Gezo wrote:
Hi,
Another crank question.
I was reading an old mini magazine and it said,
If you use a LS1275 big journal crank (1.75 big ends), offset machine the big ends down to 1.625 diameter use this in a Cooper S block you will get an 1/8 of a stroke. Does this simply mean you just grind your LS crank down to 1.625 on the big ends and put it in a Cooper S block and you get an 1/8 stroke.
Thanks
You need to
offset grind the big ends to 1.625". This means they are set up in the grinder to take 99% of this metal off the inside of the pin, and bugger all off the outside. This moves the reground pin's stroke radius outwards.
Then you use S rods, but they are too wide and must be narrowed to fit.
And the pistons will now stick out of the block. So you need to get `stroker' pistons with a shorter pin to crown height. Sometimes you can machine the piston top of stock pistons, if thick enough. Not always.
Whether a 1275S block or later 1275 block doesn't matter. They are pretty much the same deck height.
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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.