Pros, cons?

 

Pro= better sealing for oil and compression
Con= you need to compensate for thrust pressure since lapping 4 surfaces adds up quick and shaft play is not a good thing.

I have thought about milling the area within the inner o--ring groove and having it thermal sprayed. Then have that surface lapped down to stock.
The thermal coating would leave a harder surface with a lower coeffecient of friction. It would be the last time the housings should ever need to be touched unless an apex seal or something comes loose in the chamber.
If you used a surface grinder across the entire surface it would be difficult to cut the o-ring grooves back.

 

scalliwag>compensate for thrust pressure since lapping 4 surfaces adds up quick and shaft play is not a good thing?
I think lapping would make the motor shorter but should have no effect
on end play of the eshaft, unless you mean something else.. i dont understand

matt

 

The motor is shorter so once the flywheel is torqued down there is slack.

 

there was a thread a few months ago discussing about lapping and redoing the spacers to compensate end play. Most of us agreed that lapping the surface on end housing does not affect the end play....... However, it'll shorten the overlength which may lead to not fitting the intake manifold properly.

 

It all depends on how much is lapped off. The better the surface that you start out with the less you need to worry about. But people have a tendency to go overboard and an even bigger tendency not to do the math (X4) I don't have the specs but if you take off enough to mess the bolts up I would suspect that you better use a spacer.

 

.005 is the max you should take off each plate. I think the problem you run into is you don't really know if they have been lapped before unless you bought new ones.


Just for info torquing the flywheel has nothing to do with setting the end play. It doesn't matter if the flywheel is on or off the endplay will still be the same.

 

The other problemis the endplates are nitrided. The hardening "effect" is extremely shallow. So to have longevity comparable to the stock irons, the newly lapped surfaces would have to be re-nitridied

 

I wonder how titanium nitriding would work?

 

pro: you now have a nice flat surface for the side and oil seals

con: you just took off the nitriding so it'll need to be lapped again in like 50k miles just like the old school motors, there is a reason the nitriding is there.

i'm sure there are coatings out there that will work, scalliwag has some good ideas

mike

 

I just talked to a place in Houston called ToolFlo. They used titanium nitriting on a slitter for my horizontal mill that I use for rotors. Actually a local tool grinding shop milled a 1/8" slitter down to cut a 3mm slot and they sent it down to ToolFlo after they ground it.
The coating is 3 microns thick. I gave the guy the size of the housings and he quoted me $150 each plate.
That is not worth it when you factor in the lapping costs on top of that.
I called another shop that does a wide range of coatings including nitriding.
He had me send a picture of a side plate to give them and idea of what they would be working with.
He is supposed to call me with his ideas and pricing.

 

Well my question is how thick is the original nitride coating. Most nitride coatings are less than 5 microns which is just under .0002. Now consider how much wear there is when you take a motor apart and that makes you wonder how long the coating lasts.

 

unless you have a lot of work into the plates its the same price to buy them new ($100-250 each)

mike

 

so it's actually better not to lap the plates (if surface is not badly scratched)?

the CONs and price seems to indicate so.

 

There are a lot of gray areas for certain. If you don't lap the plates the motor "could" burn oil, seals not seat, lose compression. If you lap them without nitriding you can plan on going into the motor again unless you sell it first but it should seal up good.
The options are new parts, really clean used parts, machining and/or nitriding, or crossing your fingers and hoping for the best.
But this is just the nature of the beast. Pay now or pay later. One thing is certain is that if you are going to play, you are going to pay.
My new rapper name is "Scalliwag Dawg Dawg"

 

Thanks for all the good info, guys .

 

Another viewpoint. I looked into this seriously the last time I did my motor and decided to go with lapped (or new if the old parts would sell, and they did).

Had they not sold, they would have been lapped without re-nitriding/coating. Some local friends have many rebuilds under their name with no longevity issues after lapping side/center housings. In Houston there is a shop that will lap all four surfaces for about $150. Did consult with several metallurgists, engineers, and shops as well as researching how Mazda does it (yes I am an engineer geek) ... concluded that it was impractical (meaning expensive) to nitride correctly and there was little data to justify the cost. I believe Mazda does it because they have invested in the technology/hardware therefore it's cost effective to continue. There is better technology out there that would be used if they were to go through the evaluation process again.

The best nitriding process will heat the plates up quite a bit, therefore, you should remove the freeze plugs and lap following the nitriding process. Found folks that could easily do this in Houston but considering the cost for just one set of plates, the pain to do all the prep and follow-up work, I punted. Chose not to do the R&R on alternate technologies in substitute of the nitriding, sorry.

 

Interesting stuff. You wouldn't happen to be Kyle Krutilek, wouldja?

take it easy--

 

damn that girl in your sig is hot!!!! who on earth is that????

 

Yep, YOU are kinda hot Sweetie!

 

this is what I thought, but didn't want to come right out
and say Scalliwag might be wrong I have been accused
of having a attitude

matt

 

i just wanna find a place in/near TN that can do the proper machine work on the cast housings. nobody knows what im talking about when i ask them. that really sucks. im about to rebuild my engine (havent torn it down yet) and i just wanna know if i should lap or not. ya know. haha.

paul

 

Oops! What the hell was I thinking?