P&C wear...
 

Working on my 1968 2.0 S engine after motorsheister killed it :mad:.

My pistons and cylinders measure out ok on ovality etc. but are only .002" within wear limit (not new tolerance, wear tolerance).

I have been researching options that are not $4500, which is what a new set would cost. Has anyone looked at Swaintech PC-9 coating for 911? Seems to be used in 928 engines to shrink the tolerance successfully for many many miles but would like input on durability and just plain go/no-go on using this to extend the life of this engine without taking out a mortgage on my house. Would be happy for 50,000 miles after rebuild.

.002" within the wear tolerance makes me think you would be a bit early to try it out. I would run it as-is without coatings if you're within the tolerance and you should be fine. By the next rebuild it may be time for such a treatment.

68S are Biral 80s with cast iron bore, same as my '66. Bore to 81 and new JE, that's what I did.

You might even look into having nikasil plated on the bore! Call US Chrome or Milennium Cylinder and see what they say, could be a fun call. Here is an article that says that Nikasil can go up to 0.006" (0.1524mm)

http://www.electrosil.com.au/ElectrosilNikasil.pdf

We've been coating Biral (cast iron cylinders with aluminum cooling fins) barrels with Nikasil for quite some time.
It can be used to return the cylinder to stock specs but more importantly, it offers a far better sealing surface (longevity and fiction reduction) which is especial important when running cylinders with questionable Rockwell readings.
Reduced friction, increased cylinder/ring life and the ability to fit each piston perfectly.
What could be wrong with that?

I like Henry's solution best. I did use Swain tech coatings on an Alusil set I had. It brought the clearance down from .005 to .002 inches. I raced with that set for 5 seasons. They worked ok, but were pretty worn out after 5 seasons.

-Andy

Henry...does the coating (Nikasil) affect the run in time to seat the rings?
I know that hard chromed rings take longer to seat.
Bob

First, for performance, we try not to use chrome rings in a Nikasil liner as the power output of standard ductile iron rings, or plasma/molly is measurably higher.
If the cylinders has proper plateau honing and high quality ductile iron rings, break-in time is relatively short.
The key to long life and proper ring function seems to be in the honing process. Millennium offers the plating quality and honing expertise we require for our engines.
Nikasil is so hard that most standard honing techniques create a RA factor far exceeding the desired limits for ring wear.
That is why we strongly resist the urge to use a bottle brush (grape) hone to treat used Nikasil cylinders.

http://forums.pelicanparts.com/uploa...1375369405.jpg

I've found that plateau honing on nikasil requires quite a long time per cylinder to get the Ra right, and I mean a long time. It also requires a noticeable time longer to seat rings, in my experience with Ferrari engines anyway seating nikasil walled engines takes twice as long as a vanilla iron wall motor. But once they're seated, they wear very slowly which is of course a good thing.

I've used US Chrome before to strip and replate Nickasil cylinders. They charge approximately $200 to strip, replate, and resize each cylinder. So, for about $1000 you essentially have new cylinders renewed. And, their reputation indicates that you can expect normal runs on reworked cylinders. Send them the piston that you would like to match to the cylinder,and they will machine the final to match the piston.

Looks like I am going the nikasil route after a great conversation with Henry on the phone yesterday while sitting in my ambulance on standby. If I could only work on my engine while doing that it would be done by now!