In recent months, an autobiography has been published by Dave Bennett, the founder of Perfectune (later YellaTerra) – ‘Dyno’ Dave The YellaTerra Story, Dave Bennett, 2018 (ISBN 978-0-949398-29-1). The book is an interesting read, and well illustrated. It tells the story of how Perfectune started out in 10 Bay Road Sandringham in April 1962, and includes some background on the grey motor YellaTerra head. From the book:
Stage One
Retention of the original factory sized inlet and exhaust valves, generally re-profiled or lightened in some way by machining, re-shaping and sometimes polishing inlet and exhaust ports and combustion chambers for smoother gas flow by hand finishing with high speed grinders and possibly some machining. Raising the compression ratio by machining the joint face. Final assembly generally would include stronger valve springs or inner springs to allow the engine to rev to higher speeds than that allowed by original valve springs.
Stage Two
Similar to Stage One. However larger inlet valves would be fitted to enlarged valve throats and seats, the benefit here would be that greater inlet gas flow would be achieved and better filling of the air-fuel mixture into the cylinders and greater power output at higher engine speeds.
Stage Three
Similar to Stage Two. However enlargement of valve throats to accommodate larger inlet and exhaust valves along with greater attention to port and combustion chamber shapes may be complimented with even higher rated, stronger valve springs.
For serious high peformance road or racing a more sophisticated approach is required, achieving even higher power. Most people thought a stage three head was what was required, however the higher cost would be hard to justify unless the engine was to be fitted with correctly chosen and matched components. Carburettors, exhaust and camshafts being the norm. A poor combination would almost certainly lead to disappointing results.
Most of the work was either on the good old original design, six cylinder Grey Motor Holden or four cylinder Mini Minor heads. These were bread and butter jobs and they walked out the door. Every completed head was painted a dark blood red, almost vermillion colour.
We supplied a few of Melbourne’s speed shops operating by then current Drag Racers, such as Graham Rose in Footscray, and Eddie Thomas in Malvern. Perhaps one of the most notable of these was the Norm Beechey Speed Shop in Brunswick operated by the then very high profile circuit race competitor. He used to pay us £2 each to paint the heads “Beechey Black” before delivery. We often had prospective buyers visit us and say “Nah, I prefer Beechey’s head, they’re much better”. The manager of the Beechey Speed Shop often reported that people knocked back their black heads and said that the Perfectune heads were better!
The photo below is from the book, and shows “a fully ported and polished, original Grey Motor Holden, stage three head similar to that used on my 48-215 drag racing car”.
- Grey motor stage 3 head from Dave Bennetts autobiography.png (810.38 KiB) Viewed 743 times
I gave Dave a call, and he confirmed that most of the heads produced were either red or black. Some yellow heads were produced post 1972 (when the YellaTerra brand was applied), though by then sales of the grey motor head had dropped off significantly (perhaps 3 grey motor heads produced per month compared to 50-70 heads total). Dave was also clear that Eddie Woods (noted in the posts above) did work for him, and is a quite experienced and knowledgeable cylinder head specialist. Dave does not recall Eddie being involved in the Perfectune/YellaTerra grey motor cylinder head development though.
The book also notes that Dave’s 48-215 Holden, running a Stage Three head, 3¼” bore, triple 1½” Sus made 151HP at the flywheel on Jack Wilson’s engine dyno in Moorabin. The YellaTerra valves made in the 80’s through late 90’s by Aisan had YT forged into the valve, though this was later discontinued when a new supplier was sought.
Cheers,
Harv