This project has taken forever but heres an update. I ground lapped my side housings myself. I made an aparatus to lap my housings and they turned out great. I then sent them out for Ion Nitriding (along with my stationary gears ) Between last night and tonight I filled and repoted my aux ports because I won't be using the sleeves anymore. I am going to give it one quick lap just to make sure everything is flat after nitriding. Next step is engine and trans assembly. The engine is going into a VW Beetle and will be turbod. I am rebuilding a porsche 901 5 speed trans out of a 914 with the diff flipped (so it doesn't have 5 speeds in reverse) and modified shift rod and nose cone. More pics comming as I make more slooooow progress.
Feel free to comment, question, and criticize

 

I bet that's going to be one fast bug!

I don't know for sure, but I bet there isn't to many bug motors putting out the power of a 13b.

 

Pics of the lapping jig? The result looks great, assuming it's flat.

 

No assumptions here, pre-nitriding I set each plate on the mill table with a dial indicator on the surface, zeroed the dial and started moving the side housing around. The needle never left the hash mark on the dial. Flat and paralell I will be re-checking using this procedure and then lapping one last time with a finer compound.

The sad thing is I won't be able to really push this engine, the trans won't take much more than 300hp. First gear is a weak link (no slicks, no hard launching) so I will probalby run boost cut in first with a limit switch and a 2 stage boost controller. A 915 porsche box or some of the custom dune buggy transaxles would take a lot more but I would end up spending about 3K on a trans and half shafts. Since I knew from the start that I wouldn't be pushing too much boost I decided to stick with the NA rotors (this is... was an NA motor to start with) and keep some low end power. Should make for a very drivable very fast car till something breaks again.

My lapping project started with reading the machinist handbook and deciding I could get away with just rubbing the faces of my housings together with lapping compound and lubricant inbetween. I have the advantage of alread having flat and paralell housings after I surface grind them so lapping is just to achieve a surface finish. I tried just rubbing two plates together face to face with lapping comound and lubricant inbetween, my arms got tired and I started looking for a better way. I used a boring machine (low rpm) and crank with an offset pin to generate a circular path which rotates the intermediate housing over the front or rear housing. The housing being rotated actualy makes a path very similar to the rotor, it moves in a circle and rotates at the same time. I would put some pics up but its just a boring machine with a crank mechanism I machined, not much to it. I have a spare 12A and now I'm tempted to try welding up the ports, grinding it flat and turning it into a P Port motor... except I don't have anything to put it in.

\/Pic of a housing post grind, pre lapping \/

 

That looks good! I wonder if you would really need to lap them. I think they would work fine as is.

Only because I can see the original Blanchard grind marks in my stock irons.

 

Now that's a very interesting technique. I've never heard of anything like that before.

 

Awsome project!

Respected rotary guru Paul Yaw (yawpower.com) recommends surface grinding and then a light lapping to take off the peaks, but leave the valleys for lubricant retention.

You can watch oil bead up on a perfectly smooth lapped surface, whereas it soaks into a coarser surface.

As an experiment I Phosphated my lapped plates to provide lubricant retention (it really "sucks" up the oil) and to my surpise it was still mostly there after 4,000 miles. The thin phosphate layer wetsands off instantly w/ 1500 grit so I didn't think it would last much past initial start-up.

 

Yo how duz I make my 13A go 1,000,000rpmzzzz? haha jk. Glad you guys find it interesting. Lapping does make a very visible difference in oil retention. I picked up a housing, carried it for maybe half a min. set it down and my whole damn palm print soaked into the surface.

BLUE TII: Got any pics? Did you end up with the cool gunmetal gray finish on your irons after parkerizing? I've been looking into alternatives to painting my irons, I dont like em rusty and paint is pretty temporary. The idea of dipping a finished surface in hot acid kind of scares me though. I have used dilluted phosphoric acid to prep for welding things and if there are any impurities you end up with a very etched surface.

Aaron Cake: I was looking at lapping tables in McMasterCarr and figured well all it has to be is flat... my housings are flat why not make one a lapping table for the other surface, let em lap eachother. I don't know if you would get good results just straight lapping (no surface grinding). Since it is constantly orbiting just riding on high spots it just might work. I'll have to give it a try when I get some time with some real coarse compound. I have a cooked 12A and a good 12A which will become my test monkey for some projects/ideas like this.

 

Since I didn't have access to a dip tank I just heated up the housings and rubbed the acid onto the wear surfaces and ports (bare metal). I was too lazy to do the rest of the housings surfaces, though I have never had a problem with them rusting.

I thought manganese phospating would be fun to try as well since it is a better lubricant.

Pics on this thread.

https://www.rx7club.com/rotary-car-performance-77/pics-blue-tiis-engine-build-new-type-primary-port-489429/

 

Man! I just read that thread again! It is awsome! I am totally thinking about the your porting ideas and phasing while doing my street build.

I think I can surface grind to a finish way better than the above posted pics. Do you still think a lapping would be nessecary?

 

Define better. After lapping the finish is very dull and looks like is it rough, which it is on a very fine scale. Shiny smooth finish is not desirable. They are not easy to grind, the surface is very hard like 60RC and then you skim a couple thousands and your down to base Iron again. You would probably have to switch grinding wheels to get a real nice finish. With my jig I can grind a housing as fast as heat build up will allow and not worry about the finish. After grinding the housings are flat and smooth, I only did the lapping to get the surface finish you see in the first set of pics which is pretty much the same finish you see on BLUE TIIs housings. For all I know grinding alone is adequate for oil retention. Try it, post pics and results

 

I'll post pics of my lapped irons later

 

as always, i am impressed with your work.

i wish i had access to some of that machinery so i could see just how much i could get done for myself instead of sending my parts out.

 

I like this project your doing, and the porting looks very nice. I just wanted to tell you something that happened to me a while ago, to maybe help you save a motor. I built a engine for my daily driver three years ago, and ported it very similar to yours, I then used Devcon to smooth the 5th and 6th port, just as you did. I had let it dry for two weeks before I put it together. After it was assembled, and I drove it for about 3 months, I noticed the power just wasnt there anymore. I pulled off the lower intake, and the fuel had been making the devcon soft, and was slowly pulling it into the intake port, and was very close to breaking off and falling into the engine. I didnt attempt to chip it out, for risk of peices getting into the engine, so I just ported two turbo II front and rear plates, rebuilt the engine, and never went back to 6 port again. I dont know if this is has happened to just me, or I put on the devcon too thick, I am not sure. But it was a close call, just to let you know what happened.

 

If you were worried about the epoxy and really wanted to keep the 6 ports I have heard of people pressing a slug of Delrin or similar material and porting it to the right shape.

 

Thanks diabolical1 and GtoRx7, I just wish I had more time to use all my resources for my own projects. I think the feeling must be similar to how all those old guys felt before viagra. Between the family business and going to school full time at night I end up sacraficing sleep just to get a few hours of car time.
GtoRx7, about the epoxy. I used Devcon Liquid Aluminum filled epoxy #10710 http://www.devcon.com/techinfo/108.pdf
It is rated "very good" for gasoline chemical resistance. What Devcon epoxy did you use? First hand experience is 10X better than any datasheet though, I will mix some up and let it soak in some gas to see what happens to it. I have seen the pics on the board of the plastic inserts that someone made. Considering I have a lathe sittin there and some teflon rods I probably should have gone that route... too late now on those housings. I was also reading about the weakness of the 6-port rear housing, I'm going to have to think about this.

 

Both the NA and TII pre '89 (S4) rear housings have the weakness at the rear upper dowel area. '89 and later S5) reinforced this area with additional material cast in a gusset from the oil filter land to the rear upper dowel land.

I had a S4 TII rear plate fail on me and replaced it with S5 plate. The 4 port end housings ports are a little different between the S4 and S5 , but can be ported the same; I believe the 6 port end housings ports are the same S4 to S5.

 

Exactly, I have seen this before, and it worked out great for them. I would trust it more than the steel putty.

 

I know I'm totally dragging this up from the depths of nowhere but I just ran across this youtube vid
http://youtube.com/watch?v=fXfk0DrxAYY
Who's stealing my ideas!!!! jk, good to see someone else is trying it.
This is pretty much exactly how I lapped my housings after grinding. I used a much larger boring drill press that spun slower and my housing was allowed to free spin as it oscillated much like how the rotor rotates around the eccentric shaft as the shaft turns. My crank pin offsest is probably around 2" and ran at about half the speed of the one in the video.
Unfortunately my engine is still on the stand, still working on the Porsche trans and making a shifter for it.

 

Where do you get your lapping compound, what grit, and what did you use for lube with the grit?

Thanks

 

As far as I'm concerned you can drag stuff up all you want.

I've taken the lapping after grinding advice and I am on it. I am trying to get the place I work at to order a 36 grit wheel for our big surface grinder. We use 46 grit now. I keep telling them that we could really use this. Well, at least me. The lapping vid is oh so doable.

 

I ran 400 then 800 after a really thorough washing in between. You can get the stuff in quart paint cans from McMaster-Carr. $25-60 a pound. I mixed in a little mineral spirits in with mine while lapping because thats what the machinist handbook said to do. I would really like to know how the engine in the video turned out and if the housings were re-nitrided.

 

nice idea on the lapping. so i'm guessing it's really not neccessary to lap in a figure 8 pattern?

 

It's important to keep everything moving. I was working with flat pieces to begin with (ground) but if you are trying to resurface worn housing you are only riding on high points until the lapping compound does its work and takes em down. If you only move in a small path/motion you risk the high spot lapping the opposing area into a low spot. My jig kept the top piece constantly rotating on two axes so contact points were constantly changing. I have some spare 12A engines I will give a shot with this summer, no grinding, just stages of lapping in my fixture to see what kind of results I can get. My ground/lapped housings were flat and parallel to under a thou (the dial indicator never moved off the "0" hash mark!!) We'll see how close I can get without grinding. It would almost be a shame to find it was that easy, I spent a lot of time rebuilding the automatic feeds on the surface grinder just for this project.

I used a 46H no problem.

 

Zombie thread resurrection!!!

After a loooooong hiatus I finally got this engine off the stand and running in an RX8.
Lesson learned, if you are going to have your side housings nitrided replace all all the coolant and oil plugs. I think most of the builders that offer the service do this, or at least Chips Motorsports does. It's not optional....

Anyway, I'll continue to report back any findings good or bad.
I think tracking compression is a good idea. I have a scope and a pretty good pressure transducer that should make it pretty easy to get real numbers.