Worth swapping to OBD-II exhaust manifolds?

[marek|steezkal]

Been meaning to snap a couple pics and finally got around to it.

Clearance between E34 cast manifold (front) and motor mount arm. I'm thinking this is too close. Back side is touching the heat shield and there is no way the top left bolt on the motor mount is accessible.

Looks like I will be looking for some OBDII manifolds to buy.

[LTDScott]

Plenty of clearance to the engine arm.

[LTDScott]

Yes, E34 cast manifolds. I'm planning on making my own 3-hole down pipe flanges out of 3/8" or 5/16" steel plates and welding them to my down pipes that I will modify.

I was just worried that one or both of the manifolds wouldn't clear the subframe, sway bar, and/or the control arm bushing.


Edit: Did your front E34 manifold come REALLY close to contacting the E36 engine mount arm? Mine is maybe 1 mm away from the heat shield that goes over the mount arm. I'm hoping that won't be too much of an issue with heat.

As you can see by my photos, the E34 and E36 manifolds are overall the same shape/dimensions with the exception of the "clocking" of the bottom flange. All clearance issues would be the same as the E36 manifolds (which is why I'm using the washers to lift the engine slightly so the exhaust clears the subframe). There's no clearance issues to the engine arm at all. I'll take a photo after work.

[King Mufasa]

sorry to go off topic

Make them 6-2-1 Maserati does that on their v12's for a reason..

this is VW's I always wondered what it would yield on a str6 BMW

[marek|steezkal]

Yes, E34 cast manifolds. I'm planning on making my own 3-hole down pipe flanges out of 3/8" or 5/16" steel plates and welding them to my down pipes that I will modify.

I was just worried that one or both of the manifolds wouldn't clear the subframe, sway bar, and/or the control arm bushing.


Edit: Did your front E34 manifold come REALLY close to contacting the E36 engine mount arm? Mine is maybe 1 mm away from the heat shield that goes over the mount arm. I'm hoping that won't be too much of an issue with heat.

[LTDScott]

Bummer, I was hoping to keep the cast manifolds because I cannot stand the raspy tinny sound of tubed manifolds. At least the ebay tubed manifolds sound awful.

If adding a small spacer under the mounts doesn't help enough, I'll be looking for some OBDII mani's.

I'm not sure what you're trying to get at, but yes, the E34 M50/M52 manifolds will bolt onto an E36 M50/M52 engine, except that the flange for the down pipe is different between the E34 and E36. Seems like you have cast manifolds from an E34? If so, you could just have a muffler shop modify the flange on the down pipe (if it was sourced from an E36). That's what I'm electing to do.

FWIW I have three flat washers under my engine mounts to raise up the engine slightly.

[marek|steezkal]

Bummer, I was hoping to keep the cast manifolds because I cannot stand the raspy tinny sound of tubed manifolds. At least the ebay tubed manifolds sound awful.

If adding a small spacer under the mounts doesn't help enough, I'll be looking for some OBDII mani's.

[Nick_S]

I ran into this issue with E34 manifolds. The front header is at a slightly different angle than an E36. The rear is the same.

[marek|steezkal]

So the E34 manifolds fit in a 24V E30?

[LTDScott]

Well I bought some OBD2 manifolds, got the secondary air injection holes welded, bolted them on the car, and found the angle of the bottom flange on the front manifold that meets the downpipe is wrong. After a lot of cursing and research, I discovered that the previous owner of the engine (it has been in 3 other cars before mine) used E34 manifolds, not E36 :(



I would have just said screw it and re-installed the original manifolds, but I don't have gaskets for it. So now I have to decide what to do. The easiest thing is to just reuse the old ones, but I could install the new ones and have the flange on the downpipe modified to E36-style by a muffler shop. Or I could just abandon all of it and get some eBay longtubes, but that will require a trip to the muffler shop too. That wouldn't be so bad except the car isn't street legal and needs to be towed :(

[LTDScott]

Thanks for the responses. The impression I'm getting is that they should be a direct replacement for the cast iron manifolds minus the plugging of the air pump and O2 sensor ports.

Part of my motivation to use the later manifolds is weight saving, but I hoped there may be a performance improvement. That said, even if there isn't the fact that they used them on the M3 is a good sign. I'll start looking for a cheap set.

[Wanganstyle]

Nobody?

our e30 lemons has been been running OBD2 exhaust manifolds since the 24v engine install.

our headers are 100% unmodified m52b28 besides welding up the air injection ports;

a little weight savings is the main difference; no idea about flow; we didn't have any M50 cast iron headers to compare with.

[pandaboo911]

They are tubular and much lighter. The ports on the obd2 manifold are actually smaller but since the obd2 midpipe flows much better they are an upgrade.

[dynoclimb]

I did this a couple of months ago, unbolted everything, pulled out the cast OBD I's and threw in the OBD II's and bolted everything back up. No issues.
They are much lighter, and probably flow better. I haven't really noticed a performance difference, but it does sound different.

[LTDScott]

Nobody?