Thread: DIY RX8 Engine Rebuild (pic heavy)

Well this is sort of a carry thread from the rx8 owners club so if you want to read though all 10 (and counting) pages then check this link out Click Here Otherwise read on.

First the very short version of how I came to doing this, I went to a dealer brought the car got ripped off, engine was a screwed, at the time did not have to money to pay someone to rebuild so decided with little engineering experience and no experience working on cars to rebuild the engine myself. As it turns out I now have 2 rx8's and a spare engine all being rebuilt by myself

First was the very long process of pulling the engine out of the car, unfortunately I did not take any pics of this and it took about 2 months to do. The main reason it took so long was that I did not have many of the tools required and ordered them as i went so had to wait for delivery. The weather did not help either. But after much work I got the engine out.

I then started the engine tear down process.
















Yes that engine is sitting on my freezer lol. Anyway I then started the process of the sorting and cleaning.
Image below shows all the little bits in their own box (not cleaned yet)

Stripped rotor (not yet cleaned)

Shiny Steel



Cleaning out the seal slots

Oil the gap and rub

There was a lot of rubbish in the groves


The one on the left has been cleaned with cataclean, the one on the right is what it looked like before. Still some way to go yet.


And the rotors all cleaned (with old bearing still in). The rust is because they went though the dishwasher (wont do that again).





The process of checking the side plates.

Here you can see the heavy carbon deposits in the ports.

It was a pain to remove but worth it



Now for the VERY bad news, both rotor housings were screwed. The cause was a apex seal getting stuck in the slot. I originally though this was carbon build up but when i came to the rebuild I could not get the corner seal in the slot easily and when I did the apex seal did not fit. The cause was a tiny indentation in the side of the slot causing the apex seal not to move properly. The only way I can see this happening is that it was always there and Mazda decided to just force it pass the grove.
This is the worst housing, in some places the chrome flak reaches almost 7mm and in pic 4 the chrome is gone





Housings 2, This one does not look terrible, in one place the chrome is slightly out of tolerance at 3.31mm, looking around it is ok to use, but I’m not going to so 2 new rotor housings (ouch!!)


Close up of same damage as above pic.


And at this point my house looked like this




This is the fun day when you get a big box from the USA with all your new bits.











This being my first rebuild there was bound to be a screw up and there was, I forgot about the bearing retainer screw in the front bearing. The gear was fine and I replaced both bearing screws.


Then the rebuild begins, First job is organise everything.


And this is the engine stand I will be using. I had to modify the mounting plate a little (because there was messy welding) to fit the rotary adapter




First job was to put the new bearings into the rotors


I drew lines on the outside to line them up.

That's a nice write up. What i like the most is the fact that you were wise enough to invest in all the little accessories that are needed to make the rebuild a breeze.
It also look that you didn't follow Mazda's side seals gap specification but went tighter, that's a good thing.
I use a bench grinder and some 2000 grit sandpaper on a flat surface to do the side seals since it is a bit faster

Why didn't you do any clean-up port work while you were at it?

G

thank you I decided it was worth doing it right and investing in the tools and I am glad I did. I think the seal gap was 0.05mm, took a long time to get right. I did not do any kind of porting on this engine as I do not have the right tools and did not want to risk screwing it up but I have been doing a lot of reading on porting. I am trying to get hold of some old side plates to practice on before I try on a real engine.

You have got the seal gap right... That engine is going to purr!
Eshaft play? I find that adjusting it is a bit of a pain at times

Putting the apex seals in is messy as well the first time but you figured out the trick on your own... another good trick is to put the rotor's apex in a position where the apex is mildly "compressed", so that the spring placement works the first time. If you're as lazy as I am less than half a drop of loctite will keep the seal's smaller piece in place

Awesome Thread James, Good to see you over here now.
~You will be glad to hear that i am keeping your BHR stuff nice and cosey for you

The best bit is I tried to put it all in one post but it said I was not allowed 110 pictures in a post only 30 lol Have not checked the e-shaft play yet waiting for my stupidly big torque wrench to arrive so I can do the front 19mm bolt up to the correct torque but will update with the figure when done.

Originally Posted by bse

It also look that you didn't follow Mazda's side seals gap specification but went tighter, that's a good thing.
G

Interesting. I guess the advantage to this would be better compression, what is the disadvantage then?