+- Austinsevenfriends (https://www.austinsevenfriends.co.uk/forum)
+-- Forum: Austin Seven Friends Forum (https://www.austinsevenfriends.co.uk/forum/forumdisplay.php?fid=1)
+--- Forum: Forum chat... (https://www.austinsevenfriends.co.uk/forum/forumdisplay.php?fid=14)
+--- Thread: Crankshaft advice (/showthread.php?tid=9803)
Crankshaft advice - Parazine - 13-01-2025
A little collective advice needed.
A friend, who has run a Big 7 for years, has seen the light and bought a project Baby 7. The engine was apparently rebuilt but ran very noisily. We stripped it down and found that a new crankshaft had been installed but there were many problems with the engine assembly, including oval, oversize small end holes in the original, Austin rods, enlarged valves fitted without relieving the head, high lift cam without shortening the bronze cam follower guides, massive timing gear backlash etc.
The engine had been run, maybe 500 - 1000 miles but had obviously shown problems.
My friend removed the big end caps and has found that the hardening on one of the crank pins appears to have failed and the pin is pitted and slightly scored. This might be due to corrosion; the corresponding metalling appears OK.
So, the question is: Can we regrind the crank -0.010 and run it without the hardened layer? Has anyone done this? Could it be ground and re-nitrided?
The crank might be a Phoenix (it isn't marked as such) or might be one of Tony Betts.
Any thoughts, Ladies and Gentlemen?
RE: Crankshaft advice - Robert Leigh - 13-01-2025
My feeling is that it is not a Phoenix, although it is a while since I looked at one. You don't know that it is nitrided unless you have evidence. I would measure it to check it is standard size, and assuming you are not using shell bearings see whether it might come in at -5 thou. The usual -10 thou is to allow for ovality and grooves which arrive with long use.
RE: Crankshaft advice - Chris KC - 13-01-2025
Whilst those photos look horrible, I'm not quite sure what it is I'm looking at.
I was taught that if there's anything you can feel with your fingertip, it's no good.
But it wouldn't be the first time I'd touched out a slight rough patch with 1500 or 2000 grit emery and got away with it.
I can't understand how a shaft could get damaged without something showing up on the white metal or shells - unless of course the previous owner swapped knackered ones for new (without fixing the shaft).
That doesn't look like corrosion to me.
I'd guess it's a Phoenix - I could be wrong - but I have no idea what treatment they apply, that would be a question for the supplier or failing that, the manufacturer. But in terms of establishing the way forward I'd suggest taking it to a competent engine recon shop and taking their advice. They may have the means to test it, or to re-treat it if necessary. I use T&L at Elstow and generally trust their judgement on stuff like this.
RE: Crankshaft advice - Colin Reed - 13-01-2025
Hi,
I would say that Chris is right and a rod has been changed
it probably happend on start up with clearances wrong and there would have to be marks on the bigend bearing
Chris is right take it to a good Recon shop you may get away with just a polish if not a 10 Th regrind on all bigend Journals not good practise to under size one Journal
the shop would then have it re Nitrided Nitriding is normaly 10 Th thick
You did not say if rods are Metaled or shells
Good Luck
Colin
NZ
RE: Crankshaft advice - Charles P - 13-01-2025
For the record my nitrided Phoenix crank was ground 10 thou under 20 years ago and has caused no problems.
That said, it's not always easy getting R4 shells in 10 thou oversize.
RE: Crankshaft advice - Parazine - 14-01-2025
Thanks Guys,
The wisdom is that this is a John Barlow crank. Were these nitrided??? It was running on Austin, white metal rods.
I'm going to fish the crank out of the case today and see exactly what we've got and whether it will polish out, together with a thorough measuring session to check all sizes.
RE: Crankshaft advice - Alan - 14-01-2025
Barlow cranks were nitrided. I’d try polishing before anything else.
RE: Crankshaft advice - Steve Jones - 14-01-2025
Yes, my understanding is that JB's cranks were nitrided as well. At one time I had some details of that but not now I'm afraid.
Steve