i was given an engine and are at the stage of pulling it down and replacing the rings and bearings and came accross these on each piston has it been bored out 40thou?? oh and my brother believes that it has been pocketed
here are some pics






damian

Yes it has been bored 40 thou oversized and yes it has also been pocketed (the little round cuts on top of the block) to allow a big valve or 1275 head to be used on it . It's a 998 isn't it ?

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no its an 1100 and i thought that it has been pocketed to fita 1275 head just making sure

Yes , I should have said 998/1098 meqaning not 1275 , having the block pocketed like that gives the 1275 valves room to move without striking the top of the block and costing money ....

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Pretty rough pocketing job it looks like, particularly #3- I'd redo them... just trace around a 998/1098 gasket.
Neatest way to do this job is on a mill.

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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 am just going to fit an 1100 head on it nothing special was just curious about it thats all my brother is trying to get me to do up a cooper s head put it on it and put a bigger cam in it

I came across this in "British Leyland Mini's , Maintenence , Tuning and Modification" by David Marshall and Ian Fraser ,



Pretty simple cutter really , so long as your brazing skills are up to it . Presumably this wouldn't be too kind to the valve guides either as it would take a bit of grinding to get down far enough but it would sure make it easier to get the pockets in the right place since they are directly below the valves .

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Brazing... pffft. Just arc weld some HSS toolbits on, I do it all the time to make cheapo boring bars for the lathe.
It welds pretty good, whether you use stick or MIG.. but the welding books don't tell you this.

Now kiddies... back in 1968 I did the job in the car with the head off, using a Black and Decker drill and a few mounted stones. The `depth gauge' was a steel Vegemite jar lid sitting on the piston, .100" down the bore..
To get the grit out I wiped grease round the top of the bores and turned the motor over, repeated until grease stayed clean.
Don't try this at home these days, Vegemite lids are now the wrong size, and are plastic...

BTW the 1220 motor absolutely flew with a 1275 head on.

<edit> as the valves are on the C/L of the block, it's real easy to mark out the recesses using the exhaust side of a smallbore head gasket.
No recesses are needed for the inlet valves.

For a good `how to' on this mod, read Des Hammill's book "how to power tune the BMC/BL/Rover 998 A series engine".

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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.