Firstfives.org

Hey folks. I'm letting my fantasies get ahad of my research, so here's an attempt to catch up.

Here's my situation: I live in CA and I have a nice normal 1980 528i. One day, I was kind of bored in my garage, so I took everything apart. I removed the engine, tranny...everything, basically. Ok, I was really bored. Then I went and got a 3.5 from an e34 (mechanical condition mostly unverified but looks good) and basically planned to drop it in and use L-Jet, stock exhaust, etc. Completely stock look, easy to pass smog, I would guess.

But I also have my own complete, very strong, very nice e34 535i, that for various reasons, I am now strongly considering cannibalizing (more boredom, perhaps?). I don't really think I want to use the Motronic but I would be interested in using the whole exhaust system, minus muffler (fitment issues). Could I do that, get a performance muffler, and still pass smog in CA? Could I bore one of my 3.5 engines into MM 3.7-type specs, use L-jet and the 3.5 exhaust system with performance muffler and *still* pass smog? What would I have to do?

And finally, just theoretically this time, since I unfortunately do not have an s38 lying around, could one install one of those with all the m5 injection and exhaust and pass smog?

Ok, educate me, please.

Thanks!
Ken
1980 528i (5-speed)
1991 535i (5-speed)
1980 MB 300TD (looking for 5-speed)

It gets complicated. Technically, it's supposed to be the original engine, or a "replacement" engine which is nominally the same, meaning a 2.8 E12 engine. Realistically, even a state BAR rep told me, "if it looks like a duck and quacks like a duck, it's a duck", meaning they don't usually go down to the serial number level if it looks original. In other words if you keep it L-jet you should be ok. Changing the exhaust will probably be ok, I've smogged a E23 733 with a 735 exhaust, which is kind of what you're talking about. Again, if it looks like original parts, you're probably ok. Headers no, later stock manifolds shouldn't raise a red flag. And you can put any engine in it as long as it's later and you go thru the referee process. But you need to do everything. Later evap and all more than likely. They usually go over it pretty carefully, but other times they let alot go by. You never know if they are going to be sticklers or not, but if you do everything right, it will pass with flying colors. As long as it passes tailpipe ok too. To the later standards. As far as boring it etc, if you don't tell them, they won't know, it's not like they pull the head to check the bore and stroke. As long as it looks stock, and passes tailpipe, you are probably ok.

Thanks, Mike! Excellent info.

Now, my next question would be--is the performance gain significant using the e34 exhaust (manifold and cat) over the e12 2.8 one? Or are we just talking about a pretty marginal difference? And what if I do bore it out to 3.7--would that change the answer? It seems like 3.7 would be too significant of a jump to allow using the 2.8 exhaust to work well, but that is just a gut feeling.

Finally, in an almost totally unrelated question, is it true that 530i's had vented rear discs?? If so, how hard is it to convert a 528i with solids? Need calipers and discs only? Or more?

Thanks,
Ken

I wouldn't expect to see any gain with a stock engine, they did use the same exhaust with 3.3s of the same era in 633/733s. And yeah, if you went up to 3.7, it probably would make a difference then.

Vented rear rotors were only used on 82 and earlier E24s, no E12s that I know of. I can't remember if you need to change the whole trailing arm, or just the rotor and caliper, seems like it's the whole thing but I can't recall for sure. Not worth it IMHO since it's the fronts that see most of the work.

you can put any muffler/ exhaust system you want, as long as it doesn't leak or delete any emissions equipment. you can also swap almost any engine you want into you car as long as it is 1) newer than the car its going into and 2) keeps all the emissions equipment that would be on the car that donated the engine. you just need to have your swap ref'd and smogged and your good to go.

great info, guys! the wheels in my head are in motion...

Ken