A few months back a friend and I found a great deal on three 13b engines. We broke them down, scrapped the parts that were obvious garbage and cleaned up the parts that were in good shape. I ended up w/ almost an entire S5 engine worth of parts. There were only 2 rotors that appeared usable...


As all the hard seals were intact and there didn't seem to be any fluid leaks we suspected a spun bearing might have been the cause of failure. My friend them proceeded to press out bearing in the front rotor....with his thumbs


It looks fine but something tells me that one is destined to become a clock The other rotor (don't recall if it came from he same engine) Looks fine, there is a little copper showing in one small spot however (see last pic). Would this bearing need to be replaced?

 

That bearing looks fine. What's that spot in the 3rd pic at the 3 o'clock position. Looks like the side seal groove needs some attention in the middle.

 

for the one with the bearing that pooped out, you might wanna look in the FSM, maybe they have a measurement for that? if not i'm sure there is some piston engine way to make it work

 

save your money, look closely at all the pitting in the babbitt, measure the inside of both rotors (bearings removed ) compare your measurements to the stock measurements if they are in spec then press in a new set of bearings , and go on. you only get one shot at doing it right...... but you can have several when you do it wrong .,one more thing,.............. if the rotor is toast make sure you use a replacement that is no more than 2 letters different in(factory) weight code, it helps to weigh the rotors if you can, to compare rotor weights as well

 

You can't resize rotors (where's the parting line? ) and I don't think Mazda sells oversize (on the outside) bearings.

I don't really see a problem with the second rotor's bearing, looks fine to me.

A question. How did the core engine fail? I've never seen a bearing be able to fall out like that and not look completely trashed, and I know from trashed bearings (Fortunately none of them ever siezed to the e-shaft! Can't drive a siezed engine home)

What I would do would be to measure the ID of the first rotor's bearing bore and compare it to the bearing bore of a known good rotor. I never actually checked that dimension so I don't know what it should be.

 

keep them. Goopy Performance sells an oversize bearing for spun rotors, plus it has a VERY generous oil channel.

i have a set of rotors that went through the same thing. i pressed the rear rotor bearing out with my thumbs, and it didn't look all chewed to hell. all the slots are within spec and they look otherwise healthy. i plan to send them to Goopy whenever i'm ready to use them again.

 

i was thinking you could knurl it or something, or loctite....

 

Three set screws like early twin dizzy engines.

 

That bearing is completely fine. If the bearing is tight and no more than 20%?? of copper is showing with no major grooves then its good. Best to spec it anyways...

Clean the entire rotor then spec it out. Looks fine from the picture besides what PvillKnight7 said.

 

So whats your time and energy worth sure you can use the old bearing but why spend all that time and energy to just put in old parts, the bearings are cheep, plus new bearings give you something that used ones do not ,.... better oil pressure. What if it fails again, do you want to do it again ?.Your choice , good luck . If you want specs try downloading the Mazda Speed specs

 

Rotor bearings don't affect oil pressure THAT much, at least not at high RPM where it is most important. Most of the pressure loss is in trying to get the oil into the eccentric shaft in the first place. I forget at what RPM it was, but someone instrumented an E-shaft and found that a certain RPM (7000? 8000?) when oil pressure was 100psi in the main oil gallery, it was only 7psi in the eccentric shaft... when the shaft is spinning that fast, it is very hard to pump oil into it when centrifugal force is trying to force the oil back out.

Ever since i heard about that, I started putting lead-ins on the main journals and lead-outs on the rotor journals. Maybe it helps, maybe it's not significant, but it can't hurt and it takes about ten minutes.

I'm leery of using new rotor bearings because they dramatically increase the break-in time required.

 

I am sure 7lbs of oil pressure is not enough to separate the e shaft from the rotor bearings at any speed, but i do know that for every 1000 rpm you get from your engine You need 10lbs of oil pressure. and you can increase your oil pressure with a different oil pressure relief valve,I would still rather have new bearings,besides most engine break ins are done to set and seat the apex , corner, side seals ,and oil control rings.It is up to you anyway do as you feel .................................

 

i think it was like 12psi@9000?

 

It's a 13B, not a 283 Chevy.

That figure everyone parrots is just a rule of thumb *FOR CHEVIES* that Smokey Yunick said, in the 60's. Some engines are fine with a lot less, some engines require a lot more.

 

Except that pressure has nothing to do with maintaining oil film in journal bearing
Hydrodynamic forces do.

 

Exactly. The reason why we want pressure is to keep the bearings supplied with oil to keep them cool.

Splash-lubricated engines (aka zero oil pressure) were in use in the US up into the 1950s. Some of them even held land speed records, so they were not all low output engines. Sure, they were designed to operate this way with the proper dippers and drip channels and so on, but they still had no pressure feed.

Lose flow through the bearings, the oil in the clearance gets very hot, the bearings get hot, the clearances close up, and bad things happen.

 

It's nice to discuss the theory but practically...replace every old bearing? I think the 20% copper showing limit is a fine guideline.

 

Thanks, lots of good info! I will be keeping the rotors, worse case scenario they can be sent to Goopy...

If I recall correctly, I don't think we even had to pry the locking tab up on that one, which leads me to believe that the dumbass who assembled this motor forgot to drive it down in the first place (in addition to some other shitty build practices). The bearing didn't look bad (less than 20% copper) and the e-shaft appears fine as well.

Peejay: I'm interested in these "lead-ins on the main journals and lead-outs on the rotor journals". I'm trying to utilize all the best-practices for oil and cooling in this build as it will be high comp turbo.

 

That's not a locking tab, just a locator. Some people grind it off before installing the bearing to prevent it from becoming an issue. (IF the bearing spins in the rotor, it WILL warp the bearing and cause a negative clearance situation, unless you grind the tab off, and there's a risk of the bearing being installed a little off and kinking the bearing if you leave it there)

The only thing that holds the bearing in place is crush fit.

 

So 20% or less copper showing is ok to reuse? I have a set of S4 NA rotors that have about 25% copper showing. I'd prefer to reuse these rather than risk new bearings. I've got an S4 turbo oil pump to swap in. I know these provide more volume than the NA pumps. I can also lightly crush the ROPR for higher pressure up high.

The stock stat gear bearings are also showing copper so the stat gears will be swapped for a set with good low mile bearings. I think this combination will provide plenty of oil pressure at idle and allow high RPM use. Thoughts?

 

I've heard you really don't want any copper showing. The shop doing my rebuild measured my bearings and there was no copper showing and they were slightly oval shaped after looking at my measurements they marked down. Let your micrometer do the work and honestly, they said they always replace bearings if they can/someone else can afford it...

 

That's understandable, that some shops would recommend changing bearings. These or similar shops also recommend lapping side plates but won't tell you it reduces useable engine life substantially compared to if you had just a little bit of step wear and left the side plates alone. What happens is the oil seals wear out in only like 20k miles because the hardened nitride layer was removed in the lapping process, exposing the softer much more abrasive iron underneath. It's just a bigger paycheck to them.

I don't lap. I reuse or throw away, depending on step wear.

Sorry this got a little off topic. I'll see how my used bearings turn out when I get the engine running later this week.

 

copper in bearings is bad period. just replace them for peace of mind, longevity and hell they dont cost much.

 

There's always going to be copper showing. The puzzle lock section is always somewhat uneven and the top layer of bearing material goes away rapidly because the high spots are there.

I wouldn't worry about it unless the bearing is scored or shows evidence that it has debris embedded in it.

 

Peejay: I'm interested in these "lead-ins on the main journals and lead-outs on the rotor journals". I'm trying to utilize all the best-practices for oil and cooling in this build as it will be high comp turbo.

Like what I did here-



Other oil system mods I have done-

oil loop line directly from filter pedestal to front main bearing journal and drill through rear main journal for 2 holes (like front) to minimize pressure drop.

drill out plug on oil pump outlet galley and put your outlet fitting here for less pressure drop (plug front cover oil outlet)

port oil pump inlet and outlet cavities

take screen off of oil pump pick up tube and velocity stack the inlet

replace eccentric shaft rotor cooling jets with MFR pieces to restrict oil inside rotors for more pressure at rotor bearings

drill multiple oil entry holes in main bearings grooves

port match stat gears to side housings oil passages

oil pan baffle plate to de-aerate oil and keep it from sloshing

race or FD oil pressure regulator and shimmed front cover relief valve for higher pressure

seal oil pump body to front cover on install

delete front cover gasket and use RTV for less front cover push out

eccentric shaft oil rotor oil thermal bypass delete

competition pan for 2 gallon capacity (slower heat gain) and flat sides for less slosh

order largest FD rotor bearings or MFR rotor bearings (deeper groove)/ flap clearance to remove high spots after press.

flap clearance main bearings to remove high spots and enlarge at edges for e-shaft flex (like taper rear journal on RX8 e-shaft)

Mods I haven't done include-

Set screw/pin/locktite rotor and main bearings for less chance of spin on a seize

dry sump