Dedicated Exhaust Discussion

[moatilliatta]

If the exhaust wont slide back an inch minimum you don't have enough room for thermal growth.

Kinda like that muffler hanger on the car Garage Welt posted. That'll totally fatigue and break put through some proper paces.

Along with flexy on one side and non flex on a dual exhaust system, to much strain on the non flexy side, till fatigue and crack.. IE a lot of E30 down pipes.

[Striker01]

i like the good old flange myself, but IMO you dont want the connection too far downstream from the bell housing otherwise its a headers off job to remove the gearbox.

I would also think about whether adding studs might make it more difficult as you need to the clear the studs to drop it down. it depends on the layout overall

I would love to have the connection closer to the front but that would require significant changes to the rear bank, forward of the collector. That's not something I want to take on. I think I can still get the transmission off, it will be tight though.

[Striker01]

If the exhaust wont slide back an inch minimum you don't have enough room for thermal growth.

Kinda like that muffler hanger on the car Garage Welt posted. That'll totally fatigue and break put through some proper paces.

Along with flexy on one side and non flex on a dual exhaust system, to much strain on the non flexy side, till fatigue and crack.. IE a lot of E30 down pipes.

I'm don't think I follow what you're saying. I'm not familiar with the post you're talking about. I also don't see any way the exhaust can move an inch, I don't think the stock transmission hanger has the ability to move that much and the 30 some year old M20 mid section I took off is still in great shape.

[digger]

I'm don't think I follow what you're saying. I'm not familiar with the post you're talking about. I also don't see any way the exhaust can move an inch, I don't think the stock transmission hanger has the ability to move that much and the 30 some year old M20 mid section I took off is still in great shape.

He’s talking about when disconnecting the exhaust to get it off the stud and that there should already be plenty of play once gearbox mount is removed .Thinking more about it corrosion is probably not your long term friend and a bolt is easier to replace. Each to their own

[Striker01]

Hopefully my last post about these AA look-a-like headers. I'm going to call them sorted and send them out for ceramic coating.

Thanks to digger for talking about gearbox clearance, that's something I wasn't even thinking about and got lucky by just needing a slight modification for them to clear.

In this picture you can see the countersunk holes for the flange nuts. Unfortunately the holes aren't cut very precise and some of the studs weren't centered in all of them. Also the copper flange nuts are too big to fit into the ones that are centered, maybe 1/32" too small. I didn't like how some of the nuts didn't have much material to clamp on so I decided to fill the the countersunk area.



Filled, then lots of grinding and drilling.



I forgot to take a picture after grinding and drilling but here they are mounted, with the proper nuts.



This gap was at least an inch before I decided to shorten the primaries at the flange. It's fairly close now but both headers feel pretty solid and hopefully won't rattle together.



I got lucky here, I hadn't even considered removing the transmission. Just had to cut this little ear off (circled) and it will slide into place with the headers on. I also ran the grinder between the flanges, they were touching after the final welding.

[Striker01]

Mounted for hopefully the final time!

[Striker01]

Exhaust is sorted and on the car for good. Was wanting dual all the way back with an X-pipe but the magnaflow cat I ordered is 2 in/2 out single chamber. I'd already put a ton of work into the x-pipe so it stayed even though it's probably totally unnecessary. Gives a good place for both pipes to reconnect before the transmission brace. The M20 transmission brace mounted right up to the 17 transmission and I cut the tab off the old cat to put on my new one.

I mocked this up with the CAT heat shield jacked up against the car, cut the heat shield off after final welding and it left a nice gap for movement.



Here it is mated to the Stromung M20 muffler. I was hoping to leave the muffler unmodified but couldn't get it to work, ended up cutting off the flanges and using slip joints.



Midpipe is ceramic coated and mounted. Lowest exhaust point is where is passes under the rear axle, I'm happy with it. The CAB heat shield isn't touching, just the pic angle.



One of my header flanged warped during welding and was leaking. Found these gaskets, they seem to be great, no leaks when I fired it up yesterday. Sorry no pic before I installed them.





Short video of it running. In a garage with no load but at least give you an idea. No making fun of my slides, was deep cleaning the interior before putting seats back in and didn't want to wear shoes in the car. LOL

https://youtu.be/IDCbeZnhtVE