Curious About Grinding Crankshaft on 2 Litre

[focodave]

Why have I seen several posts that suggest it is not a good idea to grind a 2-litre crank?

[djape1977]

because they're hard only on the surface and once you remove that you're left with a piece of pig iron that won't last more than 10k before it needs re-grinding

[BEEK]

im sure there are many who will tell me im stupid and dont know anything. i do agree about the hardness, but we turned hundreds of fiat crankshafts over the years and sold many crank kits. if installed properly and oiled properly they do last. i am not talking a race engine. even though i have run turned cranks in my own race cars with no problems. Guy Croft does not recommend using a turned crankshaft in a fiat 2000. in my opinion he is probably the most learned person on these engines besides lampredi who designed them. i am just giving a personal observation.

[djape1977]

in my part of the world, there is a common belief among mechanics that fiat 132 1800 and 2 litre engines can't be rebuilt. why? because of nitrite treated crankshafts.
guy croft comes from the same school of thinking and experience. in europe, we had very few 124 spiders, and most of our experience with lampredi twin comes from sedans such as 125, 131, 132 and argenta. i'm inclined to believe that fiat used same parts in 124 spiders as in other contemporary models, therefore crankshafts should be the same as in 131 and 132. HOWEVER, something was changed when they came to 1983-1984 argenta 110/120 and these crankshafts can be re-ground and last afterwards. they probably dropped nitrite hardening and went back to heat hardening process.
since we're talking 124 spiders here, it's likely that crankshaft varies from year to year, meaning that early 1800 and 2000 up to 1983 shouldn't be re-ground and later ones can probably be done with resonable degree of dependability.

[fiatfactory]

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[djape1977]

to be honest, i've never seen undersize bearings in original fiat parts packaging.
valves, guides, pistons and piston rings yes but no crank bearings. maybe there's a reason for that?

[fiatfactory]

.

[djape1977]

ok, just goes to proove that i'll be learning as long as i live.

i don't have microfiches but i do have shop repair manuals for 124 sedan, 125 and 132 and there is no mention about undersize bearings in 132 manual while 125 manual lists them.

[fiatfactory]

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[timinator]

. as I said before this whole idea that the crank CAN'T be ground is rubbish and yet another myth (that's been perpetuated in a poorly written book by an arrogant Englishman)

When can we expect your new book to be published? By stating that 4 out of 5 cranks that were reground failed, Croft felt the economics did not prove out. The fuzzy published information that Fiat released during the 80's as to what surface hardening technique was employed meant that the depth of hardening was anyones guess.

Oh, you left out "old and bitter"....

[BEEK]

all i can say is im not arguing with anyone. but i have used turned cranks with no problems for many years. and i have seen factory bearings in oversizes. when i worked at the dealership and still may have some in my box truck of parts. honestly when we were using turned cranks, we never had any problems if you took the plugs out and cleaned them out. too many people dont clean out the crankshafts and have metal shavings inside their engines from day 1

[fiatfactory]

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[timinator]

As I stated earlier, "if the cranks can't be ground, why then do Fiat offer undersized bearings?"

Page 34, "The Chevrolet Racing Engine" by Bill Jenkins ..."Once a crank has been Tufftrided it isn't really suitable for resizing...A Tufftrided crank must also be polished with extreme care. We never use a new piece of abrasive tape when polishing such a crank. The surface quality is so irregular that it may be super tough in one area and yet cut right through the treatment in an adjacent area."

I understand that there are under-size bearings available for Chevy cranks too.

If you can not find a standard 2L crank grind the one you have. If you gind it, and do not race, it might be fine. Or it may fail sitting at a stop light. If you race it and it does not fail good for you.

[focodave]

It is interesting to me that the two examples of racing engine experts who have been quoted, Guy Croft and Bill "Grumpy" Jenkins, are just that -- experts in racing engines.
These guys are (or "was" in Grumpy's case) pushing engines to their limits.
Even brand new components fail miserably in racing engines because everything is being stressed to the absolute max.
I would submit that it is probably unfair to compare the stress on an engine that is used for "normal" driving to that of an engine that is going to be brutally and unequivocally abused in a race environment.
Granted, many good lessons can be learned from racing such as how to tweak and machine parts to withstand severe abuse and gain maximum HP and torque, but is it really fair to say that a machined crank will fail in a gently-driven street car just because some racing engine "experts" have had machined cranks regularly fail in severely tortured race engines?

[fiatfactory]

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