I did a bunch of research on apex seals and i've basically decided to stick with the stock 3 piece 2mm seals too... although ceramics have their benefits they only come in 2 or 1 piece so they don't seal as well as the 3 piece.... although it would be nice to not have any seal float > 8500rpm.

here you can see where I started on the exhaust ports.The stock is on the left.



https://www.nopistons.com/forums/upl...1035560505.jpg

Wholy ****.. damn I was in Guam for the last 4 days so I missed all this...



I've always used stock apex seals, but we're trying Atkins 2mm seaks in Igy's car right now and they seem to be kicking ass.. I plan on using them in my engines in the future... Here is some good reading on porting...



****, why can't I add a attachment..

Try not to go too high with the exhaust port Dave since it will increase overlap.

I have been told that the atkins seals dont seal as well. What kind of compression numbers are you guys getting. Nice to see you back. I was begining to feel like the only guy left here with a FD.

with stock mazda seals my FD engine has 150 psi compression....

Are you sure it's not 130 PSI? 150 is quite a bit more than stock.

150.... on both rebuilds.... everything is NEW.... those were not even with the engine broken in!



i saw another engine he did in the car... tested it..... 150psi... a 91 TII bridgeport engine for MPH Datsun race car

150 psi!!!!! WTF? 131 is about where everyone wants to have their engine 131 psi = 9 kg/cm2 and that's some REALLY good compression. https://www.nopistons.com/forums/pub...IR#>/boink.gif

I will bring this back up just to explain what people mean when they say "you don't want to much over lap" Ok see where the groove in the face of the plate is that is labeled corner seal track. See how it just barely grazes by the top left corner of the port. If that port is made too large and the over lap of port and rotor is to big the corner seal will get sucked into the intake port and boom .. bye bye engine.



I was asked this the other day by a forum member and I had to ask someone myself to make suer I got it right. Makes perfect sense to me now and hopefully you too.



https://www.nopistons.com/forums/upl...1035436272.jpg