Alfa Romeo Forums banner
1 - 14 of 14 Posts

·
Registered
Joined
·
6,167 Posts
Discussion Starter · #1 ·
I'm going to have some work done on my NOS 1750 crankshaft during the winter and might need a bit of advice. These were not nitrided at the factory so I'm going to find a good place to get this done (any recommendations from UK-based BB'ers?). Prior to this, however, I'm going to have it cryo treated. Can anyone tell me what the metallurgical composition of this crankshaft is, as I believe that the company performing this process might need to know this. I'm also thinking of getting other internal components treated e.g. con rods, bushes, gears, shell bearings, valve springs etc.

Thanks in advance for any help!

Alex.

(2000th post!! :D)
 

·
Registered
Joined
·
6,892 Posts
Probably best to contact your local Alfa performance people. Max Banks for one would know the right way to prep your crank.
 

·
Premium Member
71 Berlina 74 GTV 17 Giulia Q4
Joined
·
6,667 Posts
I was under the impression the cranks were nitride hardened at the factory, 2 liters anyway, is that not correct?
 

·
Registered
Joined
·
4,778 Posts
I'm going to have some work done on my NOS 1750 crankshaft during the winter and might need a bit of advice. These were not nitrided at the factory so I'm going to find a good place to get this done (any recommendations from UK-based BB'ers?). Prior to this, however, I'm going to have it cryo treated. Can anyone tell me what the metallurgical composition of this crankshaft is, as I believe that the company performing this process might need to know this. I'm also thinking of getting other internal components treated e.g. con rods, bushes, gears, shell bearings, valve springs etc.

Thanks in advance for any help!

Alex.

(2000th post!! :D)
Hey Aex,

I suggest you drill and tap the cleanout holes for thresded plugs, where the aluminum plugs go or are prior to hardening. I have been drilling and tapping for 5/16-24 set screws. Also do any other machine work you intend such croo drilling for aditional oil feed.

FWIW

Ken
 

·
Registered
Joined
·
6,892 Posts
The 2.0 is, the 1750 is not.
 

·
Registered
Joined
·
561 Posts
Use an Alfetta/giulietta 1.8 crank (they are nitrited) bolted to a 105 2.0 flywheel in your 1750 engine/block.... You will have to bore out the back and fit the spigit bush, but that will be the best/easiest solution.

I have never seen a nitriting finish/treatment as good as Alfa's.
 

·
Registered
Joined
·
2,993 Posts
Clayton, if I had a NOS 1750 crank, I don't think I would be looking for a 1800 Alfetta crank. It's not that hard (at least in the US) to get a crank properly nitrided. Now if Alex didn't already have a crank, I would agree with your advice. For any US readers, please note that the 1800 Alfetta never made it to our shores!

Erik
 

·
Registered
Joined
·
561 Posts
But seeing my advice was for Alex, who lives in the UK where 1800 Alfetta/116 Giulietta engines/cranks would be relatively easy to come by, my advice is quite valid.

You can get cranks nitrited here in Aus too (we are not that backwards), just I have never seen quality quite like Alfa's.

What would you use for a 2.0 engine: a reground, renitrided crank or an unground standard crank in your racecar?
 

·
Registered
Joined
·
6,892 Posts
I would use the NOS one that I have !!
;^)
Seriously, it may not be that easy to find a new 1800 Alfetta crank, even in GB. And you would still have to machine for the trans bush.
Here in the USA, I had my 1750 crank Nitro-carborized for hardening. Less heat so less chance of distorsion.
 

·
Registered
Joined
·
561 Posts
New.... no.

But good secondhand, no problems. It really does take a catastrophic engine failure to wreck one of these later nitrided cranks. I have seen a number of engines spin bearings/run out of oil with no discernable damage to the crank. Not so on the non-treated crank. I have seen poorly cared for engines with a squillion miles on them, and still used the untouched crank for racing.

A friend of mine was importing Alfetta engines into Aus back in the 90's from Europe to sell as cheap replacement engines. As he was more familiar with Fiats than Alfas, he brought in a stack of 1600 Giulietta engines by mistake. He was virtually giving the engines away.

The cranks in these were nitrided.... Mate, were they a valuable item when people found out that they were available and it was hard to get a good 1600 crank. I left one in my workshop when I sold out thinking I would not need it. Coulda sold it a dozen times!
 

·
Registered
Joined
·
2,993 Posts
What would you use for a 2.0 engine: a reground, renitrided crank or an unground standard crank in your racecar?
Well, since you asked. I have been running an unground standard crank. But for the engine I'm building now, I will be running a reground, renitrided crank. That way I can control the main bearing clearances much more accurately.

But back to Alex. He has a perfect, new 1750 crank that he could nitride. The alternative is to spend time and money on a 1800 crank. Then machine for the pilot bushing. Then locate a 2000 flywheel. Perhaps none of these things are all that difficult. Just seems unnecessary when you already have a perfect new crank.

Erik
 

·
Registered
Joined
·
6,167 Posts
Discussion Starter · #12 ·
Thanks for all the input, guys. I did know about the 1800 Alfetta crank option, but I'd already purchased my NOS crank by then! Erik makes the point that my crank is "perfect and new" but that's only to the extent that it is dimensionally perfect and unworn. Of course, its great deficiency is that it has not been hardened.

I guess I need to speak to someone in the business but, from what I've read so far, it appears that the cryo process makes the micro-crystalline structure of any (particularly ferrous) metal more uniform and more tightly meshed together. This not only dramatically improves the fatigue resistance of any item subjected to this process, but it also makes any wearing surface more durable. Cutting tools, for example, have been known to increase their lifespan by four times or more after cryo hardening and so it's easy to see a parallel to journal lifespan, too. What's more, this process (unlike nitriding, nitro-carburising etc) carries zero risk of any warping and is therefore attractive as one method to begin the improvement of this un-hardened crankshaft. The journals would not need to be ground 10 thou undersize either.

So, it seems like a win-win situation as there's no possibility for warping and I can keep the standard journal dimensions. However, if it becomes apparent that this will not be a sufficient improvement and I have to have the crank nitrided in addition to the cryo treatment, I figure that at least the crank won't warp under heat because all the latent stresses will have been eased out by the deep freeze, but I'll then have to regrind the journals to the first undersize.

I guess I'll just have to keep you all posted! :)

Alex.
 

·
Registered
Joined
·
6,892 Posts
I figure that at least the crank won't warp under heat because all the latent stresses will have been eased out by the deep freeze, but I'll then have to regrind the journals to the first undersize.



Alex.[/QUOTE]

Are you under the impression that you have to cut the crank after hardening ??
This is not the case.
 

·
Premium Member
71 Berlina 74 GTV 17 Giulia Q4
Joined
·
6,667 Posts
I've been told by several pretty competent engine builders that you should or at the very least check for distortion. There seems to be differing opinions on this subject.
 
1 - 14 of 14 Posts
Top