1600 8V Vauxhall rally engine piston problem

[nova1600]

Guy,

I wonder would you give you opinion on what happened to my engine at the end of an event recently. To give some information, I missed a gear twice on the same part of a stage. Fuel was std unleaded with no octane boost and I was also on the rev limiter a fair bit at 6900 rpm.

There was no damage to the head or damage to the block. As you can see Piston 3 was burned and a bit of the side is gone from piston 2.

Thanks and Regards

[Guy Croft]

That is classic detonation, piston with 'speckled' crown (flecks of metal are from the piston), the edge of the piston has started to crumble, the pressure wave has cracked the ring land.

Causes - CR too high / fuel octane too low, ignition over advanced, inlet air or engine too hot, running too lean.

See also: http://guy-croft.com/viewtopic.php?t=97

GC

[nova1600]

Many thanks for your reply Guy, we will investigate further and let you know how we get on.

[dvv]

Many thanks for your reply Guy, we will investigate further and let you know how we get on.

Same thing happened to me as well, only MUCH worse, I had about an inch's worth of piston missing. And that was a Fiat Uno Turbo piston, operating without a turbo, strictly atmospheric.

In my case, the obvious reason was terrible local fuel, coupled with a strong CR. Serbia has what must be the worst fuel in Europe, bar none; nominally lead free 95 octane managed, in a recent random test, an average of 91.8 octanes. I would imagine most of the required additives were also missing.

One more factor may also play a part - too many load/unload stages between the refinery and your fuel tank. Theoretically, this should be a single stage, load in the refinery, unload at your petrol station. But in practice, extra stages can sometimes be added, and you have no way of knowing or finding out.

I suggest using a series fuel filter; a rougn one as a pre-filter, and a fine one as THE filter. That's what I do, and I exchange the pre-filter every 3.000 miles or so. You'd be surprised at what you might find inside.

Careful about selecting them for flow.

thank you,
DVV