I'm looking for a set of exhaust manifold nuts for my E30 M20 (manifold to pipe flanges). These are thin-walled M10 coarse thread nuts that appear to have oval locking collars. Overall width is around 13mm.

I've ordered "copper E30 exhaust manifold nuts" from Pelican Parts and (if I recall correctly) Bavarian Auto. Both sent nuts that were way too small. I've tried McMaster-Carr and some lesser web sites, but they don't have M10 nuts that are this narrow (standard M10's are 17mm wide).

I don't think there is anything special about the exhaust manifold studs on this particular motor. I suppose I could check with the dealer, but I'm surprised I'm getting the wrong parts from otherwise reliable sources.

Any ideas or should I just go to the source?