I've been using Grimmspeed gaskets for a few years on my Forester XT, and now my BRZ.

Very happy with them, a few of them have been in use the entire life of the current motor with no issue, and will be replaced with fresh grimmspeed gaskets when I do the next motor.

Have you tried loosening the head to header, header to OP, OP to FP, FP to CB, and then gradually tightening them all back down in small increments? More often than not that will work, and if it doesn't I really wouldnt be surprised if you have a warped flange at your OP/FP connection.

Nah, I dont think that we do. I've never touched the Perrin part you're talking about, so I have no idea. Our hybrid 2.25/2.5in gasket is designed to fit the subaru specific bolt pattern, as most parts do. The ID of our gasket is 2.48in. So assuming the perrin part has an ID of 2.55in, our gasket would sit inside that ID by .035in, which will seal the fire ring. If you're alignment is off though, and the edge of the fire ring were to completely overlap the ID of the flange it will leak.

So there is a couple things to try and to look out for. But I bet you'll get it.

Yeah seriously they are the only gaskets I've ever used in my life that I've been able to reuse several times over. And when we do R&D here we'll have a car apart and put back together so many times (way more than what any average person would do), and I can get away with reusing them so many times it's ridiculous. Plus, being stainless steel greatly increases their longevity.

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