Well I just picked up my irons from the machine shop. I had them milled to clean them up a bit. 1 surface needed .005 one .004 and the other two .003. I have read many different opinions on the life expectancy of the motor with resurfaced irons. I think if I can get a solid 50k miles out of this motor I would be happy. Also, is it absolutely necessary to lap the irons? The finish it pretty smooth as it is. Let me know what you think.

 

i read some where that it was not good to resurface irons mirror smooth.

yaw---A housing that is lapped mirror smooth will have little or no oil retention. This is clearly illustrated when applying assembly lube to a mirror finished housing. Rather than spreading evenly across the surface, the lube will bead up much like water on a freshly waxed car.

 

Why did you decide to lap them? Was the stepped wear that bad?

 

He did'nt lap them. They are milled with a flycutter.

 

Yeah. The one iron had about .005 step wear. Plus a nice flat surface is much better than any step wear. Im just wondering how long it will last.

 

Sorry, mis-typed.

Oh, that is a good bit of wear... but I'd be afraid that too much hardened surface was removed.

I've read several threads about resurfacing/lapping and I don't recall anyone having a straight answer as to how much was safe to take off. Some said none and some said a small amount... but that was a while ago. Did you try to dig up any of those threads?

I've never had a need to do it since all the irons I've built with have been < 1/2 of the allowed wear.

 

Yeah i looked through quite a few threads. Seems like .005 was the max to remove. I wish nitriding was a diy process.

 

i had mine done not too long ago. they lapped them and renitrited them. my step wear was about the same as yours. better to be safe than sorry

 

if u can't get them re coated with nitrite they are basically junk..

I had the same issue... I had mine re-surfaced..

then I did a search.. only to discover that I basically ruined them..

I ended up buying a good used one instead.. and the old one became a pretty door stopper

 

You and me both. That would mean I had one sweet garage... much less my own garage in general.

Makes sense. I had read several people saying it's fine to cut them and throw them on. I bet they're singing a different tune now. Or maybe that's for quick/frequent builds for drag racing. Either way i can't see it being a good way to go for general R&R.

On another note, when I glass bead blasted my coolant seal grooves, I got some of the adjacent surface too. I noticed that it gave it a nice matte finish and when I looked at it under a microscope only the finish was slightly changed, it didn't remove any significant amount of metal.



Maybe putting a matte finish on used housings can be a DIY process. It'd be interesting for someone to try it on a larger scale on an engine and see if oil consumption was changed or anything and measure before/after wear.

 

Well I already have a few hours of porting as well as 300 for the grinding so I guess i will be sending them out for nitriding. Who is the closest shop to NJ? Or does anyone know where to get the materials to diy?

 

Did that iron come from an engine with coolant seal problems? The bottom of the lower groove sure looks bad to me...

Dave

 

The biggest threats to your motor involve catastrophic failure from overheat or detonation. I wouldn't worry about wear on resurfaced irons.

 

Nope, I ran it by a couple of builders and they said it wasn't a problem and is normal if you clean it that well: https://www.rx7club.com/showthread.p...hlight=coolant

I think many people never see that kind of thing because they don't bead blast the grooves.

Most people just scrape it with a wee screwdriver and the crud stays in the low spots. I wanted a bare metal surface to hold the seal and hylomar that couldn't erode or break away from pressure.

Besides, that's not that part that I've seen fail... it's the thin cast lip that's on the lower part of the irons that falls into the channel and lets the ring slip out.

 

I wonder if this would work
http://www.zypcoatings.com/Datasheet...NDBStopOff.htm
NDB Stop-off coating is a "Do All" coating for heat treating, being effective for all nitriding, carburizing, and carbonitriding atmospheres. NDB is a safe, easy-to-use water-based 100% inorganic ceramic formulation that provides a hard, abrasion resistant barrier layer on all metals. NDB is proven effective for fluidized bed processing where abrasion resistance is mandatory, but can also be used in conventional furnaces. Apply like ordinary housepaint by brushing, spraying or dipping. Remove residues after use by using steel brush, bead-grit blasting or other mechanical means. There are no environmemtal and flammability problems like those of solvent-based stop-offs

 

I don't think it would stand a chance. First being that it's applied in layers ontop of the metal. It seems to be a barrier more than anything that treats and impregnates into the iron itself. The second thing that comes to mind is that the side seals would chew right through it.

 

I'm pretty sure Racing Beat can re-nitride the irons for you......not exactly around the corner but that's not a service you see commonly offered.

 

Well I found a company that can either gas or Ion nitride the plates for $1.50 a LB. not to bad if you ask me. I just need to read up on which process is better. Would it be worth to have the rotors done as well?

 

would a surface hardness of about 400-500 HV with a maximum depth of 100um be good? Should I have anything else treated as well? Eccentric shaft? Rotors? stationary gears?

 

that search button is a real doosie
https://www.rx7club.com/rotary-car-performance-77/iron-nitriding-473596/

 

I read that post and just about everyother post on here regarding nitriding. Anyway, I just got mine back from getting done and they look great. Ans-ion.net was a great company to work with.

 

Please post pics of the finished irons with the new finish on them.

L8R

 

I'm not sure how well this is going to work out for you. The hardness on factory rotor housings are 1000 Hv. I'm assuming that the irons are at least in the same hardness criteria.

 

Here is a pic.. It not the best but you can get the idea.

 

looks good.
Don't forget to re plug all the oil galleys copper factory plugs, because thy will leak from the heat treat. Also the 2 coolant lines on the rear iron will also leak.

If you address those issues you will be good to go....