coated JE pistons plus Alusil - possible?

[KobaltBlau]

Ok, here goes. There has been lots of discussion about honing, rings seating in alusil, etc. I don't want to get into that again here.

My question is this... The OEM pistions were thinly coated with iron to be compatible with the alusil cylinder. I'm curious if anyone knows about iron coatings that could be applied to a JE piston so it could be used in an alusil cylinder.

If anyone has more detail on what exactly the coating was on the original KS pistons, that would be helpful.

The goal here is to get some pistons in there with big valve pockets for high lift cams with a 6-body induction system. Nikasil could certainly be used, but I'm curious if alusil could.

Hopefully I didn't miss a thread on this since "JE" is too short to search for.

TIA

[Rondinone]

We talked about this at great length in the rering alusils thread. Someone, maybe the KS engineer, stated that a graphite coating would be sufficient.

If you're daring, just get a battery and some ferric chloride.

[KobaltBlau]

Oh, shoot. I guess I need to read all 18 pages. Sorry to bring this up again then.

Thanks, Rondinone.

[911pcars]

Andy,
That's a good question. Perhaps JE has an answer since they make the pistons.

I know there's a metal spraying process that spreads a thin, even layer of molten metal on top of other materials. However, I don't know whether such a coating is applicable for a piston.

Sherwood

[garibaldi]

I am not familiar with any coating on those pistons, but logistically, why would you coat a piston with iron? Doesn't make sense to me. What would you caot, the skirts? I would rather have a bare aluminum skirt should the skirts contact the wall during operation and deflect, rather than have an iron coating there which is going to dig into the walls and potentially score them. The rings are iron, and can be coated, but I have not heard of iron coated pistons.

[911pcars]

Christian,
From information I've read, Alusil pistons have an iron coating.

Sherwood

[KobaltBlau]

I second what Sherwood says. This is a standard thing for Alusil type cylinders, Vega, 944, 928, and the 911s that have them.

[Henry Schmidt]

When rubbing two like materials together you get galling, even when lubricated. Especially soft materials. That's why the pistons are tin coated. In the racing world where you find a great deal of titanium, where two pieces of titanium work together you often find one or both pieces hard anodized. this prevents galling. Usually you find a titanium bolt with a steel nut. Same reason. In the case of Alusil or Reynolds Silacite (? spelling) a none coated piston will run fine until you shut the engine off. When the movement stops, the aluminum sticks. I'm have tried thin dense chrome (.0004) in place of tin but the chrome seemed to retain the heat and the piston growth was unacceptable. The guys at Techline lubricants swear there dry film molly will prevent galling but building these engines takes too much work to try to save a buck with reusing alusil cylinders.
If you must reuse Alusil cylinders have them Nicasiled. The Silacite plates better than stock Nicasil and the result is like new cylinders. If your stock pistons are still in good shape you can have the replated cylinders honed to match.

[garibaldi]

cool, I learn something new every day. thanks for the info!

[KobaltBlau]

Thanks for the input, Henry. What is the difference between Silacite and Nikasil (Nicasil?)?

[Henry Schmidt]

Silacite ( ? spelling) is the Reynolds high silacon aluminum that is the basis for Alusil.
As you can see I am the product of the Calif. public school system. I'm lucky I can read !
Nicasil = Nikasil

[911pcars]

I don't keep up but doesn't Porsche use the term "Locasil" (sp) for the description of their current process?

Sherwood

[KobaltBlau]

Oh, I see. I thought that silacite was an alternative plating or something.

What you're saying is nikasil plates well on alusil, more or less. I could look this up, but is the nikasil plating thin enough that you don't have to bore the alusil cylinder at all to retain stock piston sizes/clearance?

[Henry Schmidt]

Nikasil is .003 to .005 " thick. Some boring will be required to achieve the stock size. Plus if you're not using the cylinder, there is probably a reason. when plating, it's best to start with a smooth surface.

[Henry Schmidt]

As I understand it, Reynolds was the first to use high silicon- aluminum blocks. I think I read somewhere that the first aluminum blocks that had no steel or iron sleeves were in the big block chevy run in Jim Halls Cam AM Chaparrals.
I believe these engines were run around 1967 and the engines were 427 cid. This material was the origin of the Alusil and Silamal cylinders used by Mahle and Kolbenschmidt.

[KobaltBlau]

Thanks again, Henry.