Nikasil Plating AA Biral Cylinders
 

Hi All,

I was looking at the AA 2.4L 86mm low compression JE pistons and Biral Cylinder kits. Assuming this is a good idea and beneficial, I was thinking of getting the AA Biral cylinders Nikasil plated, but not sure of the procedure. Does the new cylinder bore need to honed to account for the Nikasil plating thickness or is the plating thickness thin enough that it doesn't matter? I researched this forum, but could not find any information.

Originally I wanted to use the original 2.4L Porsche cylinders, but I can only get them safely bored to 85mm.

Thoughts welcome.

You could contact LN Engineering https://lnengineering.com/ and ask. I think the plating was designed for applying to aluminum. Even if it could be done I think the main benefit of heat transfer would be lost.
If you want Nikasil, I would look to buy actual 86mm Nikasil cylinders. LN Engineering offers them. A bit more low budget but I don't know the quality is QSC. https://www.qscusa.com/products/porsche-911-86mm-aluminum-nikasil-coated-cylinders-pistons-set
Henry Schmidt used to sell them, but I think quality can vary.
https://forums.pelicanparts.com/porsche-911-technical-forum/312904-qsc-cylinders-anybody-ever-use-them.html

I've heard at least one builder here mention nikasil plating biral. Wear resistance is one reason to do it.

We do it all the time. I learned the technique by following NASCAR engine builders who have been coating their cast iron blocks for decades.
I rarely run a Biral cylinder sans Nikasil coating.
The benefits are fiction reduction, precise sizing, variable RA factors, better ring options and incredibly durable.
With the AA 86mm cylinders that we've seen, they tend to be a few thousandths over bore (30-40 thou ring gaps on new cylinders) so the Nikasil coating can bring the cylinders back into spec.
It's also a cool way to save a Concours build. New Mahle cylinders are Aluminum so the look is different. Many times the original pistons are still in spec so reusing then in a new bore is cost effective. The key is to get the correct rings.
Keep in mind the Biral cylinders have less expansion so choosing the correct piston material is critical. 4032 (vs 1826) is a better choice. Check with AA to see what material JE is supplying for their application.

Thanks for all the input!

I did more digging on the forum today and found more than a few references to where Nikasil plating from some companies had quality issues (pitting, RA factor, flaking,..). Is there a new recommended company?

Henry - Per AA's website, the JE pistons supplied in the Piston/cylinder kit are 2618 aluminum. I'll check JE's website to see if they offer 4032 alum pistons. Can you clarify your statement regarding piston rings? My interpretation is that if I have the cylinders Nikasil plated, then I may not be able to use the rings supplied by AA??

Thanks again.
-Dennis

Simply put, cast iron cylinders prefer harder rings like chrome plated faces.
In Nikasil coated cylinders, plain cast iron or ductile iron rings coated with manganese phosphate, or molybdenum should be used. It is never appropriate to install chrome-plated rings in Nikasil cylinders under any circumstances. Catastrophic destruction will likely result.

I did not know that so I'll need to check the rings - thank you!

The 86mm QSC Nikasil cylinders were designed incorrectly and this design flaw can result in catastrophic failure.
After the first failure (during a standard break-in process) we sent the failed product to an aircraft company for non-destructive critical analysis and they determined that the failure was caused by an impact (maybe dropped) after the manufacturing process.
The next set we tried was carefully inspected before installing. The second set got past the initial break-in but failed on the first test drive.
The second set suggested that the issue was manufacturing so we got an engineer to analyze the cylinder. He found the flaw. The cylinder used as a sample for the casting was an 84mm cast iron cylinder. That cylinder has cooling fins that go all the way to the base.
Those fins create a very this area at the base when it is bored to 86mm. Reciprocating loads cause the cylinders to crack along one of those fin grooves.

I yet have to find a piston supplier that makes custom forged piston out of 4032. I understand it might be a better choice for cast iron liners and would allow to run tighter clearance, but I think all producers of forged pistons opt for 2618 because it's easier to work with and does offer some advantages in terms of reliability. I've asked CP, JE, Woessner, CPS and Pistal they all told me they use 2618.
Do You know anyone who makes pistons in 4032? I believe Mahle uses something similar to 4032 but I think they are cast, not forged, so unlikely to be produced in small batches.
thanks

If you are unable to order your pistons in 4032 males sure the piston company understands the composition of your cylinders.
Don't over-think this issue. Used what's available given your application.

Henry, I'm planning on using stock, in spec, Mahle 2.4S pistons with new stock Mahle rings in new 84mm AA biral barrels all of which are sittin' on my shelf. What are your thoughts on plating the cylinders and my ring selection? Thanks in advance.