XPAG Crankshaft

[Bob Grunau]

I am re-building the original engine for my 1952 MG TD and have a choice of two new crankshafts, one new in the BMC box NOS 168557 BMC crank that I have had since about 1970. The second a recent new Moss crank, p/n 451-490, 4340 forged chromemoly steel.
I have several questions.
1-Any suggestions as to which crank is better for a- street use? b- race use ?
2-Will both cranks be OK to low penetration weld up the seal scroll area to install the Chevy split seal?
3-Will both cranks benefit from Tufftriding or is that not recommended for the Moss crank?

Thanks for any information.

Regards, Bob Grunau

[Chip Old]

Hi Bob,

Depends on what "street use" means to you. The last time I saw you drive a T-Type on the street was probably 20 years ago, and the details have leaked out of my brain. If you're a relatively sedate driver who doesn't put a lot of mileage on the car, the NOS crank should do fine.

We know the NOS crank can be welded at the scroll (lots of recent discussion about that here), and I know it can be Tufftrided (but not nitrided). I suspect Moss' 4340 crank can also be welded, and I'm pretty sure it can be nitrided (which might be a better choice than Tufftriding). You should probably try to get advice and more detailed specs from Moss on that.
--
Chip Old 1948 M.G. TC TC6710 XPAG7430 NEMGTR #2271
Cub Hill, Maryland 1962 Triumph TR4 CT3154LO CT3479E
fold@bcpl.net

[Peter Dubaldi]

Greetings,
Along this thread, are there recommendations for a competent shop that can tufftride crankshafts, preferably in California?
Thanks-
Peter Dubaldi
TC 3780
Eureka CA

[Skip Kelsey]

Bob:

The new Moss crank should be used for all applications. To my knowledge, no one has broken one yet. The factory crank is just waiting to break. Also, the Moss crank is already nitrided. It should weld up very nicely for the rear main conversion.

Cheers:

Skip Kelsey................................

[Chip Old]

Peter, your reply was directly to me but I'm replying to both T-Type lists
instead of just to you. Hope you don't mind, but the whole point of
Internet mailing lists is to share information with a group, and this is a
thread others seem to be interested in.

On Fri, 23 Jun 2000, Peter Pleitner wrote to Chip Old:

> I agree with Chip on all opinions except one, that being the negative
> on Nitride hardening of an XPAG crank. I had mine Nitride hardened
> and balanced, and have put over 7K miles of hard use on it. And my
> oil pressure is still at the upper limit of comfort, e.g. 90 psi when
> cold, and no less than 65 psi otherwise.

There were two different factory crankshafts, the primary difference being
that the later ones (from late TD production on) were forged from a more
durable grade of steel. However, according to the Nitriding experts of 25
years ago (last time I looked into it) neither grade of steel is suitable
for Nitriding. I don't remember all the details (sorry, another brain
leak), but as I recall Nitriding makes original XPAG/XPEG cranks very
brittle. In practical terms, this means a Nitrided original crank will
resist wear far better than an untreated crank, but will be far more
likely to break.

> I've heard of surface crazing twice due to Tufftriding, but this on
> 1950s vintage Alfa cranks. This was traced the first time to a cold
> winter draft on a hot crank, and the second time due to Nitriding a
> previously Tufftrided crank.

I know that can happen, but I don't know what conditions cause it. A
Tufftrided crank should always be micropolished anyway, because
Tufftriding leave a slightly rough surface. That removes the crazing if
not too deep, but if not you have to regrind and re-Tufftride.

> On a related expensive and labor intensive subject, I've concluded
> that a possible cause for rebuilt crank failure which I've recently
> become aware of is incompetent dressing of the grind stone at the
> crank grinder. In the past several years I've learned of a rash
> inexplicable crank failures traced to an extreme reduction in the
> radius between the bearing surface and the throws of the crank. A
> narrow, or worst of all, sharp edge at either end of the bearing
> surface creates stress risers and should retire the crank to door stop
> duty. I wonder if this rebuilt condition could not explain some of
> our reported XPAG crank failures. How many on this list have seen an
> XPAG crank break at either end of a bearing surface?

Yes, reduction of the radius at the edges of the journals by incompetant
machinists does increase the risk of breakage, and is a common problem.
Choose your machinist with care, and make sure he understands that the
radius must be maintained on all journals. In fact, if your machinist is
willing, have him measure the *installed* main and rod bearings, including
width from radius to radius as well as inside diameter, and grind the
journals to suit. It is sometimes possible to grind the journals with a
greater than standard radius, which increases crank strength.

However, incorrect grinding isn't the only cause of breakage. Even brand
new unground XPAG/XPEG cranks were known to break. It just isn't a very
strong design to begin with.

--
Chip Old 1948 M.G. TC TC6710 XPAG7430 NEMGTR #2271
Cub Hill, Maryland 1962 Triumph TR4 CT3154LO CT3479E
fold@bcpl.net

[Awini Ambuj Shanker]

and I know it can be Tufftrided (but not nitrided). I suspect Moss' 4340 crank can also be welded, and I'm pretty sure it can be nitrided (which might be a better choice than Tufftriding).

What's the difference between the two?and can anyone explain the processes to me in layman's language,
thanks
regards
Awini Ambuj Shanker
TC 0365

[PADDY WILLMER]

Gentlepeople

The 168557 crank, once tuftrided, is ok for all applications. Get it balanced, along with all the rest, and you will avoid the critical harmonic that causes these cranks to break if taken over 5,800 rpm. Mine has been in many a year and goes safely to 7000 rpm.

The TF1500 had a nitrided crank with lead-indium bearings. If they were reground they had to be re-nitided, or otherwise fitted with white metal shells. In the olden days people didn`t realise this and re-fitted the lead-indium shells, which promptly failed!

In the UK the cheque book racers use a new Phoenix forged steel crank. Thes are virtually unbustable and will rev to 8000 and over. The limiting factor is the valve gear.

My 168557 has been tuftrided.

Hope this helps.

Paddy.

Racing TA/TC 0448 and Roadgoing TB 0594 [ also with balanced and tuftrided 168557].

Derbyshire. UK.

[ROGER FURNEAUX]

Skip Kelsey wrote:
The new Moss crank should be used for all applications. To my knowledge, no one has broken one yet. The factory crank is just waiting to break. Also, the Moss crank is already nitrided. It should weld up very nicely for the rear main conversion.

There are two XPAG cranks, early one is p/n 168628, and the later TD type with alledgedly much better steel is p/n 168557, so which one is Skip referring to?

I think, speaking from memory, that the later one is EN40 steel, but we need a metallurgist (or Chip Old?) to confirm this and remind us of the difference betwwen Tuffriding & Nitriding and which steels can be treated.

Roger Furneaux (with one old spare undersize 168557 - cannot afford a new one!)

[Chip Old]

On Fri, 23 Jun 2000, PADDY WILLMER wrote to T-ABCs forever:

The TF1500 had a nitrided crank with lead-indium bearings. If they were reground they had to be re-nitided, or otherwise fitted with white metal shells. In the olden days people didn`t realise this and re-fitted the lead-indium shells, which promptly failed!

Don't think so, Paddy. I don't recall any factory parts list showing anything other than the same 168557 crankshaft introduced late in TD production. It is a stronger steel (EN40 if I remember correctly) than the TB/TC/early TD crank (168628), but is not nitrided.

Some factory parts lists show lead-indium bearings, but in the "Special Equipment" sdection, not as a production line part. They were also available from Vandervell and other aftermarket suppliers. The bearings themselves will take much more punishment than the standard white metal bearings, but will wear out an unhardened crank much faster. Tufftriding the 168628 or 168557 crank is recommended if lead-indium bearings are used.

In the UK the cheque book racers use a new Phoenix forged steel crank. Thes are virtually unbustable and will rev to 8000 and over. The limiting factor is the valve gear.

How much do the checkbook racers pay for a Phoenix crank? The Moss Motors crank also has a reputation of being unbreakable. I wonder if they are really made by the same foundary. Anyone here know? What's the price for a Moss crank these days? I don't have a current Moss Motors price list.
--
Chip Old 1948 M.G. TC TC6710 XPAG7430 NEMGTR #2271
Cub Hill, Maryland 1962 Triumph TR4 CT3154LO CT3479E
fold@bcpl.net

[Chip Old]

On Sat, 24 Jun 2000, Roger Furneaux wrote to T-ABCs:
There are two XPAG cranks, early one is p/n 168628, and the later TD type with alledgedly much better steel is p/n 168557, so which one is Skip referring to?

Either factory crank can break, but in theory the 168557 is less likely to break than 168628.

I think, speaking from memory, that the later one is EN40 steel, but we need a metallurgist (or Chip Old?) to confirm this and remind us of the difference betwwen Tuffriding & Nitriding and which steels can be treated.

Yes, I think you're correct that 168557 is made of EN40.

My old engineering references are packed away in the attic, so I'm working from memory here. Nitriding and Tufftriding both harden the surface, but two entirely different processes are used.

Nitriding produces a much deeper hardening, so a nitrided crank can often be reground once or twice without going into the softer core. If I remember correctly almost any steel alloy can be nitrided, but some tend to become very brittle as a result of the process. In the case of a crankshaft brittleness causes breakage, so you don't want to nitride a crank made of an alloy that will turn brittle. The alloys used in the original 168628 and 168557 cranks fall into that category.

Tufftriding is a patented process that produces a much shallower surface hardness, leaving the core of the crank unaffected. This makes it suitable for cranks made of alloys not suitable for nitriding (like the 168628 and 168557). A single regrind will eliminate the hardened layer, so re-Tufftriding is necessary after every regrind.
--
Chip Old 1948 M.G. TC TC6710 XPAG7430 NEMGTR #2271
Cub Hill, Maryland 1962 Triumph TR4 CT3154LO CT3479E
fold@bcpl.net

[Skip Kelsey]

Roger:

The XPAG crank that I refer to is the later improved crank. I had one in my engine for several years, having bought it new from British Motors in Berkeley Ca. After several years of driving, I tore the engine down for a rebuild, a Magnafluxed the crank. It was cracked in "Three" different places. This was the EN40 "improved" crank.

I have had the same experience with several other engines that I have rebuilt over the years. I am very happy with the Moss 4340 cranks. I do admit that I no longer do 7000 revs., but I still like to drive rather spiritedly. I also agree, that the "Phoenix" billet cranks are very good. They are also available with special full floating pins, and set up so that one can use MGB bearings, which can still be obtained in tri metal bearing material.

Cheers:

Skip Kelsey...........................

[Austin R. Baer]

Suggestion to all that have questions about heat treatment: Go to www.nass.org.uk and click on "GLOSSARY" to find short definitions of hundreds of commonly used terms (including Tuftriding and Nitriding) in the metals industry. The "bible" of the engineering world is the Metals Handbook, published by ASM (American Society for Materials, formerly the American Society for Metals). You can get an idea of the extent of their publications and activities at www.asminternational.org

Austin

[John T. Seim]

Chip Old wrote:
Don't think so, Paddy. I don't recall any factory parts list showing anything other than the same 168557 crankshaft introduced late in TD production. It is a stronger steel (EN40 if I remember correctly) than the TB/TC/early TD crank (168628), but is not nitrided.

With all of this talk about the 168557 crankshaft being stronger than the 168628 crankshaft, are the part numbers stamped on the crank? I just pulled out a used crank from the garage, and it has "22528" stamped on it, as well as "ESC M19". What crankshaft do I have?
John Seim
TC 6590
Irvine, CA

[Zissel-Kreuztal@t-online.de]

I am re-building the original engine for my 1952 MG TD and have a choice of two new crankshafts, one new in the BMC box NOS 168557 BMC crank that I have had since about 1970. The second a recent new Moss crank, p/n 451-490, 4340 forged chromemoly steel.
I have several questions.
1-Any suggestions as to which crank is better for a- street use? b- race use ?
2-Will both cranks be OK to low penetration weld up the seal scroll area to install the Chevy split seal?
3-Will both cranks benefit from Tufftriding or is that not recommended for the Moss crank?

Thanks for any information.

Regards, Bob Grunau

Hi Bob!
Exept for the early XPAG Crankshaft (breakage) will all the following Cranks work. The difference between a good or bad crank makes the final work: A good balancing of all moving parts would be more steady than only a re-sleeved Crank. Hardening or nitrate is not a must, but reduced frictional loss und wear.

Welding cause bending and changing in metall structure. Only work for specialists with ovens for glowing after welding! Why welding? There are very good working seal-conversions from Bob Schapel/Australia available! Harry Pyle could help you. He have fitted it, and his engine was dry after his "around the world" tour. It is mutch better than the moss sealing kit.

#3: Don't know: what is tufftriding? Is it kind of soft sandblasting without sand to polish the surface of the crank?

Greetings
Lothar Zissel, TC3762

[DickShaler@aol.com]

My experience with the Moss crank was mixed. The finish and balance was excellent right out of the box. However #4 rod journal had almost no side clearance and completely lacked a radius at the rear bearing surface -- Perhaps the machinist went to lunch and didn't mark his place. The flywheel flange was canted 8 degrees from the centerline of the crank -- easy to see if you really looked but not the sort of thing you want to find out after bolting up the flywheel.

After a few hundred dollars of proper machine and re-balancing work it came out fine.

Perhaps the Phoenix crank would have been a better choice given the time and expense of redoing the piece..

In another engine I broke three cranks over a period of years before finally going with the late factory model. There was not been a problem in many many miles. BTW all of the breaks occurred just aft of #1 rod bearing. I have heard this is the most likely failure location. Does anybody know if this is so.

Regards Dick

[Alan Moote]

How much do the checkbook racers pay for a Phoenix crank? The Moss Motors crank also has a reputation of being unbreakable. I wonder if they are really made by the same foundary. Anyone here know? What's the price for a Moss crank these days? I don't have a current Moss Motors price list.
--
Chip Old 1948 M.G. TC TC6710 XPAG7430 NEMGTR #2271
Cub Hill, Maryland 1962 Triumph TR4 CT3154LO CT3479E
fold@bcpl.net

Hi Chip,
The latest, 04/10/00, Moss catalogue list the crank as:

451-490 $1,795.00 CRANKSHAFT, forged in 4340 Chrome-moly-steel

Regards,
Alan Moote
Oceanside, CA

[taterry@aol.com]

how much do the checkbook racers pay for a phoenix crank?

Phoenix has a web site with prices...they list a TF crank at 1000 ukp or about $1500 at todays exchange rate...a hundred for shippng and they are less than Moss..............I'd bet Moss gets theirs from Phoenix...
Terry

[Harry Pyle]

All,

I have only ever seen them break at Number 1 rod journal AND number 4.

Regards Harry.

My experience with the Moss crank was mixed. The finish and balance was excellent right out of the box. However #4 rod journal had almost no side clearance and completely lacked a radius at the rear bearing surface -- Perhaps the machinist went to lunch and didn't mark his place. The flywheel flange was canted 8 degrees from the centerline of the crank -- easy to see if you really looked but not the sort of thing you want to find out after bolting up the flywheel.

After a few hundred dollars of proper machine and re-balancing work it came out fine.

Perhaps the Phoenix crank would have been a better choice given the time and expense of redoing the piece..

In another engine I broke three cranks over a period of years before finally going with the late factory model. There was not been a problem in many many miles. BTW all of the breaks occurred just aft of #1 rod bearing. I have heard this is the most likely failure location. Does anybody know if this is so.

Regards Dick

[Skip Kelsey]

Terry:

Moss gets the forgings made in England, but not from Phoenix.I sell the Moss crank for $1525.00.

Skip........................

[Bob Grunau]

I agree, have had one break at #1 and managed to drive it home slowly as the whole thing stayed together while I drove about 7 or 8 miles. The break was just crooked enough to drive the cam. Dropped the pan and everything looked OK till I rotated the crank and saw a bit of relative movement between the front web and the rear of the crank. Several others were cracked at #1 when magnafluxed and one at #4.
Bob

I have only ever seen them break at Number 1 rod journal AND number 4.
Regards Harry.