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Strength of 2.0 16v crank?
Posted: November 1st, 2006, 6:08 pm
by Mats
Is the strenght of the crank in the Delta integrale 16v engine a known weak spot or is it possible to regrind the big end bearing surfaces undersized? I'm talking a couple of millimeters here and maybe offset grind it to reduce the stroke.
Will it upset the balance of the reciprocating assembly or is it no different from shifting to a lighter set of pistons and rods?
Posted: November 1st, 2006, 7:06 pm
by Guy Croft
Quote from email to me today by member and noted drag race specialist Greg Demetriadis from Piraeus Greece (16v Integrale):
"... I never had a problem with OEM crankshaft with good balancing. I also make them knife edged (...to lighten and improve aerodynamics). No problem at all at 700 bhp at the wheels.."
As for the other mods, you should consult a crank balancing expert before any lightening mods and you MUST NOT grind that heat treated crank or you'll have no surface harness at all. (I know this from experience and it is also stated in the factory manual).
GC
Posted: November 1st, 2006, 7:54 pm
by Mats
So if I understand you correctly, grinding the journals is a big no-no? What about hardening it afterwards? Nitriding it again? Straighten it and re-balance it afterwards perhaps?
As you maybe guessed by now I really don't know the manufacturing process of a crank. I don't underestimate the importance of correct surface treatments and balance though.
Posted: November 2nd, 2006, 10:01 am
by Guy Croft
Just trust me Mats for now, don't grind it.
I tried a search but I do not appear to explained 'why not?'
You will understand that it is not possible to give detailed explanations for everything, especially 'why can I not do this..'.
I do my best to keep up but it's not easy. Sometimes you just have to take my word and move on.
GC
Posted: November 2nd, 2006, 11:17 am
by Mats
Ok, I'll leave it alone.
Thanks for clearing that out.
Posted: November 4th, 2006, 5:04 am
by Testament
What about the 80mm and 71.5mm Fiat TC cranks? are they heat treated also? or is it ok to grind them?
Posted: November 4th, 2006, 5:09 pm
by Guy Croft
I think it's OK, yes, I often have, but that said, with the 1585cc crank I have tended to heat treat it on competition engines if it needed a grind, being cast rather than forged like the 1756cc one. I think both are probably induction hardened, though I have not proof of this, never had them analysed, not done that many of those two engines.
GC
Posted: November 4th, 2006, 11:33 pm
by ACE-GREG
Mats,
Always, trust Guy.
Especially at engine internals...
Greg