I recently rebuilt my 12a with lapped plates, new seals, springs etc and two nice housings. On a bench test using a bell housing and a starter I got 110psi on all 3 faces on rotor one and nearly the same on housing two maybe 105psi.

Everything looked great until I started the engine and heard a clunking noise. I lost all compression on rotor 1. After tear down it turns out that somehow the rotor came into contact with the housing!!!, It bent the tips of the rotor enough to hold the apex seals in so tight I had to hammer the seals out! The front stationary gear also showed damage, a little chewed up.

So I humbly admit I must have made a mistake but I just can't figure out how this could be possible. All the bearing are original, and the motor did run smooth before the rebuild but had oil and coolant leaks. Weirder still is that this housing is the original housing from before the rebuild.

Has anyone ever seen a rotor his the housing? Hows that possible?

 

Gear ring in the rotor came unpinned & slipped indexing?

Rotor mis-indexed on stationary gear?

Fractured stationary gear or gear ring tooth?

 

or rotor was upside down....

 

Lapped plates can change the lettered ring on the back side... Did you measure your end play...?

 

the ONLY way the rotor can hit the rotor housing, is if the bearing/stationary gear is bad/way out of clearance.

how are the bearings? how is the eshaft? the stat gear? and the rotor gear?

 

Wrong. A rotor can also contact the side irons if the rotor housings are warped. it usually happens around the spark plugs. if the rotor is wider then the rotor housing, then you'll be in for major trouble. the FSM has a measurement for compairing a point "A" at the top, to three places "B,C, and D" near the plug holes.

Was the engine rebuilt due to coolant seal failure/overheat? betting it was...

 

I mean I'm no engineer & I haven't spent time looking into this besides the fact that I just spent the last 30 seconds thinking through in my head how my scenerio posted above could of actually caused a rotor to hit the housing.... If the lapped plates loose however many a thousandths of an inch each, he uses the orginal ring, and end play is now excessive, couldn't the bearing have just enough room to walk in an unusual pattern...??? Just saying.

 

so did it hit the SIDE housing, or the ROTOR housing.... i've never seen one actually hit the ALUMINUM housing. and like j9fd3s said, and i got confused, you could only do this with WAY WAY excessive bearing clearance. like. a good 10th of an inch. you would notice this putting the rotors in.

 

yeah i just reread the original post, and he doesn't say rotor housing or side housing. he also says the stat gear is damaged, so F.O.D. ?

 

likely, but what, maybe injector atomizer? althought i would think it would have to come in thru the stat gear, i think the failure start point is probably at the stat gear, pix?

 

I used the original bearings as I read in Racing Beats manual that its best to keep the originals on higher mileage engines. The car ran smooth prior to rebuild so I can't see how rotor or stationary gear bearings could do damage, nor the housing.

Is it possible to index the rotor incorrectly? It seems impossible to place the rotor in wrong after the e-shaft is in.

Lapping plates makes the endplay tighter, and I can't recall the exact spec but it was with the FSM limits

Thanks for your suggestions guys, I'll take a look again (motor not at a friends shop) maybe I'll have a eureka moment.

 

Pictures, please.

 

I'm thinking the front stationary gear rotated somehow.