AMC head failure! Carnage!

[silverbullet]

Si at T3 volution passed this one to me for a postmortem under the bandsaw, so before I hack it up to see if the waterjackets are really any better (or worse!) than OEM, what do you think did this damage?
(Your starter for 10: it is not corrosion damage)

[bigherb]

Nice bit of detonation there.

[R0B]

Is LPG involved perchance.

[itchyfeet]

Got some heads like this myself
I think it's been driven with a water leak into the cylinder, steam errosion

[silverbullet]

I was going for detonation (lean mixture and uncontrolled burn for those unfamiliar with the term), there is some vapourised alloy deposited on the edge of the barrel fire ring.
It has clearly propagated from the spark plug, no idea if lpg was involved.
I have only had one engine that suffered steam erosion (VM 2.5 TD intercooler, head cracked between the valve seats) and that simply resulted in severe pitting of the iron cylinder wall above the top piston ring.

[BOXY]

Looks the same texture as my RD350LC's piston. I had steam out of one exhaust and this is what the crown looked like probably after less than 30 miles.

[itchyfeet]

The reason I'm thinking steam is because two of the heads came off one engine which I know was run ( not by me) with a reassembly that consisted of reusing all the old seals including compression rings without even so much as a cleanup The only new seals were the water jacket and they had no Dirko.
Water in sump and almost certainly leaking into in bores.
I bought it as failed head gaskets but I was clear some muppet had been at it just before.

look at the state of the compression seals on the top photo, looks like was leaking from rhs.

I asked this question before on here or BY and got no difinitive answer but google image steam errosion and you get similar pictures.

Also note the heads are clean of soot.

[itchyfeet]

oh look what I found, somebody called silverbulletuk

http://www.thesamba.com/vw/forum/viewto ... ?p=6705400" onclick="window.open(this.href);return false;

It's very hard to say what has caused all the erosion and pitting; it could be detonation, piston debris or steam erosion. I have had non-VW engines that have had slight water ingress (when hot) due to cracks between the valve seats and they leave a very similar pattern of destruction. Is the top of the barrel pitted above the top ring witness?

[silverbullet]

Sometimes it's good to share one's experiences....
There is certainly a lack of petrol combustion deposits aka "carbon" so you may well be right.

[weimarbus]

for a newer head than OEM there seems to be quite alot of corrosion on the rubber seal face also, nothing to do with the combustion chamber but does it indicate poor quality alloy?, just concerned incase I have to use these heads in the future.

[silverbullet]

I think that depends on how they are assembled. Use of Dirko or Reinzosil is essential.

[silverbullet]

That samba post was two years ago!!!!
Of course I have now had 98mm pistons made for an 82mm stroke and standard rod length....

[silverbullet]

FWIW... a late VW (Germany) head weighs ~5390g vs. AMC at ~5780g

390g suggests a significant increase in density.

Both with valves and springs, no rocker gear or cover clips/bales.