hi together,
after bearing failure (big end cyl. no.1) due to problems with oil-supply (sump, pump) my crank needs a re-grind:
its a 681 engine, with 711pistons and flat, stage 3 head, lightened flywheel, rear bowl sump, still on 681 round main bearing caps.
mains are actually on +.010
big ends are on +.010"
grinding all journals, plus nitriding 475pound (600,-€), fine balancing would be en top
difficult decision now...
checked available oversizes for mains:
+.010 , .020, .040
+.030" never existed or arent available anymore?
you cant nitride a std x/flow crank, its made of the wrong material. just regrind it
oh....so i need to tell this the company grinding it.
can you give me some further info about the material why it cannot be nitrided?
i might get it wrong form the grinder: we use the word "nitride" commonly for all hardening processes....even its something else...let me ask him first about the exact method.
It has to be a nitriding material or steel such as EN40B ("B" denotes which type of nitriding process it requires in terms of heat, time, and cooling). I have a Laystall crank that is EN40B which may need re-nitriding if I ever have it ground.Originally Posted by alfas
I think Tuftriding is used for cast iron crank heat treatment.
Last edited by HonkyWhiteTrash; 04-05-2016 at 13:13.
yes you tuftride cast, although you risk the crank bending in the process, just regrind it, we used to have lots done back in the day, in practise it was more about making more money out the job than doing anything meaningfull
today i picked-up my crank.
i asked the guy "what treatment did you use for hardening the crank"?
Nitride
i told him my concerns and he said to me: dont worry, it works.
i spoke with a mate who also runs x/flow enignes in his track cars: Nitride
than i spoke with some formula ford guys: Nitride
finally i spoke with some triumph parts dealers (as the triumph spitfire crank is also cast-iron): Nitirde
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