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melted a piston a thread by white90


geoffbeaumont
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white90

70mph on the M5 then load noises/loss of power/lots of smoke then no go :(

3 days later sees the 90 back up and running

much thanks to good mates.

slave cylinder/gearbox mounts/lift pump were just a few of the extras needing attention

back to normal power levels and consumption figures.

diagnosis showed this:

So what happened to it?

post-5-1189484263_thumb.jpg

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That’s a bit unfortunate Tony :blink: ……….. but at least you seem to have effected repairs quite quickly.

Please don’t take this the wrong way ………. Its only an idea……

What was the EGT ? ……………….. I am still not convinced that the 300 can withstand extra boost mods that shove up the EGT by a fair few degrees …………….maybe the short term is OK, but what you have witnessed maybe the longer term damage ? I hope I am wrong, but that is the sort of evidence I would be looking for.

:)

Ian

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Ian

EGT max was 694

now max EGT at totally standard settings is 634

when it went bang it was 670ish.

running 18psi with a bit of extra fueling.

the cause wasn't obvious so your thoughts are most welcomed

repairs took 2 days and a bit of tidying up time today. to collect parts etc

the piston was fairly damaged/melted squish area and the side damage was the cause of the demise.

my old engine is to be resurrected with +20 over size pistons a rebore etc

the big ends had gone through the white metal into the copper.

parts etc so far have come in at £320 with some machine work to go

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Looks like either one of two things...

Leaking injector/injector fault.. or a coolant leak.

You can get a similar fault when coolant is allowed to drip into a cylinder, but more likely to be a injector problem.

I'd get the injectors checked!!!

Ian

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Ian

EGT max was 694

now max EGT at totally standard settings is 634

when it went bang it was 670ish.

running 18psi with a bit of extra fueling.

the cause wasn't obvious so your thoughts are most welcomed

repairs took 2 days and a bit of tidying up time today. to collect parts etc

the piston was fairly damaged/melted squish area and the side damage was the cause of the demise.

my old engine is to be resurrected with +20 over size pistons a rebore etc

the big ends had gone through the white metal into the copper.

parts etc so far have come in at £320 with some machine work to go

Sorry to hear you've been having problems Tony. At under 700 degrees your EGT isn't excessivly high - I could get 650 fairly easily with a standerd 2.8 TGV.

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my old engine is to be resurrected with +20 over size pistons a rebore etc

the big ends had gone through the white babbit metal into the copper.

parts etc so far have come in at £320 with some machine work to go

Dont skimp on the machining .................. I can throughly recommend the shop that did my liners , but they are not local (Winchester)............ I guess I would expect to pay about £300 ish for the Crank regrind, Rebore, and head skim.

Yes, I would have expected the shells to be showing copper at 143K !

Again, for longevity, use the best possible components for the build ................. shells from Glacier or Vandervell ............... pistons, I guess. will be OEM as will the rings ............. I'm a big fan of chilled Iron moly chrome rings ............. but then again I'm a pertrolhead and not an oil burner guru !

:)

Ian

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