Ok, I know I could just send them to mazdatrix but I want to find somone local.

Does anyone have any info on this process, any specs would greatly help in my quest.

Grit,how the finnish looks, how much is too much????


Thanks

GregW
Minneapolis, MN

 

I don't know about Minnesota but here in Houston I've found several places in the Yellow Pages that do lapping. Just look under machine shops. If the one you call doesn't do it there is a good chance they will know someone who does.

A lapping table basically has 3 rotating discs that lower down to the object being lapped and sand an amount off. They are very good and the finish is like a new housing when done.

How much is too much depends on which housings you are lapping. On the old pre-'86 housings you could lap more off since there were no water seal grooves in the side housings. Post-'86 housings can't be done as much but I don't remember how much. Mazdatrix has info on this on their website.

One more thing to remember is when you put a lapped engine back together, the spacer on the front of the e-shaft will have to be changed. Mazda had many diiferent ones that were identified by small letters on them. When you change the thickness of the engine then you change the spec on this. Very important to remeasure it and get it right.

 

Thanks a ton. I will give it a try in the am....

GregW

 

I thought the spacer was just to set shaft end-play, has nothing to do with the length of the engine.

Here's some info on lapping...

from http://www.mazdatrix.com/faq/sidehsgs.htm
A fair amount of material can be removed from the housings - the problem is that it is cumulative. Both in the total per housing (how many times have they previously been cut ?), and the total of cuts done on all FOUR surfaces. You can actually end up with an engine that is so "short" the manifold holes need to be ovaled. The actual limit (which is virtually impossible to measure) is the radius of the end of the stationary gear hitting the radius of the eccentric shaft rotor bearing journal.


What they mean by that last part, is that as you continually make the side housings thinner, the rear end housing gets closer and closer to the front of the engine, and since the E-shaft stays normal length, you can wind up with the rear stationary gear making contact with the rear eccentric on the shaft. I think Atkins or Hayes has a service where they shorten the stationary gear a little to help prevent this.

 

I does adjust e-shaft play but that is determined by the thickness of the engine. When you put the spacer on you have to press it all the way back in. When the engine is lapped and therefore shorter than it goes back farther and a thicker spacer is needed. The different spacers were available from the factory because of minute discrepancies between engines. Not all engines come with the same spacer from the factory.

 

The nitride coating is only .005 deep so you should only take off acouple of thousands,un less you can have them re nitrided.

 

Peejay

You are correct, the lapping of the housings has nothing to do with the end play of the shaft. Rotarygod where are you getting your mis- information from??

 

The spacer is there to allow a little float in the thrust bearings at the front of the eccentric shaft when the front pulley bolt is tightened down. Engine length has nothing to do with it, just the thickness of the spacer vs. the thickness of the two Torrington (flat needle) bearings and the thrust plate.

 

According to the Racing Beat catalog the Nitride coating is typically only .001" to .002" thick on the side housings. They also say they recommend taking no more than .002" off of the side housings as lapping more will result in too shallow a groove for the water seals to bed in. They also state that they believe that removing the Nitride when lapping will not greatly increase wear.

Ben

 

If removing the nitride due to lapping doesn't affect engine life, why does Mazda ship the housings back to the original manufacturer in Japan for lapping and nitriding on the reman motors?

 

Because they can???
Thats a good question actually, it may have something to do with them not trusting anyone here to do it, or not having a lapping table they consider to be accurate enough to do it, so they send it back there,and being that they have the means to nitride, they may as well do it while its there, just to cut down on warranty issues and claims, I can only speculate.. I do know that lapping tables large enough to do side housings are very rare, most tables are big enough to lap valve heads and seats for industrial valves, maybe 6" across at best, and surface grinders are just not all that accurate and heat the metal surface..Max

 

Well, wouldn't you use a different spacer anyways? Since when you make the engine shorter, the stationary gear sits more towards the engine? Meaning that thrust washers is gonna have more play involved, maybe not enough play. I forget which way it is.

 

Should the side housings be re-nitriding? I was thinking of having them re-surfaced then nitriding them. I was also thinking of having the rotors nitrided.

 

run a search using the word "poop" and/or the user BlueTII, he has a great thread on this board and I'm pretty sure he had mentioned something about re-coating the his side housings for the engine he built. i simply don't have time right now or i'd find it and link it for you.

good luck.

 

I did it myself. First I surface ground the housings with a big *** blanchard surface grinder so the faces are parallel and flat. (about .003" per side) At this point everything was happy and flat but I wanted a nice surface finish for oil retention. I made a jig to fit in a big *** boring drill press I have to make one housing oscillate on top of another housing face to face with lapping compound in between. I read up on lapping in a machinist handbook and tried everything from 280 down to 800 grit. 400 seemed nice so I went with that. Not real scientific but hey sometimes you gotta run with your gut. Then I sent them and my Stat gears out for ion nitriding. I read in some Mazda SAE papers how shallow the original gas nitriding surface effect is. My surface grinding probably removed most of the nitrided layer. Ion nitriding goes deeper and is a much lower temp process. Surface hardness was tested at 55-60RC I think. Now I'm sure you're wondering what all this heat did to the nice parallel and flat surface. The answer is nothing. I set each housing on the mill table with a dial indicator on the rotor sealing surface. The indicator has .001 divisions and the needle never left the damn hash mark. Dead on over the whole surface. I was planning on picking up a few sets of housings and doing a few batches but free time has been in short supply recently. Hell my engine has been sitting on the stand for months now.
Oh yeah, no need for different bearing shims.

This is how they looked when they were all done:

And here's a shameless engine shot:

 

DA Sander