Alfa Romeo Forum banner

1 - 12 of 12 Posts

·
Registered
Joined
·
650 Posts
I have had plenty of cranks ground and polished! never had a problem at the end of the day the only thing the crank touches is the thrust washers and the seals! The rest of it runs in a bearing of oil!! :)
 

·
Registered
Joined
·
4,239 Posts
Discussion Starter #3
Maybe you've been lucky woody. It's always been recommended to re-nitride after a re-grind.
If it wasn't necessary why would they bother going through the expensive process of nitriding the new cranks from the factory? Just my 2 cents.

;)

from the delta integrale factory workshop manual, covering all models 8v and 16v . . .

In order to improve it's endurance and wear resistance properties, the crankshaft has been subjected to a nitriding treatment.

When the crankshaft is re-ground, after the main bearing jounals and crankpins have been machined to undersize, the crankshaft will have to be re-nitrided to prevent it breaking during operation. It will be necessary to refer this job to a specialist workshop, specifiying that the treatment is liquid nitriding. After treatment, the crankshaft must not be straightened again, although it must be checked that the distortion is within specified limits, otherwise the shaft will have to be replaced.
 

·
Registered
Joined
·
32 Posts
Lots of integrale owners have had problems after regrinding the crank, what happens is that you get mikro cracks that are orthogonal to the rotation direction. These cracks are hard to see and they ruin the oil layer in the bearings.

Note that these are nitride hardened cranks
 

·
Registered
Joined
·
4,239 Posts
Discussion Starter #7
Good to see a photo of them thanks Hector.

Guy Croft talks about them in detail. He has tested several re-grinds and none were race-worthy. Either they were warped or had hairline cranks.
 

·
Registered
Joined
·
224 Posts
I have asked several engineering firms about coating the crankshaft after a re-grind and they all just sniggered. Ignorance is not an endearing trait.
 

·
Registered
Joined
·
4,239 Posts
Discussion Starter #9
Ask Guy Croft about re-grinding nitride cranks!
You can guess what the answer would be.

At least I know Argentina has a large stock of NOS boxer engines and parts here. But of course at a cost.
 

·
Registered
Joined
·
4,239 Posts
Discussion Starter #11
I know of Guy, I have his tuning manuals. He is THE best when it comes to the Fiat/Lancia twin-cam - period
He helped me through my rebuild very well. My thread on his forum has over 17000 views with 35 pages!
Yes he knows he stuff inside out even though he is not so familiar with the alfa boxe, the basic principles of engine rebuilds are the same.

His book is supposed to be the best on the market. One day when I have more cash I would like to purchase that.
 
1 - 12 of 12 Posts
Top