13 replies to this topic

[minilee94]

As it says really sent my engine to a machine shop and thu rebored my block to a 1380 but how do I tell if they actually offset the bores or not as they said they had set my CR as 10.5 and they didn't it was at like 9.5

[minilee94]

Anyone

[Cooperman]

You need to know what the standard bore centre dimension is between cylinders 1 & 2. Them, if it has been offset bored that dimension will have increased by between 0.030" to 0.040".

I don't have that dimension to hand and I don't want to have to go and pull a 1275 block from my storage area this evening. However, if no-one else has that dimension I'll do it for you on Monday. Just let me know.

You will need a digital vernier calliper to check your block.

If it has not been offset bored, the only real solution is to have it sleeved back to a standard 1275. It would be very expensive and possibly impossible to have a block which has been bored to 1380 but not offset bored sleeved and bored offset. When I encountered a 1380 which had not been offset bored, but had been incorrectly bored 0.005" oversize for a 1380 it scrapped the block for economic reasons.

A 1380 which has not been offset bored will continually blow head gaskets.

[Barman]

Take the head off and post a picture....

[Cooperman]

You mean we are going to GUESS!

No, it must be measured.

[ACDodd]

Usual offset bored 1380 blocks have the same spacing between all bores.

It all depends on how much it has actually been offset if at all. It needs to be measured to determine what has actually been done.

Ac

[Barman]

I stand corrected... again....

[minilee94]

Yeah if you can do that for me cooper man that will be great I did tell the machine shop to do it but I did also tell them to clean the water galleries out and work my CR out and they didn't do I just wuna make sure

[Cooperman]

If they have bored it to 1380 without correctly offsetting the bores, then they owe you a new block and another lot of machining at no cost to you.

I'll measure on Monday as I'm out at a rallying-book launch at Chatsworth House all day tomorrow.

[minilee94]

Okay thank you soo much Pete and yes they do indeed iv just had cam timing done block skimmed etc so I really hope it has been done

[Cooperman]

A guy who runs a Mini Club asked me to look at one of his Minis. It had been bored out to 1380 and fully re-built. He had had the engine done over 2 years before, but when he finally got around to fitting it the thing threw oil out through every breather. It even spewed out from the back of the bonnet and went over the screen.

There was smoke pouring out of the oil filler hole in the rocker cover at tickover. So the engine was removed and stripped. On close inspection I found that the block had not been offset bored, despite a local engine re-conditioner doing the work. In addition, all the bores were at a minimum 0.005" too big which had caused a 'ripple' effect on the bore walls as the pistons 'rocked'.

The engine was well out of warranty, and the only way ahead was a replacement block, a new set of rings, proper offset boring to the correct size and another full build. It was not cheap!

Mini engines need to be built by Mini experts as these days not many machine shops fully understand old technology A-Series stuff, unless the machine tool setters & operators are 'old school' time-served guys.

[minilee94]

Yeah I see we'll the engineering firm is an old school aviation engineers they deal with planes I jut need my mind out at rest . On my block there is loads of meat between all bores and equal meat too I know you said it needs measuring but I'd thought I'd say anyway

[Cooperman]

It is most probably correct, but it won't hurt to measure it. I'll get the standard bore centre between 2 & 3 on Monday when I'm in my workshop.

[minilee94]

Okay thank you pete also it's an a+ if that helps anything