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| Re: A15 crank wil NOT fit in A12 block |
Subject: Re: A15 crank wil NOT fit in A12 block
by dattoboy_nz on 2019/9/10 19:59:58
Pics as promised. These are a 77mm Mahle forged piston out of a standard BMW Cooper S Mini that had run a big end.
The initial plan was to run a RB20 rod (121.5mm long same as a12) and had a 21mm small end same as the supercharged mini pistons. This plan failed when we hit the oil gallery clearancing the block because there was to much meat around the big end of the rod.
Plan B - use some late a12 rods. They have the same meat on the OD of the small end as an A12A rod (19mm pin) so they were opened up from 17.45mm to 21mm. Engine builder was plenty happy with opening them up to 21mm. The block then only needed minor clearancing for the rods. The crank itself spun in the block when doing a dummy up years ago.
Crank did need machining. Counterweights turned down slightly and flat spots added for clearance at BTC - see pics.
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