I measured two new 3-piece apex seals and they were 80.10mm long. My rotor housings narrowest points are 80.0020mm and 80.0049mm. The How to Modify your RX7 book says to sand the apex seals down to 79.90mm length for street use. Some people don't clearance the length of new Mazda seals and say they're fine as new. Other people say to clearance it 0.0015" narrower than rotor housing width. And others still say clearance it 0.004" to 0.0045" narrower than rotor housing width. Who is right?

The triangle piece is super glued to the upper piece. Should I super glue the lower piece to the rest of the apex seal, to make it all into a one piece? So I can sand it all as one piece and get a uniform cut on the apex seal? How thick is the super glue between the top piece and the triangle piece, should I subtract that out when computing the length?

Also, I assume I don't sand the triangle piece. Just sand the other end(s).

Background: rebuilding a motor for the REPU. New 84-85 GSL-SE rotor housings, new S5 rotors, new 3 piece apex seals. 4 port Streetport, 3b end plates, 12a intermediate plate, weekend driver + some autocrosses.

 

I have never filed down any apex seals. I also don't like three piece seals, they just don't like to last as long as the two piece.

 

The triangle piece on '76 and later apex seals is supposed to self adjust for length so you don't have to. I'd only worry about apex seal length on one piece carbon seals and '74-'75 which had a triangle piece that sat below the main apex seal.

 

When the triangle moves down to shorten the overall apex seal length, wouldn't that reduce compression?

Why do some people say not to clearance the length, and others say you have to? Including Ito? How To Modify Your Rx7 book says to sand them down to 79.90mm for street use....................

 

the how to modifiy book is NOT talking about the 3 piece 13b seals.

the length of the multi piece seals are self clearanceing, via the triangle.

 

So just install them as-is? The triangle will move .1mm out of the way?

Is that why there's no mention of measuring apex seal length in the FSM?

 

yes they are self adjusting, but i have had better resuilts in compression by glueing the triangle and then sanding length of apex to same length as housings.... next engine (current one) i used one peice carbon apex so had to set clearance