Just went out and checked a couple things, I've got good spark at both rotors, when I pull both wires off the back rotor it runs the same, when I pull both wires off the front rotor I don't get anything at all, not even a pop out of the tailpipe (it's only running on the front rotor). As I said before, I've got good oil pressure and the temp is good.

I was reading somewhere on this forum that there is a valve on this engine that shuts the back rotor off when the vehicle is decelerating, could that have caused this?


If someone knows where this valve is on the engine, maybe I could try disconnecting it...

 

have you done a compression test?

 

Not yet, have to get a tester.

What should the compression be?

 

Just pull the plug and listen or put your finger over the hole. A bad rotor will not give enough pressure to push your finger off.



So give you car the finger.

 

Ok, I'll go check that right now, can a rotor go bad that fast? The power loss was pretty much instantaneous.

 

Yea It can happen real fast. I was going down the road and the car went to shurdding and that was it.

 

yep a apex seal can go and there went 1/3 of the motors power(combustionable area) it can still run just poorly. i drove my 81 over 100 miles when i lost the rear rotor....
remove the lower plug from 1 rotor and kill the spark to the motor and spin it over it should do 3 swooshs at even intervals and they should sound pretty close to the same ... install plug and do the other rotor the same way.

 

I did the top plug on the rear rotor and there was nothing at all.

How hard is it to rebuild one of these? Can I replace just the seals on the rotor, or will I have to go through the whole thing?

Thanks for the responses.

 

that sucks man.. worst case, if you blew a apex seal.. your not going to be able to just take the front plate off, put a new seal in, put it back together, and go on your way. youll probably have to get a rebuild kit (pretty pricey) and if you ate an apex seal, your looking at a new rotor housing, and probably a new rotor as well. is it a 12a? your best bet would probably be to find another one out another car, or it someone is selling one, unless you have the time/money to rebuild it yourself. goodluck man

 

yea its a full rebuild. if your lucky you will need a rebuild kit( gaskets and such) and new apex seals. most likly you killed a rotor and housing. i think 12a housings are around 600 NEW but you should beable to get a good used 1 cheap. if you ate up the rotor you need a matching year /motor rotor and if it was me i would have the rotating asmbly rebalanced to make sure it was all good and right. otherwise the rotors will shake like hell and eat up the motor in no time.

 

I know the feeling I just had 2 apex seals for breakfast a couple of days ago. The rebuild costs far exceed the need to rebuild a 12A so I am building the monster 13B instead.

 

Found a wrecking yard nearby that has a few 7s, the guy there said his books showed 82-85 had the same engines, will a rotor and housing from one of these work? Also, are the front and rear rotors and housings interchangeable?

The guy at the wrecking yard said he'd sell the motor out of one for $200, he said he doesn't know what kind of shape though.

 

from everything I have read, you can't use a front rotor in the rear and vice versa.

All 82-85 12a engines are the same, so they'll work.

Don't be surprised if one of his cars is a GSL-SE with the 13b though.

Junkyards don't know anything about these cars.

 

Your best bet may be to just use the junkyard motor. See if its turns freely by hand.