Man with spanners - thinks he's a mechanic

[SteveRST]

Wow, that's not so much a crack but more life a rift valley!

Lucky that the bores haven't been scratched to fcuk.

[Dick]

Has this engine run boost

[ChrisL]

Yes it has

[Dick]

Think thats why pistons are like they are , maybe a little to much boost at some time 1 piston could be bad luck but with them all having damage i would put money its over boosted

[ChrisL]

I can see why you'd say that, although I think it's probably a combination no coolant, engine getting up to 114 degrees and too much advance!

I'd have to dig out the logs but it didn't get that much boost, I think I got up to around 11 psi...

[Jay]

Pulled many an engine apart that have had extreme overheating, coolant issues timing and fuel issues and have never seen 1 piston fail like yours as a consequence.

What has happend tho is i told dad he was wrong about something once and it slapped me in the face because he was right. Just saying. With the hundreds of engines incl race engines incl penskee indy car engines with the kniwledge he has hes probaly right again

[ChrisL]

Haha fair point Jay!
Just wondering if the combo of issues could mean that over boost was reached before it should have

[Dick]

Overheating damage would show on the side of the pistons the black coating that is below the rings , this is the point that the piston is it widest so this is the face that grabs the cylinder wall so the coating would be badly damaged . Ignition advance will cause damage to the top of the piston and above the top ring it would look like it has be chipped away or sand blasted very aggressively normally more on the exhaust valve side of the piston to. Cracking or damage to the ring area is a common sign that the engine has had excessive cylinder pressure caused by boost spikes excessive load causes the ring glands to crack or split . This is why boost pistons and diesel pistons have wide areas in between the piston rings to support the extra forces excreted on these areas. 114 deg is not hot for a engine

[Dick]

Just saying what i have found over a few years

[ChrisL]

Thanks for the insight, I guess I’m going to have to re-think my pulley sizing