my last broken engine....(probably not least)

[filh]

Here's my last victim . 1st cylinder Piston, with little damage.....
Block is of course out too . Piston are ...were .50
It's an used engine , I bought . it was rebuild and had 20.000km ( Seller's saying) Made 500km with it (one rally race) .
I have a strange feeling . I broke 5 engines , but found each time broken pistons (between rings).
I didn't rebuild the last one (bought used ) , but broken piston is the same diagnostic.
My machinist thinks about ignition timing problem , at high revs .
Timing is always well adjusted , following the Toyota tuning rules workshop manual .

As he once tested it before , at about 5500rpm , he found 44° timing advance . Much too much for him . Engine was not in charge .The machinist told me there's not much difference in charge ..

My question is : Have you ever heard about bad computer unit giving too much timing?????

My trust is fading away each time I break a 4age (always blue top )

Thanks for helping
Phil