Carbureted 89 M30?

Mike Goble

Mike Goble

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I'm going out to look at an 89 735i with the intent of securing the engine to replace the 3.0 in my 72 Bav that is starting to use oil. I will be gathering all the components necessary to run the engine, but I really like carburetors. Is it possible to adapt the Webers from my 3.0 engine to the M30B35 model?
 
In a word - yes.

This was my 3.5l twin weber 38/38 downdraft recently converted to FEI. The block is mid 80's 535i and the head a late 80's spanish casting.

P1010026.jpg
 
Sure. The main thing you need to is to convert the old engine to the old-style distributor, which can be accomplished by swapping some covers from the old engine over and using the cam conversion nut.
 
x_atlas0 said:
Sure. The main thing you need to is to convert the old engine to the old-style distributor, which can be accomplished by swapping some covers from the old engine over and using the cam conversion nut.
Click to expand...

How and/or where do I get a cam conversion nut?
 
decoupe said:
In a word - yes.

This was my 3.5l twin weber 38/38 downdraft recently converted to FEI. The block is mid 80's 535i and the head a late 80's spanish casting.
Click to expand...

Not to hijack a thread, but how did you like the 38/38's? I have a set that I'm going to put on my '69 2800cs and was thinking that was the way to go.

Dan
 
38/38 Weber

dang said:
Not to hijack a thread, but how did you like the 38/38's? I have a set that I'm going to put on my '69 2800cs and was thinking that was the way to go.

Dan
Click to expand...

Dan:

They came on the car so I really have nothing to compare them to but they seemed to really shine at the low end which made them very drivable around town - lots of grunt. Very reliable and simple to boot. Never had any transition issues once dialed in. Sounded awesome (I miss that). They throw a lot of gas into the head with not much throttle so if you want mileage be very gentle otherwise it's balls to the walls to about 5000 and then flattens off (depending on your cam). I think you want to upgrade the ignition to get a nice big fat spark as well. What's your alternative, triple weber$$$$? The 38's just bolt onto the same intake as the Zenith or 32/36 (if you already made that switch).

If I had any issues it was in the initial jetting which, because of altitude, meant a bunch of combinations to try but after I added an air/fuel meter and o2 sensor it was sorted. The bother was that changing mains and air corrector jets meant just about removing the whole top half of the carb body - total pain.

All in all no regrets and a great big pile of fun.

Doug

Doug
 
3.5 L with cam & 38/38 Webers

+1
BLUMAX is fitted and powered with the above including a cam designed by our BMW guru of years ago--and still with close BMW relations Hans Herman--the Danish Engineer, not the German race driver. BTW--it was strongly hinted that Hans is the engineering genius who taught Schrick the art of cam design. In recent years Han's expertise in cam design has served both BMW and Honda race teams well.

It did take time, patience and considerable fiddling to get the jetting setup balanced out--but the results are very good--lots of grunt--read torque--from around 1500 to 5000--then just reach for the next higher gear--no real need to spin beyond 5000.

Response is very satisfying but don't expect high miles per gallon as the temptation to hear and feel the combination of sound and action is too much fun to expect fuel economy too. Steady cruise with only gentle use of the go/sound pedal delivers about 18 mpg in 5th gear.
 
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