Race Engine Forum UK

Hard drive in 35 degree heat in heavy traffic and on the highway today.

The engine temperature was perfect and the fan didn't even come on.

Conclusion: On Sunday I had a blocked breather filter and excess hot gas was building up inside the crankcase affecting performance and increasing the oil temperature significantly.
The boxer needs a very good breather system preferably with a vacuum to suck out the gases.

Today's purchases:

Main bearings
small ends
thrust washers.

All Glyco.
(exchangeable if I need to re-grind and fit over-sized).

Can one grind those cranks? Certainly not if nitrocarburised!

What about post-grind cleaning?

A good def photo of a crank would help.

G

Next month I will have photos.

The cranks are nitride treated and Alfa Romeo do supply 010, 020 and 030 sized bearings so I assume AR know what they are doing otherwise they wouldn't make oversized bearings.
I think the nitride treatment is deep enough up to 030 re-grind.
Many owners have re-ground these cranks and had no issues.

I did read your article about the Fiat 2.0 litre crank a while ago and started asking questions about the Alfa romeo crank.

I'm hoping they don't need a re-grind with just 135,000 kms on them (but of course that all depends on the quality and timing of oil changes in it's history as we know). I will find out in a few weeks.

The supplier of the standard main bearings can change them for oversized if I need a re-grind.
All the car parts suppliers are grouped together within 3 blocks, including the re-grind workshops here in Montevideo.
This is where I'll be getting the small ends pressed in and honed to fit the new gudgeon pins.

We'll see when I open her up again.

Thanks

Chris

No way should you grind. Nobody on the planet can (or would) nitrocarburise thicker than about 0.008" on crank-grade alloy steel and mostly 2hrs treatment (which is costly enough to do) to achieve 2 thou is more common. If it's worn find a good-used replacement.

The fact that OE bearing sizes for regrind are offered should not be taken to mean that grinding without appropriate heat-treatment is acceptable. Fiat were the same but the OE manuals carried a warning that grinding must be accompanied by HT despite the fact that it is almost impossible to re-nitride a crank without inducing microcracking. The fact that folk do grind their cranks (and many mfr used that process) and run them is frankly neither here-nor-there. Grinding will remove the hardened & oil retentive compound layer of carbon/nitrogen exposing the relatively soft core steel underneath - which is a very poor material for a crank bearing journal surface wear rates will go up very substantially.

Take a needle file to one of the regions on an old crank where the oil seal (as they do) has worn thru the compund layer and you will see instantly what I mean.

G

Thanks for the sound advice Guy.

Fingers crossed the crank is ok then. The AR cranks are well known for their durability.

But strangely enough the AR manual does say you can re-grind and does not mention anything about further heat treatment after, not like the Fiat manual.

A good used crank here will be extremely difficult to find.

I will post plastigauge findings once I have it all out and cleaned.

Regards

Chris

Main bearings on these seldom wear on stock engines. If something goes, it's the big ends. If you catch that on time, you almost always get away with just replacing the bearings. in the Netherlands, where parts are much more abundant, people just swap the crank if they get at the damage too late. Nitriding the cranks again is, as Guy says, a specialty that only few shops even try.

There is a modern nitriding technique that may be a solution to the cracking. I see people claim good results with plasma nitriding. Due to the much lower heat used here, there is less deformation and cracking happening than with the high temperature high pressure gas nitriding techniques used until recently. I myself am going to look around to see if i can find a company that does this in the Netherlands, since I have a few cranks that could possibly be reground, but are "worthless" because of the nitriding issue.

I thought it was the main bearings which take the most abuse due to the back and forth force from the motion of the rods.

Well I'll be taking photos of the plastigauge results in Dec.

Keep tuned.

The main bearings were not expensive so I'll be changing them as routine anyway.

Now in regards to polishing/cleaning the main bearing journals.

I see Guy's advice here. Scotchbrite it will be i think.

I would polish the crank with fine Scotchbrite and Jizer or similar. I don't have a picture of this in process because I actually have a lapping tool for this - although if I modify oilways I certainly use that medium for polishing the edges of the modified galleries prior to final polish with an abrasive band. Engine reconditioners do 'lapping' or 'polishing' in the crankshaft grding machine with lapping tongs and if you get them to do it make sure they don't take off too much! Lapping by that method (and mine) must be done contra-direction-of-crank-rotation so it doesn't 'raise the grain'- that is standard practice and violating that rule can cause bearing damage. Contra direction means if the crank (which on this engine - but not all engines - rotates clockwise) is static - the band must be rotated around the crank counter-clockwise.

No, the crankpins are more highly loaded because they take the full firing load, on the mains its shared between them - though not linearly of course, depends on the crank stiffness.

Before advising on polishing I want a photo of the crank to see the oilways and any drillings/plugs in the webs.

G

Before advising on polishing I want a photo of the crank to see the oilways and any drillings/plugs in the webs.

Certainly will do Guy. No plugs exist on the Alfa crank I was informed. How do they manufacture the oil ways on cranks without plugs?

Maybe be around Christmas time. Not sure if you'll be around on the forum then.

Many thanks

Chris

The pictures of the VW Golf GTi cranks below should explain.

A crossdrilled crank will always have plugs in the web to close off the connecting gallery. Effective cleaning is almost impossible unless the plugs can be taken out and then replaced. The gallery behaves like a centrifuge and crud (debris, carbonised oil) will always build up at the outer end of the gallery (where the radius of rotation is biggest), thus - if unlplugging is not possible - one should never apply metal removal processes to such a crank.

A diagonal-drilled one has an oblique drilling and is much easier to make (ie: cheaper) but the lubrication is nowhere as effective. The placement of the drilling on the crankpin (big end journal) is critical. Put it in the wrong place and the firing pressure will prevent the oil getting out at all.

G

Thanks Guy.

This is a picture of a friends Alfa crank. I will upload a much better pic once I get mine out.

You should be able to figure out which style yours is now.

If indeed diagonal drilled it's a 'cinch' to clean, though I would scrub journals and thrust faces with green medium grade Scotch-Brite by 3M (the best) and Jizer or light oil rather than use abrasive.

http://www.google.co.uk/imgres?q=3m+sco ... =115&ty=95

G

Thanks Guy.

If it is indeed cross-drilled without plugs then I'll try the green scotch pad polishing method as you describe. Does make the job easier certainly.

Kerosene/Diesel/Carb Cleaner maybe to clean the oilways and a good squirt of compressed air down each one.

ok pretty convinced now.
Was sent a picture of a friends collection.
No plugs there.

merely for the avoidance of confusion..!

"If it is indeed cross-drilled without plugs .."

you mean if it is 'diagonal-drilled'...!

G