Pulled the head off my motor yesterday and I think I've had a blown head gasket between 1 and 2. What do you think?



The bores have marks in them but I can't actually feel anything when rubbing my fingers across the marks except in the area I've circled. Pistons are 40 thou over.





What's the prognosis?

Looks like rust marks from water getting in the bores. Easily explained if your head gasket was blown. Do you reckon the marks might be surface rust it's hard to tell from here but they sure look like it?

If it is then maybe just a new head gasket and head surface grind for good measure.

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SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.

Yeh the marks do look like they were created from liquid almost like an acid.
The car sat around for about five years maybe some moisture has got in and marked them. There doesn't appear to be any scores going up and down the cylinders.
Coincidently these marks are in No1 and No2 cylinders same cylinders where the head gasket has been blown.

By the looks of it, a quick hone would clear that up nicely.
Definitely done a head gasket.
At the same time you can replace rings - the piston crown seems to be in very good nick.

The more I think about it, it makes sense that it was pobably surface rust but the rings have polished it up nicely so I can't really feel anything.
If it is honed do I put the same size rings in, currently the pistons are .040?

Yes honing will mean you can retain your 40thou pistons and rings.

I'm going to sleep soundly tonight,

Thanks willy

dunno...but this looks like a gudgeon pin may have stepped out of the piston....just like the one currently on my garage floor...

Why are the bores so dry....when did you say you pulled the head off

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"Show me the Mini!"

The photos were taken the day after I pulled the head off and I wiped them clean.
The engine hasn't been started for about a month or more.

Well I would get some oil in there and turn the engine over by hand once....cover the exposed pots with an oily rag and simmer for several weeks Repeat until golden brown Nooooo thas what you are trying to avoid....surface rust in the bores.

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"Show me the Mini!"

They do look a bit S/H to me- having gone this far, I'd bore & hone it and fit new pistons...

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

I spoke to a local engine reco bloke today and I'm going to take it in to him.
He said it could be just water marked. Currently the pistons are 040, if I did bore it 60 will that be its last rebore?

Can someone tell me the proceedure for fitting new pistons?
I just finished reading GR's article in TME on building an 1100, how timely I thought
Little hints like "making sure the circlips go in the right way" are priceless.

Take it to someone who knows what they are doing.....watch them and learn....on the other hand, have a go yourself if money is no object.

A long time ago....I was packing it when I fitted new wet sleeves, rings and pistons to a Renault once....I need not have worried....all precision parts designed to fit together....unlike a Mini

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"Show me the Mini!"

I cannot stand closer to 9Y's recommendations.

If you don't know what you are doing, you shouldn't be doing it at all.
PLEASE for the love of god take it to a specialist.
By all means, have a crack at it, but expect a ****.