Why Apex Seals Fail

Barry Bordes · 10-10-2009, 09:12 PM

So you can try a little experiment to test this hypothesis. Install a .0015” feeler gauge at the center of the apex seal simulating the raised spark plug area. The seal will be rocked-over .003“ and the wedge will put pressure on the pointed end of the apex seal. Note the exaggerated condition depicted at the top of the picture.

But we still haven’t gotten to the root cause. The real problem is the raised spark plug area on the housing. There are at least three approaches to this problem:

(1)- Use cold heat range plugs like NGK R7420-10 or 10.5. (This is easiest part of the solution.)

(2)-The harder second part is to cool the housing better.
A better pump is a good start. Second gen. cast impeller type pumps are a lot better or the Remedy pump for 3rd gens.

(3)-The most difficult part would be to port the housing in the spark plug area to minimize distortion.

But what is the best way?
The factory racing peripheral housing have a trough cast into the inner water jacket in this area but the are for NA applications.

Notice that the thru-bolt bosses have been severed.

10-10-2009, 09:12 PM	#2
Barry Bordes Rotary Fanatic Join Date: Feb 2008 Location: Slidell, LA Posts: 191 Rep Power: 18	So you can try a little experiment to test this hypothesis. Install a .0015” feeler gauge at the center of the apex seal simulating the raised spark plug area. The seal will be rocked-over .003“ and the wedge will put pressure on the pointed end of the apex seal. Note the exaggerated condition depicted at the top of the picture. But we still haven’t gotten to the root cause. The real problem is the raised spark plug area on the housing. There are at least three approaches to this problem: (1)- Use cold heat range plugs like NGK R7420-10 or 10.5. (This is easiest part of the solution.) (2)-The harder second part is to cool the housing better. A better pump is a good start. Second gen. cast impeller type pumps are a lot better or the Remedy pump for 3rd gens. (3)-The most difficult part would be to port the housing in the spark plug area to minimize distortion. But what is the best way? The factory racing peripheral housing have a trough cast into the inner water jacket in this area but the are for NA applications. Notice that the thru-bolt bosses have been severed.