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A new way of spec'ing Cams: Speed Spec.
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A new way of spec'ing Cams: Speed Spec.
nissan, PolyQuad, two Valve head, head, David Vizard, engine Builder, low torque Speed, Cylnder Motion, head design, ignition, ffour valve per cylinder, GFN readers, engines, Honda engines, bob, Austec
Written by David Vizard on 11 Jan 2012
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A revolutionary, fast and hyper accurate way of spec'ing and selecting catalog cams; A system that finally eliminates the fog of cam selection.

The revolutionary (and I seriously mean revolutionary) cam specing technique that I am about to show you is at least 12 years late in arriving at the desks of pro and pro class enthusiast engine builders desks. All because somebody said “we have some clever guys working for us you know”.

Here in simple terms is what it delivers:

Speed Selection - 15 second cam selection.
Speed Timing – dramatically more precise valve events

“Speed Spec' for catalog cams did not suddenly materialize out of near thin air. In essence it is a simplified high speed, paper friendly offspring of my immensely functional 'Cam Master' program. To better appreciate how 'Speed Spec' came into being I need to fill you in on the genesis of 'Cam Master'.

Cam Master Genesis

Cam Master is a computer program that very accurately determines what an engine needs in the way of valve events (opening and closing points) for optimal results from the particular spec of engine concerned as opposed to a generically similar one. It has its roots far back – in fact over three decades before a fully operational Alfa program was up and running.

Way back when I was a new student to the science of engine development (late 1950's) I wondered why engines would have differing optimal valve event timing. What, I asked myself, were the factors involved. Well back in those days I had much else to concern me as far as my education on developing engine performance was concerned. I had already built a crude but effective flow bench which was teaching me heaps of go-fast tech in terms of cylinder head mods. It was not until successful and nationally recognized UK engine builder Harry Ratcliffe of BVRT happened to mention to me that he had noticed that the short stroke big bore Ford 105E range of engines generally like to have the Lobe Centerline Angle at 109 degrees where as the long stroke 'A' series engines that powered the Mini Coopers of the day were more disposed to 104 or so. This comment from Harry was actually what got me started on my quest to find out what factors affected the optimal opening and closing points any particular spec of engine needed for the strongest power curve in the desired rpm range.

All the forgoing was back somewhere in the mid 1960's. Over the next 30 years my involvement in the cam aspect of engine development became ever deeper and more involved. In 1971 I began, as an outside consultant, working with the UK division of Chrysler, or more accurately their competition department. That year they introduced the then new-from-the-ground-up Avenger. Loosely my job description here was to popularize it as a performance vehicle. That was all very well but there was almost no speed equipment in existence for this engine and certainly close to zero know-how on what was needed to make it perform. I went to work investigating this somewhat unorthodox engine and making modifications accordingly. My efforts here rapidly outpaced the factories. They must have liked my efforts because the first simple projects lead to more ambitious ones. Eventually I was developing an ultra wide power band version of the production line Avenger engine and a turbo version of such to put Ford's Lotus Cortina twin cam in it's place (i.e. behind an Avenger). As it happened I pulled off both projects with apparently great success. Motor magazine tested my ultra wide power band Avenger (useable power from 400 rpm to 8000 and I am still waiting for a VVT engine to match that). Even at 1500 cc it whooped the butt off the newly introduced 1600 Cosworth BDA Escort in every respect. The differences were far from marginal, and, as the magazine's road test editors put it, embarrassing for Cosworth. As for the Turbo Avenger this project went very well producing an emission legal 0-100 mph in 13 seconds. Since, at that time (1972), I had zero experience with turbo motors I thought I would seek some guidance before starting this project. This, for you older folk, was the era when the Turbo Offy's made their mark in Indy Car racing. One of the prime movers in this respect was Ak Miller. So in January of '72 I left the freezing whiles of England's Cotswold hills and headed to the summer-like climes of LA California where I met up with Ak Miller. I have only met up with Ak once since then but he made a lasting impression on me. I am sure had he not been such a great engine and in particular turbo guru he could have made a really outstanding living as a comedian. Ak was a very likable and dynamic character. The info he so freely gave me in 8 hours (along with breakfast, lunch and dinner) on the ins and outs of turbo motors was to stand me in excellent stead in my quest to build a world class turbo Avenger.

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