I've posted a couple of times about this and I've done a lot of searching. Most of the posts seem to quote from the same article that makes removing the old manifolds sound very easy. I thought I'd post how I got on and what problems i'm facing for anyone else that wants to try this.
My car is a 1998 323i coupe with aircon - there is no secondary air pump etc attached to the manifolds on this model. I've already removed the backbox and center section which was fairly straight forward so I'll skip this part.
Today I removed the M52 manifolds. Cracking the nuts off was the easy part, soaked them in penetrant and set about them with an 11mm flat edge socket. I worked from above and removed the front bank nuts first. All of the studs came out with the nuts. For what its worth, I was able to do this without the use of flexy joints etc, only straight sockets were used, despite having the flexy's available, I found them more of a hinderance than a help.
Once the nuts were off however, I was unable to withdraw the manifold due to space within the bay - the connecting arm to the steering rack being the main culprit. I then removed the rear bank nuts, again, 11 of the 12 studs came with the nuts, the rear manifold was easy to remove once freed from the cylinder head.
Then came the most frustrating part of the day, all the nuts were off, both manifolds were separated from the head, but I found it VERY difficult to remove the longer front bank from its bavarian prison. In the end, I removed the o2 sensor with the manifold in position and withdrew the manifold from the topside by squeezing it past the aircon pipes.
Here you can see the old manifolds on the right and the M3 evo manifolds on the left.
Now, my questions are as follows..
How in the name of all the is holy are these going to fit back in? They appear longer and wider than the standard manifolds that were a tight squeeze in the engine bay.
Will I have to remove the connecting arm from the steering rack? Doing so should give me a lot more room to manouvre. - It looks like it is secured with 13mm nuts with knuckles at both the steering wheel end and the rack end? Simple as that?
With regards to the exhaust itself, the M3 exhaust is considerably heavier duty in every respect than the standard m52 system. I will weigh them for comparison, but the backbox alone must weigh double that of the 323 box.