Last year I took the makings a short motor to an engine builder for assessment. A Mk2 S block, small journal 1300 (tuftrided EN16T) crank and a set of rods.

When I pulled out the crank he had a look over it and then said he'd give it a ring test first to see if it was likely to have any cracks. I had done the same at home (some years ago) and thought it rang fine. However, when the engine builder gave it a try it rang like wet wood. I was a bit disappointed, but the crank had cost me nothing many years ago so I couldn't really complain. However, it looked Iike I was up for maybe $1,000 AUD to buy a new crank, and then a set of large journal rods to suit.

Anyway, fast forward to a couple of weeks ago, I was moving stuff around in my workshop. I picked up the crank that I had been meaning to tip and for some reason I grabbed a hammer when walking past the workbench and rang it - rings like a bell!

Trying to figure out what was going on, I finally twigged that the day we tried at the engine builders the crank had bolts loosely fitted in both ends that I had left in to keep the threads clean. I took them out when I brought it back home. Sure enough, when I replaced the bolts in the crank it would no longer ring - they had a significant damping effect.

So, just to be sure, I have had the crank and rods professionally NDT crack tested by a local specialist. All parts passed with flying colours - he even went over the crank twice for me.

Money well spent for me and I will be careful about relying on crank ringing in future.

Tartanred (every day is a school day)

I've had a couple of cranks test fine using dyecheck but not ring properly when struck with a spanner.
Proved to have cracks when uv tested by St George Cranks.
The ring test is a pretty good indicator IMO.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Kev this was a proper UV test by a professional NDT specialist so I am pretty confident in the result. I'm not discounting the ring test as a diagnostic tool but I learnt to be careful that the crank is clean and completely bare.
Cheers Matt