12 replies to this topic

[revingtosh]

OK - ive whipped the head off the mini today, and it would appear that the bores are scored quite badly (

The engine was running very strongly, but was very smokey when cold. I would say that the smoke lessened once the engine had warmed up, although the idle speed increased considerably.

The bores measure 73.00 mm, so what options are available to me on the rebore front? You can feel the scoring with your thumbnail in one of the bores.
If a rebore is possible, what crank mods are needed?

Can anyone recommend a decent engineering shop near Widnes (not for from Liverpool)

Cheers,

Mike

[Jordie]

are you sure its 73.00mm? How did you measure it.

[revingtosh]

are you sure its 73.00mm? How did you measure it.

With a digital vernier mate.

[sven_2k4]

Eric Hammond in Queensferry! he did my 1275 rebore, crank grind ad all the skimming....excellent service and product

Sven ;o)

[Jordie]

73.00 sounds like an odd size to me.
73.5mm would be 1380cc using a standard crank.
0.5 isnt much, for a rebore so id be saying the block is scrap if that is the correct size at 73.00.

[philc]

was you loosing oil. you maybe able to get away with new piston rings

[Dan]

How will that help with scoring? If the scoring is deep enough to feel then all it'll do with new rings is smoke again. From the sound of it this has been caused by a cracked ring. I'm guessing that if you used a caliper and not a proper bore gauge you've only been able to measure the top of the bore and not the inside or check for ovality. If it really is 73.000 across the top of the bore already (73.00 pistons are available, it's not that unusual a size) then as above I'm afraid it sounds like it's scrap. You might get away with 74mm pistons, it all depends on how much wear there was to the bore before the scoring started.

[revingtosh]

Here are the pics, let me know what you think.

The grooves that have my finger next to them feel quite deep when you rub your fingernail across.

Mike

Attached Files

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•  IMG_2265.JPG   1.39MB   28 downloads
•  IMG_2267.JPG   1.26MB   29 downloads

[philc]

looks like your up to your max bore, not sure you will get another re bore

[Sprocket]

Doesnt look like its been offset bored either

It could be sleaved back to a size to regain use of the block

[Dan]

It's a bit close to the sleeving size for standard sleeves already. Standard sleeves for a 1275 need a 73.03mm clean bore and while that measures 73.000 at the top I'd imagine it's a fair bit wider further down because I've never seen a block so highly polished as that in the bores. Custom sleeves cost a lot of money. That deep vertical score definitely looks like signs of a cracked ring. By all means take it to an engineer or better yet a Mini engine builder but from what you've said and the photos I think it's going to end up as scrap.

[revingtosh]

Oh bugger! Exactly what i didnt need!

Does anyone have a tasty engine for sale?

Mike

[tnewson]

A digital calliper (Vernier) can only measure to an accuracy of 0.025mm.

To get an accurate reading use an instrument witch is capable of working to a higher tolerance.


tom