AlwaysBroken

I took off all my turbo/exhaust stuff to switch to inconel and stage 8 fasteners while I'm changing out the steering rack.

My turbo exhaust manifold flange isn't perfectly flat. Eyeballing it with a straight edge, I'd say the middle part is about a millimeter closer to the head than the ends. The flange is basically a nice thick slab of steel. It's one of the old JGS ones.

Option A: slather everything in ultra copper and pray it holds. IIRC this has worked ok in the past, but my car has a long history of nuts coming loose so my recollection is hazy
Option B: machine the manifold flat where it mates with the head, add ultra copper, torque down with lock nuts, never **** with it again

I've pretty much decided that I'm going to do option B, but I'm worried that the manifold surface on the nut side won't be perfectly perpendicular to the angle of the studs coming out of the head. Is this cause for concern at all? My gut says probably not, just wanted to be sure.

Art

.

DNMakinson

iTrader: (3)

I am understanding that you are talking about the manifold flange that mates with the head. Yes, mill or sand flat. Yes, use a MLS gasket such as OEM. Yes, torque to Mazda specification (38-42 ft-lbs). I don't recall a specified sequence. Mate it dry is fine. I like to use Nickel based antiseize on the nuts.

AlwaysBroken

My worry was that since the flange is slightly curved, machining the head side flat will leave the nut side slightly curved, which means the nuts/washers will be engaging at the slight angle. I figure it's probably not a big deal, just wanted to hear a second opinion.

Do you guys really think the metal OEM exhaust gasket is better than RTV?

Also, I wasn't going to bother with multiple heat cycles and retorquings since I'm switching over to the Stage 8 kit. I figure I'll be OK with just ARP thread lube and a torque wrench. Dunno how sound this logic is, but I think with all the locking tabs I should be OK.

90civichhb

iTrader: (5)

I had something similar happen with my manifold as well. It's an old used manifold from ARTech. I cut a few extra relief cuts in the manifold, had it milled, and then finished it off on a belt sander. I also used a MLS gasket with copper silicone. I have about 2k miles; dedicated autocross car so they are pretty hard miles, and it hasn't shown leaks. I will have my first track day in the car on Monday which will be a good test for the method.

airbrush1

I had my old manifold milled flat atvthe machine shop due to a similar issue. It won't cause you any problems to do so

Art

.

AlwaysBroken

The ultra copper stuff lasts pretty much forever. It's basically just high temperature orange rubber. I've used it as an exhaust gasket replacement in the past. As far as I can remember, it works great, even at high boost levels.

As for maintenance, yeah I get that. I just want to get away from the "retorque once a week" bullshit that I got used to previously.

BTW, I'm not just swapping out the mani/turbo fasteners, I'm doing everything. The manifold/head fasteners are moving to stage 8 locking nuts on stock studs, the mani/turbo interface gets the TSE inconel kit and I've converted my turbo/downpipe fastners from bolts to studs so they don't seize up anymore (well they probably will seize up, but I won't give a ****).

Bronson M

iTrader: (1)

Guys the ultra copper is rated to 700 deg, exhaust temps are in the 1300 degree range....... It's just a matter of time before it burns out. Use a factory MLS gasket and move on with life. If you're worried about the warped flange bolt it up without a gasket and see what feeler guage you can slip in. Betcha quite a bit if it comes out once it's torqued. I can tell you my turbo outlet had .004" warp and still sealed with a MLS.