2MM or 3MM
 

Plan on building my 13B BP.So i'm throwning this question out there. what do guys think?

there is really no reason to run the 3mm seals unless your rotors are out of spec. ESPECIALLY in regards to naturally asspirated engines.

i have a set of 85 13b 3mm rotors that are almost new and a set of 2 mm rotor, so your telling me to go with the 2mm. why? some input please. thanks

What year are the housings you're using? According to Racing Beat, the later 2mm rotors can't be used in '85 and earlier housings and vice-versa because of "geometry and compression ratio differences".

i wasnt aware you already had a nice set of 3mm rotors, otherwise i would say roll with that for budget reasons. But as a whole a 2mm seal has more development and more options along with less surface area meaning less friction.

2mm seals better at high RPM (meaning less chatter and less rotor housing wear). 3mm is stronger, but I can't see that ever being an issue for an NA engine (or a turbo engine that's been tuned properly, for that matter). In my mind the ONLY reason to use steel 3mm over 2mm is for cost savings: if your rotors are out of spec, you can have them milled for 3mm seals and reuse 'em. Carbon seals are lighter, so it's less of an issue if you're planning on using those, but the 2mm rotors are lighter, so I'd still use the 2mm ones.

Romulan_7: RB says that? That's BS, they work just fine in pre-'86 housings.

I'll keep that in mind if I'm ever putting together a 13B.

2mm apex seals seal better, so you have potential to make more power with them

well i guess there goes that theory LOL