I had a 74 BMW bavaria with the 3 liter six. The original distributor had an advance and a retard feature which kicked in when cruising on highway. The performance was clearly choked off. I had a couple of older distributors around off mercedes and VW and mixed and matched weights and springs so that it performed like a non smogger. The difference was truly amazing. I also had to open the holes in the distributor plate to allow more movement. It was well worth the effort.

I also bought a euro only four barrel intake manifold for the car and installed it with a quadrajet which was jetted like it had been for the pontiac sprint ohc motor. With the all mechanical secondaries you had to be careful not to open the throttle until about 3000 rpm or it would bog down.

Fitting the manifold required some juggling of motor mounts and grinding material off the manifold to clear the power brake booster.

It was a lot of work but I was young and full of energy.

I imagine you can find a distributor which will interchange without too much trouble which has pre smog performance.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.