DIY Iron Resurfacing – what should they look like?
 

I'm cleaning parts to assemble an engine and I followed the Lynn Hannover method of DIY resurfacing the irons without messing up the nitride coating (dry 180 grit, then 5 minutes of wet 400 grit with kerosene on a DA). My irons had some surface rust and stains. I got the surface clean but it doesn't look like I expected. In the light I can see a pattern on the surface, almost like a bunch of small pock marks. Is that how it's supposed to look or did I mess something up? Or maybe I need to spend more time sanding?

Also I know there is step wear, but it's under 0.003" (spec is 0.004")

https://cimg0.ibsrv.net/gimg/www.rx7...49f43df9af.jpg
https://cimg6.ibsrv.net/gimg/www.rx7...fb4e690467.jpg
https://cimg4.ibsrv.net/gimg/www.rx7...64771520d7.jpg

Anybody? I don’t want to do a rebuild with bad irons and I can’t find pictures of resurfaced irons online

I would not do what you are doing. .003" is within spec so I'd just use them as is with no funny business attempting to sand them down or whatever. These nitrided surfaces are not piston bores and should not be treated with the same mindset. While it is true piston rings and side seals are made of similar materials, that is where the similarities end.

I would stop what you are doing and assemble the engine now. I say this because all you are doing is wearing away the hard surface and shortening the life of your irons and any seals that ride on them. Ever torn down a resurfaced engine before? It's pretty bad. Usually nothing is reusable that had any sort of contact with the irons.

If it's not for a client just slap it together.

Im not sure about that. I read most threads on this forum about it before I started. I definitely did not attempt to reduce the step wear and it looks like I didn’t. It’s still the same as when I started. What I did do is remove the staining and surface rust that was on these irons.

This thread convinced me to do it: https://www.rx7club.com/3rd-generati...ppers-1076811/

From what I’ve gathered, you can do this a lot before you get through the coating

if you do do this you are locking yourself into OEM seal territory. Plenty of youtube videos showing people getting low compression using aftermarket seals after doing a resurfacing.. as stated above your better off just using them as is. I can guarantee you won't get noticeable compression gains .

Whats the difference in the thickness of the nitriding on an 13B plate versus older 12A plates? Maybe it works for 13Bs.

This is an S5 13b I’m building to drop into my FB. I did order an Atkins rebuild kit already with OEM corner seals and plugs.

I’m surprised to see such a different reaction to doing this in the first gen section than the third gen. I was expecting some feedback on how the irons should look but it seems like everyone thinks I ruined the nitride layer? Not sure how I took that much off when the step wear didn’t change

To be fair the third gen guys blow motors up like its no body's business .

I can’t argue with that!

Alright, I cleaned up the front iron with only wd40 and a few scotchbright pads. After a while I got to this point. It doesn't look perfect but is it good enough? Interestingly I got the same textured look I saw in my center iron above, so now I'm wondering about that one again too. Thoughts?

https://cimg7.ibsrv.net/gimg/www.rx7...19c064512a.jpg

It looks decent. Scotchbright is what I've used with fine results.

Ugh... that side seal groove is going to eat oil control rings. I have a pile of 12A side housings I won't use because of wear like that and they don't look nearly that bad.

It also looks like it's worn through the hardening anyway. You can see a definite change in "surface texture" in that vertical trough.

All is not lost, Chips Motorsport will grind, lap, and re-nitride housings for something like $700 a set, which includes new core plugs everywhere. Basically they are completely remanufactured. Great deal for what you get. Is why I have a pile of 12A side housings, and haven't scrapped them.

The key performance factor is not the 'finish' as much as it is the flatness of the surface.

Hand-refinishing to eliminate step wear will not completely restore flatness. It just makes the variations more gradual & harder to measure.

The only way to get a properly flat iron is to have them lapped professionally, IMHO.

Agreed. Chips rebuilt my Streetport 12A and the lap+re-nitride service is a must. His work is perfection.

I picked up another set of s5 irons in much better shape for $300, so for now these irons will sit on a shelf in case I need to get them lapped and renitrided in the future. Too many people think the coating is messed up for me to feel good about them, plus the step wear is close to the limit anyway. I’m going to stick with scotchbrite pads from now on.