Teflon Coated Pistons

[Curti]

I have a customer in Europe who is sending his pistons to get them Teflon coated.  This is the website that does this process. http://wahl-spezialkolben.de/en/

Is anyone familiar with this process?

[Matt Harwood]

We used to do a Teflon coating on the pistons we put in the LS1 stroker motors we built for the C5 Corvette. We used forged aluminum pistons, which tended to make a knocking noise until they warmed up and expanded, and this coating largely eliminated it. I do not think there was any measurable performance improvement except at the very fringes when we were running a supercharger--we did it mostly to reduce complaints of the knock. I will say that the bright blue pistons looked rather odd and if your hands were even a little bit oily, they were like holding a wet bar of soap, so the stuff is certainly slippery. It seemed to hold up OK in the engine, although we did see skirt scuffing on tear-down (this was a stroker motor with higher piston side loads, however).

 

If you're considering it to reduce friction and improve performance, I don't know how much of a benefit it will provide and I wonder if there was enough improvement to justify the process on an otherwise healthy engine. As I said, we only did it to reduce the knock, not necessarily improve performance or durability. I doubt there was more than a 1-2 horsepower increase due to the reduced friction, if even that much, and that was on a 450+ horsepower engine. Maybe it would help more in a 100 horsepower engine, I don't know. But it's probably way out there on the fringes of diminishing returns in terms of the money:improvement ratio.

[Curti]

The Teflon in  this case is for a 1935 Auburn with original Bonalite aluminum pistons that are basically shot.  Is this a good way to go to get good serviceable pistons as opposed to new modern short skirt pitons?

What are the pros & cons ?

[Mark Shaw]

Maximum continuous temperature rating for the highest rated PTFE Teflon (R) is 550 F.  So I am a bit surprised it works for piston coatings.

http://donwell.com/teflon.htm

 

[Rusty_OToole]

When your Auburn was a late model they used skirt expanders or knurled the pistons. If you have any old MoToR magazines from 1937 or 38 there are ads for these products on nearly every page.

[Pluto]

Because of the above mentioned heat intolerance, I expect he's only having the skirts teflon coated. As Matt says, the benefit is negligible. There are places that will apply ceramic or some proprietary secret sauce to the crowns, but that's a whole 'nother deal.

[Janousek]

Curt,    Most of these coatings are so thin I don't believe it to be a product to tighten worn tolerances.   We used to get pistons coated for snowmobiles and when they scuffed off the stuff couldn't have been a half thousandth.  

 

Cerakote has a high temp coating for the crowns.  Their exhaust coatings are great but I don't see using piston dome coats on an antique engine.  

 

Whats wrong with the Egge pistons for the Auburn? I put a set of forged in our coupe a couple years ago.  It has a few thousand miles without any problems.  

[Curti]

 Brad, personally we use Ross pistons in all of the Auburns.  A customer in Germany is going to go down this road.  Since I am unfamiliar with the process and longevity of the product, I posed the question.

 Heck, I don't paint with lacquer or use leather seals any more. The inside of the engine can be as hi-tech as possible.  If you want to know about my experience with Egge pistons give me a call. 

[Janousek]

Next time I'm on the phone getting parts I'll ask you about the Egge.   I put the forged Egge in our car which shouldn't be a problem.  Most of these Piston places buy the forged blanks and Egge, Ross, or whoever machines them.   I've used Ross in a couple different builds.  Normally when I want to up the compression then I go Ross.  Our 31' Buick easilly has 10k+ on a set of Ross pistons with a 6.5 to 1 compression ratio.  They struggled finding a piston blank that was tall enough to bump the compression where I wanted.  

 

Interesting on using the old pistons this way.    The price of a set of pistons and peace of mind isn't worth scraping a block.  To each his own I guess.