hey all. i have this 1275 crank that i am not sure what it is. it has AEG???FORGED into the webs of it but the numbers are ground off so i cant make out the three digits that follow it. it also has 12G1288 Stamped over the top of where the above AEG code has been ground away. i know 12g1288 is a small journal 1100s crank but this crank appears to be tuftrided ( i can file the webs as they are very hard) which makes me wonder if it is an s crank? i am wishing to list it on ebay and just want to get my facts correct. thanks.

Yes it's probably an early 1100S one.
All the small journal 1100S cranks I've ever checked were tuftrided.
They are less likely to crack these days in race motors than the old and now brittle S EN40B ones.

To fit it to an S block you would need +.030" thrust washers- these are NLA from UK but are still made here by ACL.
I got some from Lindsay Siebler, www.minis.com.au

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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.

thanks. i thought this was the case. so its a good crank for high powered motor? is there any negatives to this crank? what would someone expect to pay for one these days? sorry about all the questions

Yes it's a good crank for a high powered motor.
Early ones were crossdrilled, the later ones not, but they are both good.

Only negative is you can't stroke it like the big journal ones (but they are all soft, so meh).

What it's worth depends on its size- a good std/std one these days would probably bring $350+ from a racer, IMO.

Get it crack tested before sale, or sell it subject to testing.

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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.

Marcello,
I have an early 1100s cross drilled crank in my motor and GR said they are the ones he prefered in all of his race engines, so yes as Kev said they are great for high power motors.

cheers Gerg

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May the fork be with you.

thanks guys for the help. i have been thinking about selling it to get a en40 crank but i guess as this one is approved by GR then it may just go into my 1275. good o!

Just remember the tufftriding process doesn't go very deep. If the bearing journals are ground well undersize they will get soft.

On an S EN40B crank, the nitriding is deeper- some say .040" or more. It's a mystery how they got the depth they did, as most nitriding these days is only good for .010". It's a lost art apparently.

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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.

its standard on the big ends and 10 under under on the mains. it needs a regrind on both though. will it be okay?

Sure.

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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.

Hey Doc, Is there any way to tell if the nitriding is still good on an S crank? I have a 1071 S crank freshly ground to 0.020" under on the main journals, was hoping it would still be treated, but how to tell?

(sorry for the hijack, I too have heard from trusted mini mechanics and racers the 1100S S/J cranks are one of THE best 1275 cranks, tuftrided, and bloody good in general!)

Matt

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68 Deluxe.... it's shiny..... I like shiny!!

The time to tell if it's still hard is when it's being ground, it is obvious to the dude working the grinding machine. The spark pattern and grinding sound are different.
You can't really do a Rockwell etc test on a journal which is going to have bearings running on it there- an exception is maybe the centre of the main journals (if you are using pre-A+ bearings with the groove).

There is one place left in Melbourne which does tuftriding- for the aero industry, most of the others in Oz have stopped the process due to environmental and health concerns.
No, sorry I don't know the name of the place... try a Google search.

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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.