After breaking down one of my 12As and checking then double checking tolerances I found something that concerns me a little. One of the apex seal grooves in the rotor is worn a little awkwardly. It appears that the clearance between the rotor and the apex seal varies as I check from one side of the grrove to the other by less than 0.1mm but there is a difference. The one side is in spec but the other side is at the limit. This is the only apex seal groove to do this. I will be getting new apex seals (Rotary Aviation possibly) but this is clearly an issue with the rotor. Should I be concerned or will I be alright with new seals? If needed I can tear down my other 12A and spec out those rotors to see if they are better and if they are I can use the entire rotating assembly.

Thanks

 

I have seen this on a few 12A's that I have torn appart. Its something to do with the rubber cornor seal's wearing out and the apex seal flapping around in the rotor itself. I have a rotor that is completly inilated by one cornor seal that went out then it and distroyed the rotor housing, rotor, and mid section. To my knowledge of engins in general as long as you have a good seal even if its only .01 difference it will hold, but if you have lots of spare parts that would can build a good in spec engine I would go with that. No sense in building it twice know what I mean.

 

I'm going to check out the other engine. Ironically that seal ended up being fine except for .03 mm or so more side wear BUT there was another apex seal on the other rotor that cracked the last 10 mm off but the whole thing stayed in the groove and ran quite well (considering the leaking intake gasket on the weber). It just made a tiny (very insignificant) scratch on the housing but otherwise both housings are MINT (this engine was run on premix for its entire life). This engine was rebuilt by its former owner 50000 miles ago with new rotor housings and the rubber seal inserts were left out. The ONLY reason that I broke it down was that a tiny bit of coolant was seeping into the oil (because its not like I have any interest in porting or anything ;p) but I'm glad that I did because I found the broken seal plus the questionable rotor groove. My bearings are also SHOT. I do want everything to be in spec because this engine probably will see boost in the future with a goal of about 300 RWHP.