Need help identifying this 1275/1300 crank

[mnicoop63]

I recently aquired a couple engines. They are both Austin America automatic blocks and have 1275 aluminum tags on the back. One of them is still bolted to the trans and appears original as the paint matches on both eng/trans and everything is still attached except the bell housing and cover. I can see inside and it has a 1505A crankshaft. It's the second engine that I can't seem to find anything about the crankshaf. The engine was simply sitting on top of the transmission and is a different color than the transmission so I figure they didnt originally go together. I pulled the engine off the transmission and the crank was only held in by one main bearing cap and all the rod big end caps were off the rods. The 2 main caps and rod ends were in another box of parts. I disassembled the engine and the crankshaft has 2 inch mains and 1.625 big ends. The rods are AEG521 with AEG145 caps. It has a duplex timing chain AEA696 and AEA695. I can find information on those parts but I can't find anything about the crank. It's an EN16T crank with ESC5A on one side and on the other side the forging is pretty bad and I can't make out what it would have said. Also it appears that maybe another casting mark had been ground off and it looks like 393 was stamped in its place. To be honest its hard to make out the first number. It seems like it was stamped crooked. At some angles the first number looks like a 6 and at others a 3. I believe its a 3 but who knows. There are other letters stamped on the crank and I have included pictures. The crank looked hardened to me and I took it to my machinist and he confirmed that infact it is. He seems to think it is nitrided. Does anybody know anything about this crank? I have searched a lot and can't find anything about it. Everything is standard. It's never been turned and the thrust washers that were in the block are standard if that helps. I was thinking maybe it is a AEG623 but how can one confirm? The block is a 12H in the 5000 range. I was also wondering if maybe it came out of a 12G block but then again how can one confirm. Any help would be greatly appreciated as it is driving me crazy that I can't figure it out.

[Simon776]

A 1393 was the early crank from a 12G engine.

[Supersonic]

I’ve never seen a 12G automatic cylinder block. All were out of very early manual ADO16 Mk2 Riley Kestrel, MG or Vanden Plas 1300 cars. The 12G engine was not the S type block with tappet chest covers. These date from about July 1967 when the solid wall transverse block first appeared. These had engine number 12G, crankshaft number EN16T (12G1288) with 1.5/8 inch journals. It is important to remember that this EN16T crankshaft out of this solid wall engine has a different centre main bearing width to the Cooper S and earlier ADO16 1275 engine that both had tappet chest covers.

Hope this is of some help to you

Alan

[251 ENG]

All mk3 cooper s cranks will have 3 oil holes in each big end one of which will be blocked with a brass plug.
The main bearings will be cross drilled right through

[Supersonic]

All mk3 cooper s cranks will have 3 oil holes in each big end one of which will be blocked with a brass plug.
The main bearings will be cross drilled right through

Simon, the Mk3 Cooper S crankshaft is really good in my book. Used them in Autocross racing and never had a failure. In fact I've seen EN40B cranks broken but never a Mk3 crank

Alan

[mnicoop63]

A 1393 was the early crank from a 12G engine.

I haven't been able to find anything other than the 12G engines having the 1287/1288. I'm pretty sure that is ther number. I have read so many things lately about crankshafts my damn head is scrambled. There is a lot of information that seems to contradict other information. It gets confusing. I haven't seen anything about 1393 stamped on cranks anywhere. Do you know of anywhere I can read about it?

[mnicoop63]

I’ve never seen a 12G automatic cylinder block. All were out of very early manual ADO16 Mk2 Riley Kestrel, MG or Vanden Plas 1300 cars. The 12G engine was not the S type block with tappet chest covers. These date from about July 1967 when the solid wall transverse block first appeared. These had engine number 12G, crankshaft number EN16T (12G1288) with 1.5/8 inch journals. It is important to remember that this EN16T crankshaft out of this solid wall engine has a different centre main bearing width to the Cooper S and earlier ADO16 1275 engine that both had tappet chest covers.

Hope this is of some help to you

Alan

Alan the crankshaft, rods and pistons along with timing gear were in block 12H/185/H5114. Definitely an Austin America automatic block. The crank only had the front cap installed and none of the rod ends. The caps and ends were in a box. I have no idea if the crank was being installed or taken out. If it were being removed something must have been wrong because the pistons have very little wear and the rings still have ridges on them. I got it from a shop that the owner passed away. His son-in-law said the motors had been sitting for 15+ years. I thought maybe it was possible that it came out of the earlier 12G engine.

I am a little confused. The 12G1288 crankshaft was in a 12G solid wall block. It has different center main bearing width than the S. (I think I read the difference is the S is 1/32 narrower? Am I wrong that the actual bearings are the same but the block and cap are whats narrower on the S?) The 12G1288 is EN16T with 1 5/8 inch journals from a solid wall block. Is that considered a 1300 crank? Is it hardened? The really early AD016 1275 cars had an S bottom half, correct? and that's what you are referring to about the engine with tappet covers? What crankshaft is in that engine? For some reason I thought those were the 12G engines. There is a great thread on here that's about the S engine in early AD016 cars that is about 30 pages but it didn't mention anything to help me ID this crank.

[mnicoop63]

All mk3 cooper s cranks will have 3 oil holes in each big end one of which will be blocked with a brass plug.
The main bearings will be cross drilled right through

It is not cross drilled on either the rod journals or the mains.

[Gary Schulz]

All mk3 cooper s cranks will have 3 oil holes in each big end one of which will be blocked with a brass plug.
The main bearings will be cross drilled right through

Simon, the Mk3 Cooper S crankshaft is really good in my book. Used them in Autocross racing and never had a failure. In fact I've seen EN40B cranks broken but never a Mk3 crank

Alan

Was it common to have EN40 S cranks with cracks (maybe stress related)? I have 3 EN40 cranks that all came back with failures after magnetic inspection. Is it possible that the cracks they see are more just surface imperfections on the hard surface and that they are still usable after grinding and re-nitriding?

Don't mean to hijack the thread but it has me thinking that there must be a reason why I can't throw them out!

[Spider]

All mk3 cooper s cranks will have 3 oil holes in each big end one of which will be blocked with a brass plug.
The main bearings will be cross drilled right through

Simon, the Mk3 Cooper S crankshaft is really good in my book. Used them in Autocross racing and never had a failure. In fact I've seen EN40B cranks broken but never a Mk3 crank

Alan

Was it common to have EN40 S cranks with cracks (maybe stress related)? I have 3 EN40 cranks that all came back with failures after magnetic inspection. Is it possible that the cracks they see are more just surface imperfections on the hard surface and that they are still usable after grinding and re-nitriding?

Don't mean to hijack the thread but it has me thinking that there must be a reason why I can't throw them out!

The EN40B Nitrided Cranks because they are locally so hard on the journals and other machined surfaces are also brittle and so much more prone to cracking. I've seen way more broken S Cranks than any others.

[Supersonic]

Have to agree with Chris above, I've only ever seen EN40B nitrided crankshafts broken, never a 12G1817 broken. In answer to the question asked by mnicoop63 the Mk1 up-market ADO16, Vanden Plas, Riley Kestrel, Wolseley and MG 1100 with the 1275 unit used a complete Mk1 Cooper S thin wall block, EN40B nitrided crank and Cooper S rods. It used a MG Midget / Austin Healey Sprite cylinder head. The early solid wall 12G engine had a similar crank and used MG Midget / Healey Sprite rods and cylinder head.

Hope that is helpful

Alan

[Gary Schulz]

The EN40B Nitrided Cranks because they are locally so hard on the journals and other machined surfaces are also brittle and so much more prone to cracking. I've seen way more broken S Cranks than any others.

So is the failure at the surface where they are hardest or is it likely a deep metallurgical failure? Sounds like I may actually have to toss 3 Cooper S cranks then!

[Spider]

The EN40B Nitrided Cranks because they are locally so hard on the journals and other machined surfaces are also brittle and so much more prone to cracking. I've seen way more broken S Cranks than any others.

So is the failure at the surface where they are hardest or is it likely a deep metallurgical failure? Sounds like I may actually have to toss 3 Cooper S cranks then!

The failures I've seen do start at the surface, and usually from Harmonics and normal running Impulses. Some start around the radius and some from boundary where the raw forging finishes and a machine surface starts. The latter occur because the Nitriding doesn't penetrate the raw finish of the forging too well so instead of a nice 'tapered' boundary zone between the Hard and Soft areas, it's much more distinct and so the Nitrided zone usually crack right on that. Those that start on the radius have not been as a result of a poor radius, but from Harmonics. Off hand, every one of these that I've seen always breaks in the same place - adjacent the Centre Main Bearing on the No. 2 side.

[Gary Schulz]

The EN40B Nitrided Cranks because they are locally so hard on the journals and other machined surfaces are also brittle and so much more prone to cracking. I've seen way more broken S Cranks than any others.

So is the failure at the surface where they are hardest or is it likely a deep metallurgical failure? Sounds like I may actually have to toss 3 Cooper S cranks then!

The failures I've seen do start at the surface, and usually from Harmonics and normal running Impulses. Some start around the radius and some from boundary where the raw forging finishes and a machine surface starts. The latter occur because the Nitriding doesn't penetrate the raw finish of the forging too well so instead of a nice 'tapered' boundary zone between the Hard and Soft areas, it's much more distinct and so the Nitrided zone usually crack right on that. Those that start on the radius have not been as a result of a poor radius, but from Harmonics. Off hand, every one of these that I've seen always breaks in the same place - adjacent the Centre Main Bearing on the No. 2 side.

So is it worth grinding the journals to see if I can get down below the crack (it looks to be in the radius)? Seems like a poor compromise if many of these EN40 cranks suffered this same fate where the cheaper (less hard) alternates never have this issue. I have seen 1300 cranks machined to fit as an "S" replacement. Maybe this is a really good route to take. Should have started a separate thread on this!

[Spider]

Gary, I know it flies in the face of thinking in some quarters, but having found out the hard way, I haven't used a Nitrided crank for anything with moderate to serious output because of their brittleness.

Cranks see a lot of twisting and bending in any use.

Hopefully this will work here?



Nitriding was done for some competition stuff as it allowed the cranks to go for 2 or 3 builds without the need to a grind, but, they do suffer cracking.

You might be able to grind your cracks out. The only way to to out is grind and test them. Or X-ray them, but after paying for that, you may as well buy new cranks.

[Exminiman]

The EN40B Nitrided Cranks because they are locally so hard on the journals and other machined surfaces are also brittle and so much more prone to cracking. I've seen way more broken S Cranks than any others.

So is the failure at the surface where they are hardest or is it likely a deep metallurgical failure? Sounds like I may actually have to toss 3 Cooper S cranks then!

The failures I've seen do start at the surface, and usually from Harmonics and normal running Impulses. Some start around the radius and some from boundary where the raw forging finishes and a machine surface starts.

Vizard talks about this as well - recommends almost to insistence that radius should be smoothed out to avoid sharp edges - which makes sense to me, logically, cracks seem much more likely to start on a sharp edge. I wonder how many machined cranks actually get the radii smoothed out.

[Spider]

The failures I've seen do start at the surface, and usually from Harmonics and normal running Impulses. Some start around the radius and some from boundary where the raw forging finishes and a machine surface starts.

Vizard talks about this as well - recommends almost to insistence that radius should be smoothed out to avoid sharp edges - which makes sense to me, logically, cracks seem much more likely to start on a sharp edge. I wonder how many machined cranks actually get the radii smoothed out.

The first type of failure I've mentioned here, while in the region of the radius, they don't actually start in the radius itself, but eventually run through that way. They start on the outer edge of the web. While it is the crank that breaks, these have been from a failed or inappropriate Harmonic Damper. All the same, the Nitrided Cranks don't take this too well and if you look at the GIF I posted above you can see why, we have a bending and twisting motion in use and this is bigger at the outer edges than is at the journal radius, basically tearing them from the edge. Why these cranks don't stand up to it so well is the Nitriding is firstly, very very hard, but is only around 12 - 15 thousands deep, whilst hard, it does make it brittle. Then where the hardened case meets the raw forging, there's a fairly marked softer zone - a perfect place to start a tear.

Because these types of failures run through the Radius, it;s very easy to assume that's where they started.

These cranks would fair better if all the raw forged skin is removed from the crank before Nitriding, but. in doing so, when Nitrided, it will relieve and bend more than they usually would.

[snoopy64]

Ok, so as long as we are talking nitrided and not tufftrided then the reason any rotating component is nitrided is to increase its fatigue performance and surface wear..however the nitrided surface traditionally is made up of 2 layers (with modern equipment this can be avoided). The top layer is extremely hard and brittle and prone to cracking, this layer should be polished/ground off. The improvement in fatigue performance comes from the compressive stress induced in the surface as a result of a volume change caused by the nitriding...shot peening has the same effect.

[1071bob]

I posted this cracked crank picture ten years ago, might be of interest to the current discussion. It's a 1275 S EN40 crank under the UV lamp.

[Gary Schulz]

Here are two of my unfortunate EN40 cranks. If it is in the nitrided top layer can they be reground and re-nitrided? I guess there is no way to tell until you grind them down first...