There has been some talk on the diminishing supply of good 1275 blocks which got me thinking about what Mr GR said about the quality of modern sleeves being grade 22 cast iron and giving a good seal , now if there are less and less good 1275 blocks and you have a good clean and unbored block and want to extend its life, you could sleeve it, yes this does reduce its capacity but you then use Forged motorbike pistons with a short distance between the gudgeon pin and the crown to increase the stroke and maintain torque , now in theory you could bore the sleeves as the next step in the blocks life but it's more likely you go to 10thou and standard pistons like Hypertec etc

Now if my thinking is correct ( baring a massive failure ) you should be extending the blocks life .


I,d be quite happy to hear from David Rosenthal , Matt Read , Scott G , Dr Mini , Mr GR etc if they think I,m on the right track and what problems/flaws there are in my theory



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yep,,, nothing wrong with high quality liightweight strong forged bike pistons

stroker crank &-or longer lighter stronger con-rods would be nice to suit too

it`s only money

But then one set of forged bike pistons i bought (for one particular engine) only cost me $120 ,,, do your homework tho cause most bike pistons have small diam gudgeons so bushes need to be made, & the lack of height of them makes for the need to have big stroke, &-or much longer rods,,, or shave the block down heaps

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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.

The problem with the supply/cost of 1275 blocks is why I concerntrated on small bore blocks with my head conv. So far I have destroyed 3 small bore engines but pushed them well beyond their limits. I would not do it with 1275's but 998's are cheap so are honda heads.
I have decided which way I will go for my next project engine.REVS !!!!!!
Rule No 1 as Matt said SHOP AROUND. You can find plenty of suff at a good price. Bike pistons are good, but matching into a mini block is a problem as Matt said. I just make my own pistons and rods.
It all comes back to$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$

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Research is the difference between speculation and investment. Anyone who copys some one else will always be second
www.minisprintgt.com

Dean, shortening the crown height of a piston will only increase the stroke if you fit a stroker crank.
And GOOD (uncracked) big journal cranks used for this purpose are getting rare..

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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.

Geez I wish I could do that.

Why don't you guys pool your resources and 'just' make your own blocks and cranks. Then there wouldn't be a shortage of good ones would there?

You could make them to take your twin cam heads while your at it...

Madmorrie

You can.
Havent you seen worlds fastest indian?

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Simplify and add lightness

You folk's commitment to these A series bottom ends is to be commended. Blokes of much lesser mettle opt for the easy option and just fit a modern motor......

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But he's thriving and striving and hugging the turns.

Righty Oh , back on topic , I think we have established that my theory is a feasible and viable way of extending a fresh unbored 1275 block,s life , now down to tin-tac's , obviously it does take some research and careful measurements , now as the Doc says big journal cranks are in short supply as well , so as Matt says it may be longer , stronger conrods only, and with a correct size forged motorbike piston with a larger gudgeon pin and short distance between the gudgeon pin and the crown all to suit the sleeved bore , and all measured so you don't have to shave the block to make it work.

So is the time/ expense worth it , of course it is , if you get your hands on a fresh unbored 1275 block and you sleeve it with the modifications we have discussed the next step in the blocks life is a 10thou overbore . And over the life of the block ( baring major failure ) the fact that you have a rebore " in the bank " so to speak surely the initial work is all worth it.



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Dean, before you start check out what it is all going to cost. You need to price up a set of liners, boring ,fitting etc. It's not cheap. You can just keep replacing the liners instead of re-bore, but re-bore is a lot cheaper.
It's not often when a engine blows up that the block is not damaged in some way.The cost of liners etc is then wasted
The next problem is finding all the bits to mix and match. As Matt and I know, NOTHING just fits perfectly. I have looked at fitting bike pistons but they have a short skirt and small gudeon pins. Fitting bigger pins is no great problem but one thing that worries me with them is the longer stroke eng and the conrod angle changes. This could put more side load on the piston. The only reason I would go with forged pistons is if you are building a boosted engine or one that you are going to rev the tits off.
The engine I am looking at building is short stroke and going to pull over 9000 . with a blower. Thats why I am making billet pistons.
It is very important to plan what you exactly want from the engine it terms of reliability etc. If you want a power house that is going to put out 200 at the wheels then a fully worked "A" series is going to be over its limit.

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Research is the difference between speculation and investment. Anyone who copys some one else will always be second
www.minisprintgt.com

Thanks David, thats more what I was looking for , problems needing answers , as this is a theory exercise not a project its good to start breaking it down to components.

Elliptical piston movement was something I had,nt started to think about , and I can see what you mean about the side loading.

As this is a " Block longevity theory exercise " final HP does,nt interest me at all, this also means turbo charging and supercharging is not included.



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You could just build a std 1275 then, and limit the rpm to 3000. It would last for ages!!

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68 Mini
70 Moke

better off just walking instead then the donk would last even longer hey???

It`s a bit like saying that accelleration would be far better by removing a whole heap of weight out of the vehicle right??? well,,, take all 4x wheels off & the car would be way way lighter yeah???

If you chose longer rods, then the angle the rod makes at any given position througout the length of the bore is far less making the side/thust loads on the piston less

But again,,, as everyone keeps suggesting,,, it`s all money.

sorry to say but there is no """easy-cheap""" solution,

that`s why i keep saying """spend the money""" but spend it in the right places, on the right items, to make a good """Package""",,, ---> 1415cc stroker with twin cam 16v turbo injected cyl head , with forged bike pistons & longer rods & & & & & Now we have a very reliable, very smooth, very fast engine, that "Should" last a very long time


easy-peasy

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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.

I think the first thing is the cost of a set of liners,fitting, boring etc.
I have a rough idea of cost but some one may be able to put a accurate price on it.
I am playing with some wet liners for a block[just another mad idea] and the cost for time does not matter.
I agree with you inregards to a long life for the block and if it is going to be basically std engine thats not thrashed then it should last for ever,but the mighty un-known could step in and !!!!!!!!!!!!!!!!!!!!!!!!!!

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Research is the difference between speculation and investment. Anyone who copys some one else will always be second
www.minisprintgt.com

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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.

As something of a hypothetical question here , while I know you can make pistons and rods (if you have the equipment and skills or can pay someone to do it for you) , would it be possible to turn up a super strong crank on a lathe out of high grade steel ?

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