Dave Plowman (News) wrote:
In article ,
The Natural Philosopher wrote:
I've been around long enough to know that most who find differences in
petrol are fooling themselves - unless using too low an octane rating
for the design of the engine.

Quite right. The old A series high comp engines in midgets and the like
worked better on 5 star, especially once you got them to breathe a bit
better and sorted out the timing a bit.

Since I had a two 1275 Midgets, I'm quite well up on that engine. I've
also totally re-built several.

Neither of mine was 'better' on 5 star. Of course if you modify the
engine, you're starting a new ball game. But that's not what you said
originally.

They WERE designed to work on 5 star. Especially once I had finsished
with em.

By 'working' on them it would be possible to make them only suitable for
aviation petrol. Or to run on 2-star. But that's not what they were
designed for - my point.

They WOULD work on 4, with slightly retarded ignition, to stop them
knocking, but they weren't as good.

Mine both ran on standard timing. And didn't pink on 4-star. Perhaps your
timing technique or timing marks were inaccurate? Or perhaps they just
simply needed a de-coke. Also, a slightly weak mixture encourages
detonation.

Mine din't pink on 4 star. They juts ran better on five thats all.