Nikasil failure should I worry?
 

I am just finishing the teardown and clean up of parts on my 3.0 re-build. Motor is a '78 SC, unknown history. I bought it as a core.

One of my Mahle Nikasil cylinders has spots where the plating is bubbling and flaking off. The other five cylinders seem fine and measure within spec. An experienced Porsche mechanic inspected them and believes the 5 are good to re-use. I have obtained a good used replacement for the bad cylinder.

Why would this failure occur? Should I be concerned about using the remaining cylinders?

http://forums.pelicanparts.com/uploa...1427923970.jpg

I searched and could not find any info on Nikasil failures.

Thanks,

I've seen this before and IMHO, its due to contamination before the cylinder was plated. In short, that one was not prepared and cleaned properly.

I believe that that cylinder is original from Mahle. So you are saying that it is a rare anomaly, and it shouldn't occur to any other of my cylinders?

I guess I was lucky that the motor doesn't appear to have been run long in that condition. The crank and bearings look good. Even the pistons are still within spec. Perhaps the magnetic drain plug caught all the debris.

Kolbenschmidt (Alusil) cylinders are not plated so yes, those would be Mahle ones. This issue is quite rare, however based on experience, I would not say that your others are impervious to this. Unfortunately, there is no way to really tell if the others will fail or not.

Regarding debris, Nikasil is barely magnetic and that means such material may not be caught by the magnet. I would open up the oil filter (using a special cutter for this) and lay out the paper element for close inspection.

Thanks for the info Steve.

Unfortunately this motor was on a stand when I bought it, so no filter. And the oil had been drained.

On the positive side the crank and bearings look great with no sign of any debris going through.

My dilemma is trying to decide if I should use these cylinders as is or go to 98s for a SS3.2 motor.:p

When possible, run air filters.

Truly a dilemma,...:)

Remember, there is no replacement for displacement so if you are going to buy new P/C's, installing 98's is a no-brainer to me, despite the cost. Its a long-term decision.

There is another option. Have these cylinder reconditioned. This is an especially good option if the original pistons are still in spec.
Boring 95 mm cylinders to 98mm before replating is an option as well but 3.0 95mm cylinders are a poor choice for this option. 3.2 Carrera cylinders (no head gasket groove) are the preferred choice.

My plan is to replace the stock pistons with J&Es for an increase in compression and to install performance cams. I will be using Webers and backdated exhaust.

At this point I will deglaze the cylinders to get them ready for the new pistons.

If I find some extra money, the 98mm option could happen.

Thanks for the advice

Be careful with the method you use to "deglaze" the cylinders. Some methods (bottle hones especially) can create an RA factor the far exceeds the exceptable range. If the RA factor is too high (generally the case) the ring life expectancy will be greatly reduced. The is a great thread on just that topic. Use your search feature to find the results.

I just finished reading that entire thread. VERY informative. Lots of real world data.

I am thinking the Scotch brite method will work for me. Definitely no grape hones....

I have some JE 10.5 compression pistons that will work for your 95mm cyls, if your cyls measure up such that they'll provide proper clearance (0.0015") for the pistons

You can have that one cylinder replated. Is that a pit/air bubble in the casting or just the shadowing of the picture that makes the defect look really deep?

I am planning on a 9.5 CR, as I want to run pump gas and dual ignition is out of my budget.

There is pitting. It looks like there is corrosion under the plating.

I have already found a single replacement cylinder, so I think I am good to go.

Thanks,

No problem. Just figured i'd ask since you mentioned 3.0L with higher compression, and I mistakenly took that to mean you'd be looking for compression in the twin plug territory.