Sid Lawrence or a chap in Melbourne, whose name escapes me at present both developed a squish head Venom in the early 1960s.
I am unsure if it was as a result of speaking to each other or they came upon the idea independently.
Basically the engine was a pushrod version of a late1950s/early 1960s Manx Norton in combustion chamber shape and piston profile.
The Manx Norton squish idea was developed by the Polish engineer, Leo Kusmicki, who initially worked at Norton as a cleaner I believe immediately following WW2 in which he was a Spitfire pilot in the Polish Airforce, but came to the attention of Joe Craig who utilised him in the race shop and many believe used his ideas as his own. Certainly Kusmicki rarely featured in the press and seems unknown to many people, including Norton enthusiasts.
Eric Hinton knew him from the time the Hintons were involved with Norton racing in UK and Europe and Eric told me Leo was the brains behind Nortons racing success once the squish engines were developed.
The squish head used by Norton and the three Velocettes in Australia, all had machined deep lands in the hemispherical combustion chamber. See the photograph of the Velo head, taken by me at CSIRO, Division of Animal Physiology, Prospect, NSW in 1964.
The piston has opposite lands on it and goes into the cylinder head to almost make contact with the head at these lands.
The most effective gap between piston and cylinder head over these lands is around 0.035”.
The so called squish clearance.
Too little and in operation the piston will hit the head, too little and the squish effect becomes lost.
After we photographed the squish Velocette head, we sent a photograph with a letter to Bertie Goodman, then Sales Director of Veloce Ltd.
Years later he replied that they had used this idea in a batch of 12 special engines built for the Velocette Venom Thruxton.
In fact the L.J. Stevens sponsored Thruxton that won the 500cc class of the Production TT in the IOM in 1967 used one. The head resulted in an additional 4½ bhp from the engine.
My involvement was with the late Keith Smith.
Keith ordered a new Velocette Venom Clubman Veeline( called a Mk.1 version now) in late 1963 from the then Velocette agent in NSW, Hazell & Moore Pty. Ltd.
Few Velocettes were sold in NSW from around 1960 when the then State Government made what to motorcyclists were draconian alterations to the compulsory Third Party Insurance on motor vehicle registrations. Bikes over 250cc were particularly disadvantaged with large premium increases.
I can’t remember the figures now, but 350cc machines and most 500cc machines disappeared overnight. Few were imported. Victoria and other States were different and Frank Mussett Motorcycles in Melbourne, Victoria continued to sell Velocettes ok.
Keith took delivery of his new Clubman in the packing crate as it was sent from Veloce Ltd in early 1964.
I was at his house when they arrived from the docks and we excitedly opened the crate. To reduce the freight volume, the wheels had been removed and bolted to the inside of the crate near the top. Somebody in the packing section at Veloce had nailed the lid on and the nail went offset and into the tyre, so we had a puncture before we even started!
Then..Hazell & Moore were really reluctant to accept the problem and only wanted to patch the tube!! After we just bought a new motorcycle off them…
Keith rode the bike on the road briefly before he decided he would convert it into a road racer.
He was very friendly with Sid Lawrence, who I mentioned earlier had developed a squish cylinder head. Sid was extremely secretive over it and I recall if he had to remove the cylinder head from the bike in the pits at a race meeting he had a large canvas cover that he spread over the bike, crawled under it and worked there in the semi dark and heat in the Australian summer so prying eyes didn’t get a look….
Somehow Sid revealed the details to Keith who machined the head to Sid’s dimensions, we fitted valves into the head and poured bees wax into the combustion chamber to make a mould of it. Then took the mould to Sid Willis, ex successful Velocette racer from the 1950s who was “Mr piston” in NSW and Sid cast a special piston to utilise.
We fitted the head and left the next weekend on a shakedown ride to northern NSW, myself on my 1958 MSS.
The bike was plagued with overheating problems, pinged etc. In desperation at Armidale we found an old chap with a workshop and fabricated a thick copper head gasket and limped back to Sydney.
The problem was the ignition timing we were using.
Never having done this before and not finding out what Norton used, we used the 38° BTDC recommended by Veloce for all Venoms.
However with the better combustion efficiency we were able to come back to 28° BTDC and all was well.
Sid Lawrence was an A grade rider ( Australia used a grading system then for racing in all classes. The top riders were “A”, then “B” and “C” ). Keith was a “B” grader and enjoyed success on his Velocette. Sid Lawrence would regularly finish in the top 4 or 5 positions in the title races he contested.
Handling of the Velocette frame was inferior to the Norton “Fetherbed”.
At Bathurst, west of Sydney, NSW, which then had a slightly downhill straight of 1¼ miles long, the squish head Velo was timed at 134mph, Manx Nortons and G50 were in the 132-136mph range during title races.
Keith’s squish Velo from memory was timed at 128mph.
Tragedy struck shortly after with Keith’s untimely death while riding his brothers 7R AJS special at a private practice session at the Oran Park motor racing circuit south of Sydney.
The motorcycle was used on occasions by his brother Terry in conjunction with the 7R, but he soon retired from racing and the bike was sold to Ken Wall of Torquay in Victoria.
Ken rode it on occasions, but with no major success and just before his eventual death it was sold on to Velo club member John Davies with a broken crankcase.