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MG MGA - Hole in the piston - blocked fuel filter?

One of our club members had the recent misfortune to suffer a "hole in the piston" during a club sprint event. His engine builder believes it has been caused by a partially blocked fuel filter causing the engine to run lean - maybe from vigorous cornering stirring up sediment in the tank - filter had a lot of gunk in it when cut open.
I thought holes in pistons were from too far advanced ignition, too higher compression or too lean carby setting - I never thought running out of fuel would cause it. The car was supposedly running fine up until the failure. (It is 1800 engine).
Any similar experiences?
Mike
Mike Ellsmore

Well when your running out of gas you are going to run lean.I would guess the front carb would run lean 1st.
gary starr

Not so much the running out of fuel otherwise the car would only run weak for a few seconds before stopping.

I think the situation has some merit if the following occured.

The fuel level in the carb/s has a direct relationship to the mixture and so a lower than normal level in the float bowl will give a weak mixture. This of course would also mean less fuel is being consumed and thus the amount of fuel required to run like this would be less. So a slightly blocked filter could give enough fuel to run but at a weak mixture and the engine would eventually melt a piston from detonation.

I think this is rather speculative and I personally would want to consider other reasons and test various hypothesis. The only place to check the reality is on a rolling road and that would be my first port of call.
Bob (robert) "Hence he is considered a valued contributer on flame wars" quote by Wyatt

It sounds like the dreaded "hole in the piston" problem that the mga twin cam had in the early years. This was caused by a combination of high compression and a lean fuel mixture. Both these factors had to be present at the same time for the problem to occur.
It was cured by removing one of the two factors. The factory lowered the compression ratio from the original 9.9 to an 8.3 ratio.
The owner/racers left the compression at 9.9, or even made it higher, and solved the lean mixture problem instead. This was done by "soft mounting" the SU carburetters by using a Weber O-ring between the carburetter and the manifold (or using Weber caburetters). The SU leaning was caused by an engine vibration affecting the fuel level in the bowls.

Severe detonation, due to a fuel with too low an octane rating, or over advanced ignition, tends to break up the piston on the top edge, above the first piston ring.

Mick
Mick Anderson

Can also be caused by wrong heat range spark plugs. Happened to me on a rally prepared Toyota back in the 70's.
Peter.
P. Tilbury

This thread was discussed between 20/10/2007 and 22/10/2007

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