I posted this in a different thread of mine in the 2nd Gen section and it didn't garner any responses, so I figured maybe it deserved its own thread.

I'm figuring out what direction my rebuild will take. The bearings from my previous engine are worn, so I'm going to need new ones, but once I price out the cost of the bearings + installation (because I don't have a press) I'm getting near the cost of just buying new Rx8 stat gears with bearings included. This makes it seem like for the few dollars extra I'd need to spend, I would end up with the hardened gears and the improved bearings. The engine is a Series 4 NA otherwise.

Now I know two main differences with the Rx8 gears need to be accounted for:

- The oil supply hole on the rear gear needs to be ovaled to match the hole in the FC iron.
- There is no groove for the o-ring on the rear gear, as this o-ring was placed on the iron. Either the gear must be machined to add the groove, or sealant must be used on the flange where the o-ring normally mounts.

My question however boils down to this:

- The oil clearances are different for the Rx8 bearings. Does this mean I need the Rx8 e-shaft? What I am reading online seems to imply the FC shaft would work fine, which sounds good to me since the Rx8 shaft is lighter and I would like to avoid balancing costs.

- From what I read, the FD and Rx8 front stack have beefier components. But the front stack includes the counterweight, which again puts me into balancing territory. Is it possible to use the FC front stack in combination with the Rx8 front stationary gear? I can't see why it wouldn't work (because from what I read the gear dimensions are identical). If not, can you use an Rx8 / FD front stack with an S4 counterweight?

Thanks, Chris.

 

for your first question, i know for sure that there is no problem using the older shaft with the gears/bearings. i confirmed that with Pineapple a while back.

for your second question, i read somewhere that you need to match the thrust bearings with the stationary gear you're using. presumably that would apply to the spacer as well, but i can't say for sure if they were changed as well.

 

actually, while we're on the topic, i have a question.

with regards to the S5 T2, which thrust setup does it use; the older style or the newer style? i ask because from what i've read on the subject there is some fuzziness.

for example, i've seen where some sources have said the new thrust bearings came as early as 1989, and other sources have said they came as late as 1993. i'm guessing the JC Cosmo was the driving force to the changes, but did they apply them to the T2 as well?

i have a S5 T2 block, but i bought it as an empty case, so i have no clue what the OE parts were.

 

I actually emailed Pineapple shortly after your response, and Rob was able to clear it up. I also asked if you could use the S4 counterweight with the Rx8 front stack. This was his response:


"The new RX8 gears have new bearings and a new rear main seal.

I would not spend the money on machining for the rear stationary gear o ring. Just make sure the surfaces are clean and use a good quality silicone sealer.

You can use your S4 e -shaft and all balancing/drive parts with the RX8 gears or even with the RX8 e-shaft for that matter.

Your correct, if you wanted the larger thrust bearings, you would need to change all the related parts.

Take care, rob "


It was pretty cool of him to respond so quickly; it was about 1/2 hour after my email and he answered my questions perfectly.

So from what you've told me and what Rob has told me, we can conclude that:


- You can use the Rx8 stat gears in an otherwise FC engine, provided you account for the missing o-ring and match the oil-supply holes in the rear gear.

- You can use the earlier front stack components with the Rx8 gears.

- If you want the larger front stack components, you have to change all the pieces together. So no S4 counterweight with otherwise Rx8 or FD front stack components.

- You can use the Rx8 e-shaft with the S4 components as well.