I'm beginning a rebuild on a S4 13B. I measured one of my brand new, pre-glued, mazda 2-piece apex seals last night - it's 3.1540" long.

Rotor housing width is 3.1490"

I'm a little surprised that new factory seals would be that much over https://www.nopistons.com/forums/pub..._DIR#>/dry.png

The FSM mentions nothing about this - though I gather from other sources (Judge Ito, mazda motorsports) that the apex seal must be clearanced to anywhere from .0015" to .0049" under the housing width (depending on source for info).



Anyone else out there have advice on clearance, whether this oversize length is normal, and best way to 'DIY' adjust it while keeping the end square?



thanks all

You need to figure in this...the corner part will snap loose and slide making the seal shorter. Also, the glue in there may be making it seem longer than it is.



GregW

the whole reason they have the corner bit is so it is self clearancing in length

Thanks guys - https://www.nopistons.com/forums/pub...IR#>/blush.png

First rebuild anxieties https://www.nopistons.com/forums/pub...IR#>/blink.png



It had looked to me like the mitre cut went right to the corner of the long piece, but it was late last night and my eyesight isn't what it used to be...........I'll have to have a closer look. I was worried if the short piece moved down along the mitre, the sharp corner of the long piece would score the side housing.



I suppose they glue them up oversize so the tightening down of the tension bolts on assembly will pop the glue joints?



Curtis

You will hear some very freaky snaps as you turn it over by hand the first time. https://www.nopistons.com/forums/pub...#>/biggrin.png



GregW

The H2MYRX7 book recommend race clearancing your apex seals down to 79.90mm. I did this to my apex seals, but it really did nothing for the engine. I probably don't make enough power to warrant such special attention. https://www.nopistons.com/forums/pub...IR#>/smile.png



Since then, I've just slapped the brand new Mazda OEM apex seals in all my customers cars with no problems. I had a talk with Mazdied about this, and bottom line is you get less damage from the triangle assist piece with the longer seal.





-Ted

also have to keep in mind that the cars in the h2myrx book are running for like 24hours at wot on carbon seals, you might not get the same growth in a street car.



be careful mazdized used his last motor to flatten bolts that should have been on his carb....

Did he also figure out a way to imprint pretty shapes into his rotor faces? https://www.nopistons.com/forums/pub...#>/biggrin.png

yep