35 replies to this topic

[JVA10L]

Why would BL mess about putting an EN16T Mk 3 1275S crank in a 1300 block when they were still building S engines in S blocks? The Mk 3 S crank and 1300 GT crank were made from the same forging.

It's a long time ago, but as far as I remember all Mk3 'S' engines had the solid block, the EN16T crank, S rods and a 12G940 11 stud head with slightly bigger inlet valves (head stamped 12G1805). The 1300GT had the 12G1805 head and the crank was the same casting but the 'S' crank was tuftrided and the GT not. The 'S' had the non-vacuum distributor. The 'S' G/B was remote change and had hardy-spicer couplings but the 1300GT had the sandwitch plate remote, not sure about the couplings.

The Mk3 'S' engine proved to be almost bullet proof with the combination of the solid block and tuftrided EN16T crank good for 8000rpm and the 12G1805 head being more reliable than the original 'S' head.

So for the OP, what you have there is the basis for a really good engine. The crank has the larger big end journals which suggests it is from an Allegro and not a 1300GT so it is not tuftrided but it will still be a very strong engine.

Edited by JVA10L, 17 April 2013 - 09:11 AM.

[govig]

Just reading through these posts to try to establish the key differences in a 1300GT engine.

 

I have an alleged 1300GT motor sat in the workshop that I might do something with if it is a genuine 1300GT. The ID plate is long gone and I measured the bores (which look good) that work out at 1310cc. Does anyone have a list of what to check for to properly establish if this is a 1300GT motor?

[tiger99]

I seem to recall that one significant difference is that the "S" had a nitride hardened crank, which lasts a very long time, while the 1275GT and 1300 did not. Feel free to correct me if that is incorrect, for example due to production rationalisation.

[carbon]

1300GT has a tuftrided crank, which has different part number stamped on it.

[Spider]

1300GT has a tuftrided crank, which has different part number stamped on it.

 

I actually just went looking through some factory info on this as I was of similar thought, but no.

 

The crankshaft ID (as per factory advice) is stamped in to the 5th Web of the Crank, though I know from my own experience, this can be very hard to find and sometimes not there.

 

The interesting bit is, that (at least up to the CAM6232 &CAM6581 (part nos) which I don't have definite info on) if the 1275 Crank were made in EN16T, they were ALL Tuffrided and the few that were done in EN40B, were of course Nitrided. I was of the mind prior to checking on this that only some were treated, but there you go.

 

They go on to say if hardening facilities are not available, those stamped (on the 5th web) 12G956 should not be re-ground. All others can only be reground maximum 0.010". If hardening facilities are available, then all cranks can be re-ground, to a maximum 0.040".

 

While the small bore engines used a EN16T crank, these seemed to be untreated.

 

<EDIT: While well OT, this does also raise a further dark cloud over the current replacement bronze bushes being supplied for our primary gears. >

 

Here's one factory document, from the 1100 series in fact, on the cranks;-

 

 

I have another which I'll post up. It's similar to this but goes a bit further.

Edited by Moke Spider, 05 June 2016 - 12:36 AM.

[Spitz]

"Only Cooper 'S' with 9F prefix engines had EN40B forged steel nitrided crankshafts. All other A series used EN16 material which was only tuftrided on MK3 'S' and 1300GT (ADO16) with 12G1683 stamping number on crank"

 

(from minispares)