would need conrods that dont have the protusion on the rod bolt top area of the mains
eg.
http://4.bp.blogspot.com/-U5bKqqgO97E ... /s1600/connecting+rod.gif

will be interesting to see what you think of the bigger fatter torque area under the curve
eg. driveability etc. as Im sure no matter the head work, its going to have some serious
gas velocities with response normal long rod engines wont be able to match.

See the minor scallops in the photo of the underside of the block? Those chamfers had to be a lot larger for the RB rods and broke through into the oil gallery. Unsure if a aftermarket RB rod would help or hinder. Would have to buy one or a set to see how they compare?

Can you reveal where on the rods and block hit the block or pistons?

Would spool rb rods do the trick or worse problem?
as I sometimes find a set of 5 on yahoo auctions.

Im still interested in doing a sleeved 79mm version for the mazda head
conversion on an A12 block oneday as the better flowing head will make
full use of the faster velocities of the rod stroke ratio.

No problems Rallytwit. I have probably got a little carried away but I'm excited to see how it all goes!

Thanks for posting the information and photos; I guess the title should read "will not fit without modification"

Very cool build.

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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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oh to hear someone going the road less travelled!!!!
pure delight! bushed piston pin bores?

for those interested in a little history of the new Mini engine

Quote:


For the chev 400 it has 105mm size pistons while the datsun 77mm in this case
95mm stroke vs 82mm stroke. I wonder if there is a formula to calculate how
much force there is on the side walls with the changing diameters and strokes.

The short stroke ratios usually make use of massive port heads as usually
found in multivalve engines today. However I also wonder how much better this
ratio would be for spooling a small turbo so there is zero lag.

Ive been wondering how these late 1.4-1.5 vw and bmw turbo engines are making
v8 type torque and v6 type power with no lag at all. Driving a 1.4 vw we had
50mpg crazy power everywhere yet no visible lag. Can this be done with an A12
with that capacity, it would be very sweet. The short ratio creates supersonic
speeds that favor boost or race engines as mentioned.

I seem to recall the Mini has 21mm pin but yes the pin height is 26.5.

Was the A15 crank modified at all?

Were the Mini pistons OEM/replacements or from someone like JE, Wiseco, Wossner etc?