What caused my melted piston?

[MikeyFIN]

The 10PSi light goes off at around 20-30mph so I guess it should be higher than 15PSI at 80mph+

so you are in fact guessing Tomas....
Damn you, get a meter there for it ASAP...

The warning lights are aka IDIOT LIGTHS...

[Tomas Wallin]

Valves looks good so no blowby´s on the seats that´s what I was after.
I stick with the air pocket issue.

Not an ignition crossfire like Daredevil hinted as a timing problem ?
Those seems to be the only 2 reasons which could lead to detonation IMO as the plug hasn´t blued or anyother part to speak of.

New (since 20hours) Keith Eickert plug wires, new MSD crab cap distributor, MSD AL6 box and MSD coil.

Wouldn't it take a while to blue the plug? All this happened within a very short time period.

[Chris]

Detonation almost always fractures the tops of the pistons around the ring lands. How about a cam lobe?

[Tomas Wallin]

so you are in fact guessing Tomas....
Damn you, get a meter there for it ASAP...

The warning lights are aka IDIOT LIGTHS...

I have a gauge for it but's that's on the IC. I rather have lights than too many gauges.

[Tomas Wallin]

Detonation almost always fractures the tops of the pistons around the ring lands. How about a cam lobe?

Wouldn't think so, engine runs since I put it together again. RMBuilder cam also new since 20hours.

[Chris]

On a long term cooling issue yes.

I've seen them go in seconds. At max power and losing cooling water, you have no way to draw heat from the valve (exhausts valves sink heat through the seats).

Having said that, are you using the proper head gaskets for your block? There are passage and restriction differences between Mark IV and Gen 5/6 blocks.

[Chris]

Wouldn't think so, engine runs since I put it together again. RMBuilder cam also new since 20hours.

If you had lost a cam lobe you'd have noticed it on reassembly. I'm assuming they're hydraulic roller cams.

[Chris]

Wouldn't it take a while to blue the plug? All this happened within a very short time period.

Max power, max RPM- the damage takes a couple seconds.

At 6,000 RPM your engine is experiencing 50 combustions and power pulses per second. Imagine smacking your thumb once with a hammer. Now imagine smacking it 50 times in a second.

[MikeyFIN]

How did you Route them wires I Think You do know this but repetition is the key ?

It would take a while to tulip a valve or blue anything which IMO isn´t the case here.

[MikeyFIN]

detonation almost always fractures the tops of the pistons around the ring lands.

agreed.

[MikeyFIN]

I have a gauge for it but's that's on the IC. I rather have lights than too many gauges.

So that makes you an..

[MikeyFIN]

I've seen them go in seconds. At max power and losing cooling water, you have no way to draw heat from the valve (exhausts valves sink heat through the seats).

Having said that, are you using the proper head gaskets for your block? There are passage and restriction differences between Mark IV and Gen 5/6 blocks.

Yes you could do that but there´s problems arising IMO already for a while..you just notice it in seconds, That´s my take. And yes I´ve ground a FEW Valves to know how they work... but anyways repetition is the key here for everyone.
It´s like detonation... a 50$ hearing aid modified is a lot better (read sooner) detecting detonation than any knock sensor..

[MikeyFIN]

Max power, max RPM- the damage takes a couple seconds.

At 6,000 RPM your engine is experiencing 50 combustions and power pulses per second. Imagine smacking your thumb once with a hammer. Now imagine smacking it 50 times in a second.

Howabout the forehead instead

[MikeyFIN]

Still we haven´t come to an agreement of the cause...

everyone put their take and reasoning on it behind ?

[Tomas Wallin]

I've seen them go in seconds. At max power and losing cooling water, you have no way to draw heat from the valve (exhausts valves sink heat through the seats).

Having said that, are you using the proper head gaskets for your block? There are passage and restriction differences between Mark IV and Gen 5/6 blocks.

The head gaskets are Fel-Pro MLS 1075-1, Merlin II block and GM 088 heads.

New impeller, sea strainer that was clean and water was flat.

[MikeyFIN]

Tomas it doesn´t matter ..sometimes for example big diesels have to use a water softener that takes out the surface tension because otherwise they would knock a hole in the cylinders.. the Ford Powerstroke for example is notorious of that.
Air pockets just come sometimes and there´s not much one can do about it.
Lack of water somewhere is the only reason I can think of that raises the combustion temps so that detonation would occur if everything else is fine.
The other reason is a misfire that spikes the temps and just ignites the detonation cycle.

[Geronimo36]

I'm going with pre-ignition of some sort. How did the rod bearings look?

If it leaned out I would think it would have melted the piston in the 1-2 pm location near the intake valve relief since it's the thinnest area on the edge of the piston near the ringland..

As far as being able to catch it or stop it...don't think there's anything you could have done, it happens too quickly... Having an A/F meter would have helped before you went WOT but we dont' all have access to that!

My $.02.

[MikeyFIN]

If it goes lean the exhaust valves will glow red...and detonate is there, that wasn´t the case but on the other hand no 6 is the leanest running cyl in a BBC.
Was there any carb tuning done at the dyno session ?
I don´t remember the dyno session ..you posted it somewhere didn´t you Tomas?

[Geronimo36]

I dunno, I don't want to dissagree but the valve relieve usually goes first on all the BBC's I've done it to.... The ring-land in the relief area is significantly thinner than everywhere else and it's also sharper..

I've blown a few up in my years from being lean and every single time it took out the piston in the relief area... 5/7 seem to be the worst, at least on the ones I blew up, by my own silly mistakes I might add..

[MOBILEMERCMAN]

Air pockets just come sometimes and there´s not much one can do about it.

You can ensure you have enough water pressure. Some add fittings to the rear of the intake too.