Turbos to Downpipe Gasket
 

Hey Everyone,

Been a few years since I last posted or done anything with the 7, figured it was time to get going on it. I ordered a few parts from Banzai mid pipe and some braces. I figured if I am going to put a mid pipe in I would wrap the downpipe while I am in there anyway.
After breaking one of the studs I managed to get the downpipe off, I am guessing it is a SS HKS (always nice when there are good parts on the car)
Anyway once the DP was out I noticed that there were two gaskets on the turbo to DP connection, is that always the case? the gaskets are a laminated metal style looks like there are 4 thin sheets per gasket. There was no signs of leaking or anything and after reading some threads it sounds like I can reuse them, should I reuse both sets or just one?
My thoughts are there is only supposed to be one and that is what I should use but I would prefer some more experienced opinions on this.

Thank you

Mike

I believe the car came with just one, mine did. There could be a multitude of reasons the previous installer used two. Sorry to hear about the broken stud - that is a terrible thing to work on; one of the hardest jobs on the car in my opinion.

If it were me, I would reuse the one in the best condition, i.e. 4 total laminated sheets.

This is the stock gasket -

https://www.atkinsrotary.com/store/9...tegory_id=1234

It's VERY high quality and typically re-usable many times. Also it's stupid expensive.

My guess is there was an exhaust leak or something and someone tried to put 2 gaskets on to fix the problem. That can actually cause more of a problem since you increase failure points.

Exhaust gaskets on the FD should have 2 clean flat flanges with the gasket sandwiched in between - no gasket sealer, RTV, or anything like that. Exhaust should be tightened front to rear. If flanges aren't lining up right so they are flush with each other it could be a multitude of things from a bent exhaust hanger to shot engine mounts.

Good luck on the broken stud, that can be a BIG damn pain! May be worth just pulling the turbos to have more room to work on it but that's a whole project in itself.

Dale

I managed to get the stud out, used some heat and some KB88 on the hot stud. Once it cooled a little I used a stud removal tool, looks like a socket with three rollers inside. I had just enough room to get that socket on it as it was the lower front stud that broke.
The gaskets look just like the one from Atkins but there are two. The flanges look immaculate on both the car and the DP so I will try just using one and see how it goes.
Thank you Dale and Jarod

Well I think I found out why there were two gaskets on the car. The down pipe flange is cracked where it is welded to the pipe. I think they were thinking it was leaking from the gasket not realizing the weld is cracked. That is my going theory anyway. I painted the pipe with VHT primer before wrapping it and to also look for cracks hence the gray.
https://cimg2.ibsrv.net/gimg/www.rx7...2a0630f10c.jpg

Good find!

You should be able to find a welding shop that can re-weld that for you.

Before installing make sure to get all the paint off the flange and check that it's flat with no old junk or anything on it. Looks pretty good, just needs the paint cleaned off.

Dale

Going to the machine shop today to get a bung welded in and that flange re-welded. Yeah I will take some scotch brite to the mounting surface of both the pipe and turbos to make sure there is no gunk on them. Thanks Dale

Any reason why I should use the Mazda stud (9YA9-21-008) over a M10-1.5 x 40 mm stud? Thread pitch is the same .75mm shorter and $4 ea not $25. Unless there is something I am missing.

Thanks

People here will recommend stainless steel studs, some will recommend inconel. Don't use chromed or galvanized. Whatever bolt material you use, a high temp anti-sieze compound should be used, get a good coat on the threads. If you have a tap, I would chase the threads into the block before you put studs back in, just to prove to yourself that the threads are sound. The tap should turn with very little force except for minor hangups here and there.

I could have sworn I saw an "automotive stud" which very closeley resembled the studs that came with the car at Ace or maybe Home Depot. That could be an option. You could also do a WTB ad on the forum and I bet you could get some decent quality used ones if you're cautious about non-OEM.

First thing I did after I got the stud out was chase the bore lol. I am leaning towards automotive as I have some here, and thinking on it now this will be the last time I work with these turbos. Next time BNRs lol. Thank you for the confirmation j a r o d.

Mike

Well I think I know why the pipe was cracked and why someone used two gaskets on it instead of fixing it correctly. The flange has been seriously warped. After a few phone calls to some different machine shops in my area only one was willing to even look at it. So I explained the problem and was told I would be best off using a long hand file and elbow grease. Well after an hour of filing she is perfect, and yes I made sure that it is flat on all planes lol I will only need one gasket now :lol:

https://cimg4.ibsrv.net/gimg/www.rx7...0b9a40885f.jpg
Before filing

https://cimg7.ibsrv.net/gimg/www.rx7...0a291679d5.jpg
After Filing


Sorry for the pictures being so big, I can not get image re-sizer to work

https://cimg3.ibsrv.net/gimg/www.rx7...fda50f4ebd.jpg
After a few file strokes to identify high spots
https://cimg0.ibsrv.net/gimg/www.rx7...eaf9f15b1d.jpg
45 mins into filing

I was thinking I should knock the burrs off the inside of the pipe to help the gasket seal some more as there are a few good dings in there. Anyway I figured I would share what I have found.

Mike

Nice job!

Yeah, knock any little hot spots down. I would probably also sand the whole thing with a Scotchbrite so it has a uniform texture.

Are one of the existing gaskets re-usable or will you need a new (or good used) one?

Dale

Thanks!

The flange is all flat now and has an even finish (just finished with the purple scotch brite type pad) same with the manifold. Both of the old gaskets look good, I am going to go over them both with a fine toothed comb to find the best one. I ordered a new one not realizing how expensive they are lol oh well on the parts shelf for when I upgrade the twins lol. What do you think about running a file around the inside opening to remove the burrs? I am thinking that a light pass with the file shouldn't hurt but I wouldn't mind your input Dale.

Thanks

Penetrating oil like PB Blaster really helps with exhaust hardware. Spray a shot or two on the threads before turning any wrenches, and if the parts have been sitting for a long time it might help to spray a few hours ahead of time and then re-spray again when you start working.

Yeah I think a light pass to get the burrs would be fine.

Dale

I used KB88 from LPS which works very well, I have had a hard time finding PB in my area (small town northern BC). The problem with the one that broke was the collar on the top of the nut folded down into the threads, it must have got caught on a thread. Once it was folded down there is no going back lol, and not enough room to use a nut splitter in that area.