MyE28.com

jimoreno wrote: Oct 21, 2024 3:23 PM I'm about to do this on the B35 pistons that I'm about to install as part of the rebuild. Micro Slick is intended for the skirt area of the pistons and what I've seen is that they tend to leave about 1/8" gap from the edge of the piston. However, it doesn't cover the whole side of the piston pin area, just from slightly below it to the previously mentioned margin. Sideways I have no idea but I'm waiting for the aluminum oxide media to arrive to start blasting the pistons. The top of the piston gets covered with Piston Coat which is apparently a different product with different characteristics.

By the way, are you using oven or air cure? Air cure needs 5 days to cure prior to installation. I've only used air cure since I don't have an oven to cure the items I was handling.

Yes, I have bought air-cure, micro-slick and piston-coat, because I have plenty of time for the build and I figured it's easier.

I'm back from Germany for one week, so I continued the build with some minor progress.

First of all, I started cleaning and prepping the pistons.
You can see just how much soot's on there - especially in the ring grooves. On multiple pistons, even some of the holes in the oil-ring-grooves were fully clogges. The attached picture is the soot from one piston.
I used old rings that I broke in half to start off...





...then I used well-done's "hideg zsíroldó = cold degreaser" - a strong cleaning agent + elbow grease; smoothened the top of the pistons with a dremel tool, then finished off with the ultrasonic cleaner.



Off: does anyknow know what these random pieces of a different metal (steel?) are in the pistons? These are OEM Nural B35 E32 pistons.



I gave the wrist pins a quick polish, just to clean them a bit; then weight matched them to +/-0.05grams by sanding the inside of them.



I also prepped the pistons for cerakote, and I cleaned my engine block thoroughly, now completely ready for assembly.

I sprayed the top of the pistons using cerakote C-186; they are drying right now.
I'll take some pictures on tuesday, we will see how it went.
I used a 1.4mm HVLP gun, because I did not want to buy another gun just for this.
Turned down the pressure to 25psi, full fan, and low material flow. It's was my first time ever with a gun, but it went really smoothly. The material is quite easy to apply. I apply one heavy, and one lighter coat. I preheated the pistons to 40C.

I'm headed back to Germany on wednesday for a final trip this year; once back, I'll move on to cerakote the skirts. While drying, I'll weight match the rods, then I can finally start the engine assembly.
I only have one camera (and only a potato phone):
If anyone is interested, what you like to see more?
Detailed pictures with comments, or a time-lapse of the build?

szacsi72 wrote: Dec 01, 2024 2:12 PM

Off: does anyknow know what these random pieces of a different metal (steel?) are in the pistons? These are OEM Nural B35 E32 pistons.

What is it? It's reinforcing steel. I've seen it on lots of pistons. Where it is and how it makes it stronger I'm not sure, I missed that day in engineering class.

Mike W. wrote: Dec 01, 2024 11:09 PM

szacsi72 wrote: Dec 01, 2024 2:12 PM

Off: does anyknow know what these random pieces of a different metal (steel?) are in the pistons? These are OEM Nural B35 E32 pistons.

What is it? It's reinforcing steel. I've seen it on lots of pistons. Where it is and how it makes it stronger I'm not sure, I missed that day in engineering class.

I normally work on 90s to 00s cars and I haven't seen this so far on any pistons.
It's interesting. One thing I can imagine is that it helps distribute a high contact pressure.. maybe.

Anyway,
Here's how the C-186 turned out:



Turned out pretty nice, for what it is.. first time cerakoteing, first time using a spray gun.
I'll apply the micro slick once I'm home again.
I've decided to not apply it around the ringland, but I will apply it all the way around, not just the two skirts. Probably in un-measureable amounts, but it may help with sealing, reduce drag, but the most important factor in my head is that it could improve the oil film thickness' uniformity by wearing into shape.