Crankshaft repairs / metal buildup

Hi all -

Not a 40 question but someone on here might have the know how or 'know a man that can' (or woman!)..

I've got a Maserati 3200GT motor in for works that has a knackered thrust bearing on the crank rear. Basically they have poor oiling as standard on the manual cars and the thrust bearings are prone to failure. This has happened on this motor and the crank now has a surface that has a ridge on it where the bearing failed, spun and wore the crank badly (0.034").

According to Maserati, the cranks cannot be reground and NO replacement bearings or shells are available other than 'std'..

SO, looking at a new crank really BUT someone has suggested it might be possible to metal-spray the surface, presumably building it up and then re-machine it to standard size and still be possibly cheaper than a replacement crank.

Anyone have experience of such processes or have had similar work undertaken? Can anyone reccommend a vendor?

I assume its steel & nitrided, & after the process of grinding the thrust/brg surfaces that the crank would have to be re-nitrided to restore journal hardness, which in turn will probably cause the crank to bend when any stress's induced by the brg failure are released. When you consider the implication of those possibilities and the downstream effects they can have its usually more prudent to buy a new crank. However if its made from no longer obtainium then you just take your chances.

we used to have shafts metal sprayed at a food factory back when i was serving my time, the problem with it is unless its done correctly it can flake off.

that and i have no idea if it could withstand the pressures in an engine. have you tried phoning a few local machine shops and see what they think?

Hi Paul,

Some decades ago my father used to work for a company called Metco, then in Chobham, Surrey. From a quick google it seems they are now Sulzer Metco; UK office in Newport, Gwent. Tel: 01633 600970.

Sulzer Metco - Thermal Spray

I'm sure they can recommend a workshop local to you - in my Dad's day this process was relatively low cost and so quite commonplace in small engineering workshops.

Best wishes,

Jim

Thanks guys, I'll lookup the Sulzer Metco link but on further inspection I suspect the crank is beyond recovery...:thumbsdown:

I'll call them and ask opinion though just in case.

I dread to think what a replacement crank from Masser costs...:shocked:

Totally agree with Jac the Mac on this issue -- a new crank would be the wisest move in the long run.
Any repair treatments to a crankshaft will only induce further problems

Don't know why but I missed Jac Mac's reply earlier..

Think a replacement is definately more sensible option now unless as you say, they are 'unobtanium'.

Before all else, get it crack tested ( Peter Knight will do it ) as its most likely a spiders web you cant see ! Frank

Paul
I worked for a while at a repair shp where we did a lot of diesel engines. We regularly sent crankshafts out to be brought back up to standard spec. These were engines with typically 400,000 to 500,000 miles on them.
The process was a submerged arc buildup an the journals, a complete re-grind and polish, and re hardening. I remember it being a nice looking job, and they fit well with correct tolerances. Most of these engines ran another 400,000 or so or until the chassis and cab were no longer viable for repair.
Of course in the 70s and 80s these crankshafts were $3,500.00 so it was cost effective, as an in-chassis rebuild ran about $6,000.00 versus a $15,000.00 motor.
Like Jac Mac said if its unobtanium you don't have a choice. If you can't source a new or reconditioned crank in good shape I can tell you that a good shop if you could find one, can re-condition that crankshaft and it will perform like new if done correctly.
Cheers
Phil

p thompson said:

Don't know why but I missed Jac Mac's reply earlier..

Click to expand...

I wrote it in 'Ghost' mode
Tap it lightly @ both ends of the crank with a 7/8" Ring/OE spanner while its lying on the floor--- if it 'rings' like tuning fork from both ends then take it for crack test---- if the 'ring' is 'dead' or dies away quickly, dont bother, its scrap value only!

Paul, there may be places in the UK that can CNC machine a new crank for you and do all the hardening and polishing as well for less than the cost of a replacement engine. On the west coast of the US there are several good shops that can produce very nice cranks for between $3,500 and $10,000 depending on complexity and whether there is an example model availabe from which to take measurements (or xyz data file). I'm having a flat-crank SBF produced right now by one for in the range of $8,000.

Even if the cost was the same as a new/replacement engine, I imagine the owner will be wanting to replace the crank only rather than the whole engine to try to maintain originality (same engine #).

Cliff, somewhat off-topic but can you elaborate on the difference between a flat SBF crank and a standard one? Would I be right that the flat crank would be a single-plane one?
What are the advantages of a single-plane crank (and a flat one, if they are different) and how does it change the rest of the items you put in the engine? I assume the firing order and cam are also different. Am I right?
In John Horsman's book he complained often about the flat-crank Cosworth DFVs that they ran in Mirage cars. Evidently they vibrate quite a bit. There must be some advantage to a flat-crank engine, though, because they built Cosworths for decades and they won a ton of races....

Hi Paul
Give these people a try.

Used maserati 3200gt : new Spares ? Breakers ? Salvage - Dismantlers

regards
Chris

Paul,
If the crank is steel it can ususlly be built up with weld and then reground back to std. That is assuming that it is crack free. What Jack Mac said about taping it with a hammer and if it "rings like a bell" is a pretty good indication of no crack(s). One of the local engine machining shops I use actually has a bracket on the wall where they thread a bolt into the nose of the crank and hang it on the bracket so they can tap it with a hammer to see if it rings before they even take it in the shop.
A cast iron crank can be brought back to size through a process called "hard chrome" plating.
It is different from decorative chrome or "flash chrome" that we see on parts that are plated for cosmetic reasons. In this process the crank is ground undersize then dipped in wax. the wax is cut away from the journal(s) that need the plating and it is plated with pure chrome. It is a long process and can sometimes take several days in the electroplating tank. After plating the wax is removed and the journal(s) reground to size.
The last time I had one done was in 1992 and it cost $350. Most of the machine shops doing this kind of work have gotten out of this business as the disposal costs to get rid of the hexvalent chromium waste is very high, however it is worth asking around to see if anyone knows of a shop that can do it in your area.
Keith

Thanks for all your suggestions... The crank is definately knackered, possibly recoverable but not sure it's worth the risk.

Enquiring with Maserati gave a replacement figure of £3800+ for the bare crank.. ouch! Add new thrust washers and shells and your up near £4500. :shocked: (got to love Italian exotica)

Anyway, owner has arranged for replacement parts to be delivered later this week so I'll hopefully be bolting it all back together soon. :thumbsup:

I must say that despite the problem with this motor, it's construction is a piece of art really - all beautifully machined mating faces sealed with o-rings and round rubber bead. It's like a well made watch. Just a pity that little thought was given to ease of servicing and that the manual versions (as this is) suffer from an inherant design fault that can destroy an engine in as little as 5000 miles.

Paul Chesman Motorsport - Home Page
Try this company. I have used them for similar types of repairs

jimbo said:

Cliff, somewhat off-topic but can you elaborate on the difference between a flat SBF crank and a standard one? Would I be right that the flat crank would be a single-plane one?
What are the advantages of a single-plane crank (and a flat one, if they are different) and how does it change the rest of the items you put in the engine? I assume the firing order and cam are also different. Am I right?
In John Horsman's book he complained often about the flat-crank Cosworth DFVs that they ran in Mirage cars. Evidently they vibrate quite a bit. There must be some advantage to a flat-crank engine, though, because they built Cosworths for decades and they won a ton of races....

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Hi Jimbo, yes, it's an interesting analysis. There is quite an extensive thread about it here from a few months back - do a search for "flat crank" and you'll find it.

I'm now part way through the conversion of an auto motor to manual, using the auto block and having modifed oil feed to thrust bearing. I'm now fitting the manual heads cams etc onto the auto block as being a later revision it has air-injection for emissions management.

Anyway, as an aside, I thought some of you might like to have a guess at how many bolts/nuts need to be undone to remove the two heads from just one motor?

Motor is out, on the workbench, all hoses removed and heads come off with turbos/exhaust manifolds still attached - the count is just bolts and nuts.

So, anyone want to guess??

My first guess would be 168.

egoman said:

My first guess would be 168.

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You don't work for Maserati do you? :laugh:

There's 200! - but if you ignore the 16 holding inlet manifold and the 12 holding the water manifold, you get 172, so pretty close..:thumbsup: