Ticking from rear rotor housing
 

I have a ticking noise coming from my rear rotor housing on 12a. I've read through various threads and several people suggest that either the spark plug wires aren't properly seated or that there is an exhaust leak. I've ruled those two things out. Here's what I've done.

1. I used the old school mechanics stethoscope (read: wooden dowel placed on various parts of the engine and against my ear). The ticking is without a doubt coming from the rear housing and it's loudest down by the leading (lower) spark plug. I used this method to thoroughly check all other parts of the engine and it's definitely loudest at that location.
2. I ran the car in a dark garage and there is NO arcing.
3. I removed the wires to each spark plug one at a time on the rear housing and ticking continued and did not abate.
4. I then removed both wires and got the same result
5. I ran the engine and got it to operating temperature and then did a compression check (fuel pump fuse removed, with helper holding gas pedal to floor and with both coils detached). All faces of the rotor appear to be about 95-105 lbs.

What could be causing this ticking? This car is new to me and it's possible that the ticking has been there all along, but I didn't start noticing it until very recently. The car runs super strong and does not appear to have any loss of power.

Is this normal? I'm running an autocross event tomorrow, but I'm wondering if maybe I should cancel.

Cracked rotor housing?
Notice any coolant loss??

Nope, no coolant loss. I flushed the coolant about 3-400 miles ago and the rad is still completely full.

Well I'm just kinda guessing bud. I'm not sure what the symptoms of a cracked housing would be?
I've heard of cracks forming around the leading plug... Someone else might know if they chime in.

My other guess would be flaking chrome in your housing.
Mine had a weird tick to it, and I figured it was something caught in the pressure plate. Turned out my rotor housing was shot! The ticking was the Apex seal catching the edge.

Try opening the oil filler cap while running. If you see a single smoke pulse that corresponds to the click it might be a broken side seal.
Barry Bordes

I have to agree with that.
As I mentioned I had a tick to. My son, and I stripped down my rotors yesterday. There was a broken side seal. Thankfully it didn't damage the housing.
Though there's some minor scuffing by the port.

Would be worth looking into so you didn't damage the housing..

No puff of smoke when the ticking occurs. I did notice today that it doesn't tick when I first start the car. So for some reason the tick goes away when the engine is cold.