In one of my recent old racer interviews I got told that he had the 1071cc engine converted to a 970 by swapping the crankshaft for a shorter stroke one, back in 1964ish. This was because with the 1071 you would have to compete in the Grp 2 1300 class, which obviously was disadvantageous. .
My questions:
would that be possible with reasonable effort?
what crank would that have been?
what else needed changing to do so?
Was this something feasible back in the day?
It is a fact that 970S engines were hard to get by here in Austria, so the motive makes sense.
I just would like to know more so not to spread utter bollox.
Thanks guys.
How to convert a 1071S engine to below 1000cc?
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MiNiKiN
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How to convert a 1071S engine to below 1000cc?
Yes I am a nerd: I am researching the Austrian Mini-racing scene of the 60s and 70s 
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Rusty old S
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Re: How to convert a 1071S engine to below 1000cc?
Same cylinder bock 1071/970 same cc.s in the head, change to a 970 short stroke crank , 970 con rods slightly longer, flat top pistons to adjust the compression ratio, or reduce combustion camber in head by skimming. Easy. Oh remove 1071 tag.
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MiNiKiN
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Re: How to convert a 1071S engine to below 1000cc?
Thanks! Sounds as if the story I have been told is coherent.Rusty old S wrote: ↑Sun Feb 04, 2024 7:10 pm Same cylinder bock 1071/970 same cc.s in the head, change to a 970 short stroke crank , 970 con rods slightly longer, flat top pistons to adjust the compression ratio, or reduce combustion camber in head by skimming. Easy. Oh remove 1071 tag.
BTW: said chap was a friend of Jochen Rindt, Helmut Marko and Niki Lauda and kindly provided me with a few stories from back then when they were out and about before they got really famous. I love to listen to those old stories
Teaser: attending Gaisberg hillclimb he tried to do some espionage on what kind of anti roll bar Warwick Banks was using on his Cooper. Got caught red handed by the man himself and shewed away.
Yes I am a nerd: I am researching the Austrian Mini-racing scene of the 60s and 70s
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CooperTune
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Re: How to convert a 1071S engine to below 1000cc?
I have had a 970 crank for at least 20 years. I have been on the hunt for rods just as long. I have two 1071s, and looking at buying three more if he will make up his mind. I do have a set of six-inch rods, which I plan to use with std S block and 1071 crank. Of course, I could machine .125 off a block and run the 970 crank. Steve (CTR)