1301cc



the idea is to make the spacing between 2/3 the same as between 1/2 & 3/4, so move 1 & 2 0.015" towards the water pump, and 3 & 4 0.015" towards the oil pump. Spacing between 1/2 and 3/4 stays the same, but the spacing between 2&3 grows by 0.030"

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did I tell you that I won a trophy?

Original BMC oversizes were +.010, +.020, +.030 and +.040.
030 is still common for V8s etc not so common form Minis but yes this size is still available from some suppliers.

@kenno-
Nope most Mini head gaskets are made this size to allow big rebores.

Nope if doing it you need to move all 4 bores, 1 & 2 go .015" towards the radiator and 3 & 4 go .015" towards the clutch.
This makes the gap 2-3 the same as the other two.
If only going to 1360 it's not essential though. Both my 1360 and 1412 stroker have the standard spacing still.

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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.

1303cc actually

but it was pretty common back in the day, just not so much anymore

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No offence intended here but--> anyone writing a book about minis 30 years ago may not have experienced such worn or stuffed-with components as we are finding these days.

You should put your heart & soul into everything you do.

at 1380, without offset boring, the wall between 2 & 3 is 2.69mm, if offset bored, it's 3.45mm... 2.69mm is pretty thin

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did I tell you that I won a trophy?

I agree. It is good to offset bore when you go to 1360, but this is easier with some borers than others...

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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.

we offset any/every block whenever we have to bore them,,, even if it`s only a bit then it makes it closer to the mark for next time it gets bored

just common sense really

both of my 1510cc blocks moved 15thou out for the inner cyls & 25thou out for the outer cyls

some break through to the oil gallerys on the end of the block so we just plug em up with a mild steel rod lockited & punched in & then just offset drill em,,, clean up the protruding plugs inside the bottom of number 4 bore with a die grinder & you`re done

easy-peasy & we`ve been doin it this way forever,,, since about 5 million years ago

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No offence intended here but--> anyone writing a book about minis 30 years ago may not have experienced such worn or stuffed-with components as we are finding these days.

You should put your heart & soul into everything you do.

it is common sense - I've only just found a machine shop that can do it, my usual bloke's machine can't do it so I've been sticking to 1330's.

I'm running out of blocks, and it seems that the entire world is out of +.040 and +.060 Hypatecs.... my last spare block is standard bore, so I could go .020", but I wanted offset that from the start by going to .040

I can get my current +.060" taken to +.114" with 0.012 on one side and 0.042 on the other... going to .094 only gives .002 so wouldn't give a lot of room for error to my machining man

what do you reckon?

existing .060 out to .114 with .015 offset

or

standard out to .020 and offset it next time? (even .005 offset only gives machining man .005 to play with)

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did I tell you that I won a trophy?

Excuse my ignorance - having a deadhead moment!

So if we offset the bore in the example simon and kev used the bore grows 15thous towards one end and 5 thous towards the other- instead of 10 /10. (yes???)

what has to happen to accommodate this shift in centres- rods/crank please.

Cheers Darryl

HI Simon
I have 72.5 mm pistons which is .070 over size to give the blocks one more bore size.
Graham Russell

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"It's better to be not informed than ill-informed"

The rods have about .030"? each way side clearance to the piston bosses- so the pistons will just move sideways .015" or so.
You need to eyeball them after assembly but clearances are usually OK.

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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 have been fitting Mazda poisons to My Mini Engines since the early 80. It started as an experiment when building a stroker engine because of their deck height. I have built them using 73, 73.5 ,74, and even 74.5. I always got my boring done according to the specs on the David Vizard Book. Never had any problems using the Metro Turbo Head gasket which had larger diameter firing rings and has re enforcement between 2 & 3 cylinders where the engine runs the hottest as there are two exhaust valves side by side. This also turned out to be a very good piston to adapt to a Mini Engine. Racing Speedway, Mini engines do a fair amount of high revs.

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DID I MENTION THAT I AM THE BEST SUPPLIER FOR MINI ELECTRICAL PARTS AND REPAIRS?
"Let us remove your "SHORTS"

What kinda Mazda? I was told the pistons in my 1380 are from a Mazda 808 but have never bothered to check it out.

one of the problems with Mazda pistons is they have fairly Thick rings

& another is the material takes a beating on the ring lands when you start running them with hi-comp ratios & hi revs

edit--> i`ve never run them myself , but i know plenty of people who have, hence why i know of some of their problems

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No offence intended here but--> anyone writing a book about minis 30 years ago may not have experienced such worn or stuffed-with components as we are finding these days.

You should put your heart & soul into everything you do.

hi, i would like to also know which type, as i have a set of rods that have bushes fitted to take mazda fully floating pistons
apparently it was also a speedway engine, but i think it may of had piston problems as Matt mentioned hence why these parts were sold
want to use these rods in a street engine so these pistons should be OK

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