Hi everyone,

i disassembled my engine yesterday. This one came from Canada out of a scrap FD. I didn't know if it was runing or not. I didnt found any metal in the oil pan. But i sow that the turbo was broken. So here are a few pictures of the Parts where i would need a qualified opinion from you. For me every part looks surprisingly good and has no scratches that i can feel (exapt the rear stationary gear bearing) That has a scratch that i have done i guess.

Sorry for my bad english.

My plan ist to reuse everything and just replace the mentioned stationary bearing.

Here you can finde the Pictures:
https://1drv.ms/f/s!AjpI-CcNBgVqichVZoEpgKbs_NksNQ

Thanks for your help!
Can you also tell me if the surface on the side plates in the area of the combustion is normal? It feels totality smooth but has this broken surface look.

Thanks for your help.

 

It looks like you got a really good engine to start with. Few things I'm noticing -

- The oil metering pump is the newer style Mikuni OMP that is desirable. You can read up on that.
- Irons look good. Big thing is the water passages are SUPER clean so it's had regular coolant changes and was taken care of. I don't see any broken walls around the coolant seals or anything.
- The bearing in that rear stationary gear has an edge chipped. The gear itself (from what I can see) looks OK, you can just get the bearing for a reasonable price and press a new one in.
- Rotor bearings look good, I don't know if I would even change those.
- Hard to say on rotor housings, they need some more cleaning.

In general you have excellent parts there. Here are my recommendations -

- The irons look flat, if you don't have any grooves in the irons that you can catch a thumbnail in and the water jacket grooves are all good, run them as is. Yes it would be nice to have them lapped and re-nitrided but the shipping costs from Germany to wherever would be a killer. You wouldn't gain enough to make it worth the expense.
- If the rotor housings are good, smooth, no big gouges or flaking you can run them. New rotor housings will give the best compression always, but that's a substantial sum. But, if these housings are decent you can recoup some cost reselling them.

Also, it looks like someone did some light porting of the outside of the intake ports, probably gasket matching. Looks fine, nothing to get excited about.

Get some quality apex seals, do a good job fitting the side seals, and you'll have a nice, tight, engine.

Dale

 

Thanks for the Help!

I also saw that one or two water passages in the rotor housing are like 70% blocked. Is this necessary? or can i open them up to increase the cooling

 

There is something to be gained by porting the coolant passages. Barry Bordes did a lot of science on this -

https://www.rx7club.com/3rd-generati...em-fix-989811/

I will say that properly porting them isn't as easy as you would think. I don't know how far I'd go down that rabbit hole. Some of the restriction is there for a purpose, and if you just open things up "because it looks good" it may actually be detrimental.

Big thing with any build is realistically knowing what your goals for the engine are and keeping costs in check. You can easily spend tens of thousands on a motor, but that expense may not actually get you a good bang for the buck or would be such overkill that it would just be a waste of money.

Dale

 

I agree with Dale. The engine looks good.
You need to measure every thing to establish fit tolerances.
Attached is a worksheet. Unfortunately it is inches rather that mm.

Don't open any water passages except the two noted in the Thread suggested by Dale. You should actually add a restrictor in the passage below the two ported passages.
Barry Bordes

 

Hi guys,

thanks for the insprection sheet. I also done some work on that to make for each part a sheet for measuring and work to do. I will double check your values with my`n. There are some new (clean) pictures in the link of the top post. Every part looks very good. I`m really happy with the engine. Now my plan is for the engine:
- machine the rotorhousings for a flat surface to the side housings
- clearance the rotor`s
- lighten the rotor`s
- Clean the water passages. Only sharp edges and cast inperfections
- port the Oil pump flange and the oil filter flange
- Turblown stud kit

Can you recommend the Atkins cryo seals and gasket set?
Do you know how i need to seal the stud kit on the end?

Br Christian

 

Christian I like the Mazda stock apex seals. They last forever when you flatten the housing with my cooling mod.
Mazda did a lot of research to fine the best metal combination for the housings.... and the best way to lubricate them!

I like the Atkins soft seal kits but only use their extended length side seals. I use them for zero clearance corner sealing.
(see attached)

As for replacing the bearings (rotor and stationary gear). Use the thinnest bearing (largest clearance) for the best fit - the yellow code.
If you use any other color/size you will have to polish the bearing to have the correct fit and it will look just like the bearings you have now.
Barry

 

Christian,
From the video there seems be an excessive build-up of carbon on the rotor sides.
Did you check side seal clearances before disassembly? (most people don't)
Are the ports stock? (as in cutting into the oil seal locus area)
Was the previous owner running heavy pre-mix?
How easily did the oil seals come out? (like bad softened o-rings)
Barry

 

How do you check that before disassembly?

 

Hi Barry thanks for your knowledge and effort.

Didn't check the clearance of the side seals.
The ports are stock.
The oil seals came out pretty tight and did look normal to me.
But that's my first engine I disassemble. First time in the rabbit hole^^

Can you explain how you do the zero clearance side seal?

 

I use a dremel diamond wheel in a shop-made fixture.
For details search "Zero Clearance Side Seals" or threads started by me.
Barry

 

Check this clearance with a feeler gauge before removing the side seals form the rotor.
You have 12 of these leaks per two rotor engine causing blow-by.
This clearance is critical... too tight will cause side plates to score and corner seals to brake.
Too loose... and you have low compression and blow-by.
Notice also the extra carbon on the rotor from the leak.
Barry

 

Hi Barry,

thanks for your help. Lets see if i have the time to do this mod. But thanks for your efforts! Could you have a second look at my link in the first post? I put in some later pictures of the stat. gear bearing. and of the Rotor housing.
stat gear: Do they still lok good? i cant feel any marks or so. but they dont look "nice"
Rotor housing: There is a piece broken of from the riding surface. It is only on one side at the bottom of the chamber.

Can i still run the housing? other wise it is perfectly in spec.

 

The housing is compromised and will leak about the same as a set of normally clearance side seals... not good but acceptable. It was caused by the small triangle end of the apex seal.
The solution would be to reverse the apex seal..... putting the triangle on the opposite end for the next running period.

The stationary gear bearings are not optimal either. That being said they look worst than they are. The eccentric shaft runs on a .0015" film of oil.
The only time it touches the bearing face is during start-up. At that time any small abrasive particles from dirty oil would be embedded in the soft Babbitt coating of the bearing shell rather than allowing it to score the eccentric shaft.

So to make it perfect ( and most expensive) change the housing and new yellow coded bearings..... but the parts are serviceable.

Barry