Crankshaft MAGNAFLUX ??

[Jerry S]

I am in the process of rebuilding my engine (3.3 litre turbo) for which I was only planning on rebuilding top end such as rings, guides, seals, etc. The problem is that upon disassembly, every compression ring was broken and they appeared to be newer; possibly from a previous owner and the car only has about 65000 miles on it. The reason for the rebuild was several top end leaks were to be repaired and I figured that I may as well clean up the heads and re-ring the pistons. It now appears that some of the ring gaps are greater than 0.004 in which are out of spec and therefore may be the reason for the failure.
DILEMMA-To now go into the bottom end with doubt of the condition of the bearings since the top end is rough. I have read "THE PERFORMANCE HANDBOOK" and Bruce mentions a term called MAGNAFLUX on the crank. I am wondering if this is a repair that can solve crankshaft bearing surface damage if there is any. I would hate to go in and find a damaged surface and find myself looking for another crankshaft. Does this MagnaFlux work? how does it work? and who does a good job???

ps. my camshafts are pooched too as there is some heavy wear on one lobe of each cam (cyl #3, cyl #6)


Thanks Jerry S

[Jim Sims]

Magnaflux is an inspection process used to look for cracks in cranks and other mechanical parts. It doesn't fix the damage merely detects it. Jim

[camgrinder]

Magnaflux is a method of checking the crankshafts for cracks.

Sometimes the top compression ring can break from detonation or preignition. If this is the case the crankcase should be pulled apart and the parts inpected.

The cams should look good after only 65k. Sounds to me like the previous owner wasn't nice to this 3.3 turbo.

[randywebb]

how does it work?
I thnk it works by getting magnetic particles into the cracks and they are then illuminated somehow -- maybe they are iridescent to begin with. If nobody posts on how it works, you might try a Google. It's been used for decades...

Yup, it's just an inspection technique - won't solve the problem if there is one, and won't find any internal weakness.

[911pcars]

and to add to what Jim and camgrinder said, Magnaflux is used only on ferrous (steel) materials.

Sherwood

[Joeaksa]

Jerry,

You place the crank between two massive pads on something that looks like a lathe. Then you turn the machine on and current flows through the part (in this case the crank) and you pour fluid over the crank that helps you see any possible defects or cracks in the part. Its all done in the dark with special lights to help in the inspection.

Afterwards you have to de-magnetize the part before putting it back into service. Have done it lots a while ago while overhauling aircraft engines and once you get good with it its usually fairly easy to find any problems. Any good racing or aircraft shop can do this type of inspection.

JoeA

[norustscott]

Jerry,

Consider picking up our host's 911 engine rebuild book...I think the timing would be perfect. Your question is answered...with full color pictures plus I am sure it will fill in another 100 blanks in your process.

good luck,


Scott

[Dan in Pasadena]

What everyone said, but just to clarify..the term "Magnaflux" is the (or used to be) the proprietary name of a single company for a nondestructive test process that is actually called "magnetic particle inspection".

Doing it properly (at least in my industry, heavy civil construction) requires that the technician performing the insepction be properly qualified to perform the test and read the indications. The guidlines for qualification are contained in a standard named ANST-TC-1A. This is probably more info than you ever wanted, but doing a search will give you more if (God knows why!) you would need it.