The first choice would be the square ring, but round will work fine. There are damn few round bottomed "O" ring grooves in this world.



If you have a junk housing, cut out a section with one cut beside a dowel hole. Place a piece of your proposed "O" ring in the grooves and clamp it up. This will get you an idea of alignment and volume.

So long as there is a bit of room left in the groove after torque up, it will be fine.



I add a tiny bead of silicone along the rotor side of the groove. Once the engine is torqued up, I turn it over a few times and clean out any excess silicone through the exhaust port.



The faces of the groove would have to be real close to mating, but I suspect that they are anyway. The irons are fairly weak where they cut that groove, so a hydrauliced ring would almost cirtainly break the iron.





Lynn E. Hanover

 

I can't tell you how I know, but suffice to say there is a 12A race car in the UK running FD secondaries. Now half a season of racing between teardowns vs whatever your MTBF requirements are may not stack up, but a pair of stock O-rings has been shown to hold in a sample of 1.

 

That sure would be the easiest. Thanks for the heads-up.

 

Look back in my PP build up posts.



I used DEVCON Liquid Steel B to fill in the grrooves on my S5 PP Housings. I had the housing lapped after that.