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Bore sleeving
#1
Having run our new improved sporty engine for five hours on the test bed we had a short spell of uneven tickover for about 2 mins followed by a total conk out. Having spent some time looking at things discovered we had water in number 2 bore. Now we have popped the head off I can see a tiny pinhole in the bore wall which was not there before or at least very well hidden. I have had a poke and despite my careful attention when boring the block in our milling machine can summise there is a large pit on the water side caused by corrosion leading to a tiny pinhole. My thoughts then went to sleeving the block and was wondering what is the best way forward. I can find a few different sleeves available but most are quite thin and would leave almost no material at the bore size I require. My understanding is when sleeving 2mm each side is good and 1.5mm minimum. I was wondering what other people have used sleeve wise.

Later design 2 bearing engine, just over +70 slipper pistons, pheonix crank and rods, trials cam and big flowed inlet valves, using an older screw coreplug block. One slightly miffed owner after all the work we have put in. I guess we have been lucky as another few mins of testing I would have shut the engine down ready to fit the engine then taken a couple of days off to fit. I guess finding the issue out of the car is a small blessing.
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#2
I would not recommend boring A7 cylinder liners past +50.


Better to buy a set and bore to standard.
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#3
Be aware that fitting liners creates a weakness across to the centre stud. Unavoidable but something to look out for.
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#4
That is very bad luck but at +70 things were going to be getting a bit hairy, particularly for a trials motor that will be revving continuously.

I have to agree with Ruairidh, I’m afraid.
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#5
Years ago I sleeved one bore of a +80 block with a liner I got from Westwood Cylinder Liners. Sorry, I can’t remember what it was just know it wasn’t a standard Austin liner. Westwoods have a huge catalogue of parts and I just picked one that was going to give me the same wall thickness as an Austin one at standard bore. It worked for years on a race engine and wasn’t the reason I stopped using it. You do have to be a bit careful, the required bore size doesn’t leave much metal at the base of the block. I don’t think it would stand all four done like that. It depends,really, on how much you want to save that block- mine had a lot of porting work done on it. If it’s a standard block it would be far easier just to get a new one.
Alan Fairless
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#6
(13-12-2023, 09:11 AM)bystander Wrote: Be aware that fitting liners creates a weakness across to the centre stud. Unavoidable but something to look out for.

As the wise owl said, "To Wit".

I think this block is a write off...

   

   
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#7
I  personally would not bore a linered block over +40.
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#8
(13-12-2023, 07:14 PM)Robert Foreman Wrote: I  personally would not bore a linered block over +40.

Me too.

Steve
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#9
I had a block that ran well on +80 nos 1,2 & 3, with a liner in no.4 bored +20. And had the liner fitted for the same reason you mention
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