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MG MGB Technical - Seen anything like this before?

A pal stopped on the Autoroute in clouds of blue and white smoke, so a blown head gasket was diagnosed. Swapped at a local garage, but while filling the radiator the sump plug was still out (oil contaminated so drained) and water started running from the sump!

Back home it turns out there is a circular hole punched through into the water jacket from one of the bores more than half-way down, about 1mm dia on the bore side and 3-4mm on the jacket side so seemingly punched through from the bore to the jacket.


paulh4

Crikey Paul
I've seen it plenty of times with diesels but not on petrol engines
I take it that it's a petrol engine - ?
If it's petrol ,Maybe some sh@t or an air bubble in the casting that has decided to live somewhere else all of a sudden
William Revit

Indeed it is, MGB to boot. Out of interest I've asked if they can measure the thickness of the casting at that point. They are going to sleeve it, but one can't help wondering if there are any other weak areas. Peter Burgess has told me that some Qualcast blocks were found to be so porous that they were sleeved from the outset.
paulh4

It would be interesting , to have a look at the block after it's bored before the sleeve goes in, I'm sure they'd let you have a look just to see if it was a one off bubble or a porous area--doesn't make much difference I suppose ,a sleeve will fix it but interesting all the same
William Revit

Hi Paul

Sad story. Which bore was it?

Poor Qualcast blocks was why so many Goldseal engines were linered back to std, you were getting a new block with repairs or the blocks would have been scrap!!!!!!

Peter
Peter Burgess Tuning

It's 200 miles away so I'm not going to get to see it, closer to you Peter than me :o)

No1 cylinder, and from the valve cut-out in the attached you should be able to work out where it is (fuzzy black dot near the bottom of the bore) in relation to water passages. I've asked if they can gauge the thickness of the casting at that point by poking a bit of wire through, out of interest.

paulh4

Several possible reasons.........

Murphy's Law:

If anything can go wrong, it will.

If there is a possibility of several things going wrong, the one that will cause the most damage will be the first one to go wrong.

If anything just cannot go wrong, it will anyway.

If you perceive that there are four possible ways in which something can go wrong, and circumvent these, then a fifth way, unprepared for, will promptly develop.

Left to themselves, things tend to go from bad to worse.

If everything seems to be going well, you have obviously overlooked something.

Mother Nature always sides with the hidden flaw.

Mother nature is a bitch.
LC

Happened to me once, but a 1972 cc engine so self inflicted. With 4 kids in the B (they were all little then) as well as us I thought I'd better limp back to base rather than wait for a tow. Coasted down hills to save thongs where I could. Mistake! The leak was getting worse and on the 2nd to last hill the bore got enough water in it to hydraulic. Shattered piston and split bore.
I had thought it was head gasket till I lifted the head and found the gasket intact and the small porosity hole in the bore, alongside the split.
The engine had done a decade of hard work, and the block was a converted land crab one so I couldn't complain too much.
Paul Walbran

What was it actually bored to?
Colin Parkinson

A few years ago I had a block re-bored. Within a few thou the tool hit sand inclusion in one bore. That needed linering.
Could have been a GG engine, but memory is a little vague on that!!
Allan Reeling

It is quite common for the big bores to break into where there is a mild steel strap in the casting between cyls 1&2 and 3&4 - that is why I always used to liner any big bore engines.
Chris at Octarine Services

Colin, if you're asking what bore for 1972cc it's 84mm
If you're asking what size the pinhole block of Paul H, I'd say going by the pics it's not far off std.
William Revit

Bill, I was asking what the bore size was in the pinhole block.
I always use liners in 1950, and get all rebored blocks pressure tested to ensure integrity. Colin
Colin Parkinson

It's just 'standard', +40.
paulh4

I got a shiny new 1.8 Marina as a company car in 1974. On the way home from Manchester it sprang a leak from the water circuit to atmosphere.
The car finished up at a local dealer who had to fit a new engine as the block was porous.
Its an ill wind, I had an MG1300 for a few weeks as a loan car, as ever I wish I had kept it.
Stan Best

This thread was discussed between 16/07/2019 and 22/07/2019

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