BMW E46 Fanatics Forum banner

21 - 29 of 29 Posts

·
Registered
Joined
·
1,173 Posts
Are you talking about the downpipe/cat to exhaust pipe connection, or the head-to-manifold connection?

The downpipe connection uses Inconel bolts and copper plated steel nuts. Do everything you can to avoid snapping the Inconel bolts. New bolts are $20+ each and you'll be spending that much for the drill bits to drill out the snapped one.

Inconel is OK to heat up to 1300F, somewhere between "blood red" and "dark cherry". That's the best way to remove a rusted on nut.

An exhaust shop that uses a "heat wrench" to make them glow orange will damage their grain structure. Not a problem for them, you are the one that will pay in the future. Similarly knocking out the bolt with a air hammer risks breaking the catalyst and oxygen sensors -- a future problem for you.

The only advice for the heat-to-manifold nuts is to let them soak for a day, and expect to replace a few studs. PB Blaster in a spray can is my favorite. It would be Aerokroil, but that stuff climbs up out of the can at night and dissolves the neighbor's robo-cats.

Always replace the copper-coated nuts. Using them strips away the copper coating, leaving exposed steel. I can get away with sometimes reusing them in dry parts of California, but re-used nuts will rust in a few weeks elsewhere.
What's great about acetylene is that it heats up the nut faster than the inconel. Shouldn't ever run into that problem.
 

·
Registered
Joined
·
24 Posts
Discussion Starter #22
Hello DBecker

thanks for the info about the Inconel studs in the downpipes. I didn't know those were a special metal. We didn't have any problems with separating the exhaust from the downpipe/cat/exaust manifold assemblies. I think that is because we'd just had that area apart when we did a AT to 6 speed MT swap last year. For that project we actually needed to make a custom length driveshaft. We used a donor shaft along with the 6 speed shaft and married them together at the correct length. It was my first effort at welding a driveshaft, and it turned out pretty good, with no vibration at speed.

We'll see how the header installation, and mating/fitting the "ebay" headers upto the OEM exhaust. I've read that can be a PIA. Again... time will tell.
 

·
Registered
'03 325iT Mystic Blau
Joined
·
2,207 Posts
Hello DBecker

thanks for the info about the Inconel studs in the downpipes. I didn't know those were a special metal. We didn't have any problems with separating the exhaust from the downpipe/cat/exaust manifold assemblies. I think that is because we'd just had that area apart when we did a AT to 6 speed MT swap last year. For that project we actually needed to make a custom length driveshaft. We used a donor shaft along with the 6 speed shaft and married them together at the correct length. It was my first effort at welding a driveshaft, and it turned out pretty good, with no vibration at speed.

We'll see how the header installation, and mating/fitting the "ebay" headers upto the OEM exhaust. I've read that can be a PIA. Again... time will tell.
Holy crap are you lucky as hell!

I've been a professional welder for more than 25 years and I'd never tackle something like that because of the importance of balancing the assembly.

BTW, most people either swap the diff or use the input flange from the 6MT car's diff rather than making a custom driveline for this swap.
 

·
Registered
Joined
·
24 Posts
Discussion Starter #24
Luck may have played a part... but I labored over the decision for weeks. In the end it was worth trying, and with diligence it worked out. I intentionally made the weld as close to the shaft end as possible for the reasons you mentioned.
Mechanically it seemed like the closer to the end would minimize any out of balance condition. I focused closely on making the weld as consistent as possible. There was a bit of grinding off heavy areas, but that was only a small need. I am also glad it worked out. If this car were a 400hp monster, I wouldn't have considered it, and the solution you detailed would have been our next move.
 

·
Registered
Joined
·
24 Posts
Discussion Starter #25
Sorry to all for the late update. Our parts did not arrive yet (new copper 7mm x 1.0 exhaust nuts and the new motor mount from FCPEURO). The website indicated any order placed before 2pm ET would ship that same day... BUT that did not happen, instead because I choose "economy ship" that is the lowest priority order and so they decided to push it off til the next day. I called and that is what I was told, even though the website is very specific. When I called by phone, they did offer me an account credit to offset the inconvenience, but honestly I'd have preferred the parts to arrive yesterday, or at the worst... today. I intend to update this thread once the catless header system is installed, hopefully with no more drama. I will advise! THX to all again.
 

·
Registered
Joined
·
5,901 Posts
I used FCPs economy shipping on a small gear, I missed the shipping deadline and figured it would come USPS. They drop shipped it and is coming from N Carolina via UPS. Ordered on Thursday, will be here Monday morning. I'm in Wi too.
 

·
Registered
Joined
·
24 Posts
Discussion Starter #27
OK the headers are installed. Economy SS Ebay headers for $100. The bolted up fine on the motor, but we needed to add about .3" to one of the downpipes to match the OE exhaust. No problem. Sound it basically the same. Ian did notice a power increase, but I have not driven the car. HOWEVER, it is still not performing up to its standard for sure. I think we need some more experienced help. I can do the wrenching, but need a hand at accurate diagnostics. Hoping to find a source in the Milwaukee / Chicagoland area. I just don't know what to do next.

A few things of note... car does go thru oil, but I don't believe it has low compression. Seems to have something to do with the CCV system. We did replace all those components along with the intake manifold gaskets last year. The rubber intake boot was replaced at that time too. Just did a valve cover gasket. Trying to eliminate vaccuum leak possibilities. It may well have to do the the computer though. We switched out the automatic for a 6 speed MT last year, and the dash was lit like a Christmas tree. I will start a new thread.

Thanks to all for the help on this part of our E46 saga!
 

·
Registered
Joined
·
203 Posts
OK the headers are installed. Economy SS Ebay headers for $100. The bolted up fine on the motor, but we needed to add about .3" to one of the downpipes to match the OE exhaust. No problem. Sound it basically the same. Ian did notice a power increase, but I have not driven the car. HOWEVER, it is still not performing up to its standard for sure. I think we need some more experienced help. I can do the wrenching, but need a hand at accurate diagnostics. Hoping to find a source in the Milwaukee / Chicagoland area. I just don't know what to do next.

A few things of note... car does go thru oil, but I don't believe it has low compression. Seems to have something to do with the CCV system. We did replace all those components along with the intake manifold gaskets last year. The rubber intake boot was replaced at that time too. Just did a valve cover gasket. Trying to eliminate vaccuum leak possibilities. It may well have to do the the computer though. We switched out the automatic for a 6 speed MT last year, and the dash was lit like a Christmas tree. I will start a new thread.

Thanks to all for the help on this part of our E46 saga!

Sounds good, the better performance probably comes from the lack of a clogged exhaust.

The rest would probably be a vacuum leak or, as you mentioned, low compression, I would do a smoke test and compression test all around and see what you find.
 

·
Registered
Joined
·
2,915 Posts
For anyone in salt belt, the only thing that works on these is heat and beat. Nothing else helps.

Last weekend buddy and I spent literally an hour trying to separate exhaust from manifolds on e90. We have torches, air tools and the lift. Just shows how much PITA this job can be
 
21 - 29 of 29 Posts
Top