Can someone tell me the difference between these cranks and if they are interchangable???

Can the A+ be modded to go in and 1100s block with the 1100s rods??

Minimad

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You can take the boy out of the racer.........but not the racer out of the boy!

only physical difference is the A+ one has rolled fillet radii.
It bolts straight in an 1100S block, with any big journal rods including 1100S `lumpy' ones.

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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.

It all depends...

1100s motors had a 'small journal' crank or a 'large journal' crank - referring to the big end journal size (1 5/8 - small 1 3/4 - large)

The A+ cranks I believe are all 1 3/4 but I could be wrong.

Something worth considering if you have the small journal 1100s and you're dropping in the large journal A+ is that you can offset grind the large journal to increase your stroke approx 1/8 of an inch Offset grind the crank, take a few thou off each side of the rods so they fit the new crank, machine half the increase in stroke off the top of your pistons so they don't stick out the top and then make sure your compression ratio isn't too high

He's comparing a large journal 1100S crank with a 1275A+ crank (see title).
Both are large journal (1-3/4" crankpins).

Offset grinding a crank that has rolled fillet radii is not a great idea really, but has been done.

,edit> reason it's not a great idea (IMO) is you finish up with a normal ground fillet 1/2 way round the crankpin and a hollow `rolled fillet radius' for the rest.
The term `stress raiser' comes to my mind.....

<edit 2> here's my 12G1505, 84.33mm stroker crank, after wedging and before final linishing... journal sizes std/std.

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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.

fair enough... I'll read more closely next time...

Thanks Guys

As you can probably guess from the multiple different threads.. I am considering either replacing the crank ( a 12G1505) with an A+ crank as the tail has quite bad rust pitting.

I know this is a large journal crank, but is the A+ cranks good for a few revs??? This would be to put in my 'race' motor
Motor is currently running
full steel main caps
Lightened flywheel
lighted and balanced rods with hypatec pistons +.20 (and it's an auto block!)
Kent MD296

Minimad

Ps No stroker motors here...not allowed in historic racing

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You can take the boy out of the racer.........but not the racer out of the boy!

Graham Russell is building my A+.

40thou over.
A+ block
A+ gearbox with Tran-X diff.
Lightened fly
Straight cut drop gears
A+ head with extensive work
A+ crank, wedged and going to be 'tricked up' a bit
A+ conrods, which will be attended to in the weight department.

All the other usual bits, Weber etc etc.
Hopefully should see 120 @ the fly all going well.

I had the choice to go a Small journal, and stroker, but decided that I had already bought enough bits to build up the big J, so I did.

The A+ cranks aren't old and abused, as some small J cranks, so this is a thing to consider.
All of the Mini Seven racers use these, and don't have issues so I that's good enough for me


edit: You entering in Nc class?

Yes Nc racing.

Haven't got there yet... still "practising" in the regularity Can't see myself graduating any time soon!!

Minimad

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You can take the boy out of the racer.........but not the racer out of the boy!

At least you're out there having a go!

I'm still yet to get out there

Mind throwing up some pics of the Mini?

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You can take the boy out of the racer.........but not the racer out of the boy!

MiniSport UK has A+ cranks on special for £175 I think, with bearings.
But it will cost you heaps in freight etc, as my mate Dave Gray (Nb Cooper S) found out.

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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.

Lets try and fix the old one first me thinks........might be cheaper too

Minimad

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You can take the boy out of the racer.........but not the racer out of the boy!

Fwoor that looks very nice!

Hi Minimad,

I've just taken out an A+ Crankshaft out of my race motor.

It ran for around 15 meetings before it cracked! Some are good, others not so good.

I broke the end off the previous one second time out!

HRS

PS: Great looking race car!

nice looking car