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I have a crankshaft with markings from what I can see are. :AEG 479: Would this be a :S: crank.?The rods bolted to it are 521 . All of the :S: cranks I've had in the past have had :EN40 : on them but there is no sign of this .... Ken

Going by my crank chart it is. AEG 479 / 480 = EN40B cross drilled & nitrided. 1.625" journal for the con rods.

If its got AEG 479 stamped on it in small type it will be an AEG 316 forging but machined in to an AEG 480 crossdrilled spec. crank by the factory . They normally grind the AEG 316 off .

Later S Cranks weren't EN40B nor Nitrided. Off hand I can't recall when they were dropped.

Spider wrote:Later S Cranks weren't EN40B nor Nitrided. Off hand I can't recall when they were dropped.

They went over to the cheaper EN16T, the T standing for Tuftriding..........

Ah excellent . Thanks for information

Smiffy wrote:

Spider wrote:Later S Cranks weren't EN40B nor Nitrided. Off hand I can't recall when they were dropped.

They went over to the cheaper EN16T, the T standing for Tuftriding..........

According to Special Tuning, that was also the standard 1300GT crank. (They also insisted it was perfectly OK for all rallying and anything outside of racing and "would take 12:1").
If you ordered a new S crank or half engine in early 71, that's what you got.

LMM76C wrote:

Smiffy wrote:

Spider wrote:Later S Cranks weren't EN40B nor Nitrided. Off hand I can't recall when they were dropped.

They went over to the cheaper EN16T, the T standing for Tuftriding..........

According to Special Tuning, that was also the standard 1300GT crank. (They also insisted it was perfectly OK for all rallying and anything outside of racing and "would take 12:1").
If you ordered a new S crank or half engine in early 71, that's what you got.

I'm pretty sure the standard 1300GT Crank and those fitted to the 1275 GT while EN16T were not Tuftrided. It is quite likely that by 71 if a crank was ordered, that would have been the case, however there was an AEG623 which was in EN16T and was Tuftrided, these were fitted to the Cooper S from somewhere in 68 - 69 I think. The very last of the Cooper S Cranks (I think commonly referred to as MKIII Cranks), were not Treated at all, these were 12G1505.

The 1300GT / 1275 GT Small Journal Cranks were 12G1287, 12G 1288.

12G1505 crank was EN16 and had a 1.75" big end journal. So wasn't fitted to any S engines........

Ha, my bad, yes, the 12G1505's weren't fitted to S's.

BTW, the 'T' in EN16T means it's been Tempered. Nothing to do with Tuftriding.

This is something I've often wondered about. If en16t base material is tampered, any hardening would be removed in the process of making the crank. Re-heating and hundred tonne steam hammers tend to do that, so there would be absolutely no point in using en16t over en16. Tuftriding is applied to a nearly finished crank that only has final polishing to size of the bearing faces left to do.