Bonneville land speed record attempt - Part five

Perhaps it was always over-ambitious to expect the Triumph to be in world-beating shape for a land speed record attempt in August, but the pain in Ferg’s voice over the phone was obvious. The plan to have Custom Pistons in the USA tailor-make pistons for the extensively re-flowed head and combustion chamber had hit the skids. Their estimate of a 10.5:1 compression ratio wasn’t going to be enough, and manufacture would take at least six weeks. “With the bike due on a boat in June, there wasn’t going to be enough time for testing and development,” said Ferg. “So I made the decision to pull the plug and focus on 2019.”

Keeping it pinned

Sometimes these things happen for the best. It certainly seemed so, a week or so later when we caught up with Ferg for a more detailed catch-up. There was still loads to do, to power the 1970 Bonnie along on the salt, at 4,000 feet, at more than 106.4mph–the existing 650cc Pushrod Production class record.

With SCTA rules in ‘Production’ classes proscribing any alteration in appearance, nearly all the work was focused on the engine. Ferg and his engine builder–Graeme Cole of Red Devil Racing fame–decided not to create a fire-breathing monster, instead taking a conservative approach. It should be ‘fast enough’, and sufficiently reliable to endure testing and development as well as two flat-out runs 13,000 kilometres from home. The existing record holder had offered to build an engine but Ferg was adamant about ‘keeping it Kiwi’ as much as possible. Graeme is also a big fan of using genuine Triumph parts wherever possible.

Even with the postponement, there was no let up. Graeme continued the engine build, including the development of a better breathing system for the crankcases, machining for new metric bearings, gearbox work–the list is endless.

Piston trouble

Of course the pivotal problem was–and still is–the pistons. CP’s estimate of a 10.5:1 compression ratio was discouraging, but tuned Triumphs have always produced higher compression than that. From Norman Hyde triples to racing Tritons, many have run as high as 13:1. With the conservative approach taken on Ferg’s bike, Graeme is aiming for around 12:1. Looking for alternatives started with Ferg calling a mate in the UK at Powermax Pistons. The idea of using a standard ‘cast’ (rather than forged, which is stronger) performance part, building it up then machining to fit the valve-lift and combustion chamber shape of Ferg’s motor was floated before being filed under ‘unreliable’. Two other contenders are currently in the mix: JE in the USA and an engineering firm in Dunedin called Datum. Encouragingly, Datum works a lot with world speed record teams, and it would be great to have another aspect of the bike devised here in NZ.

Once the piston issue is solved, the machined billet crank (kept at 360º throw), Carillo con-rods and pistons will be off to expert balancer Bob Meade. Then, the Bonnie will be well on its way to firing into life once more and spending time on the dyno. We’ll keep you posted.