m30 / m90 curiosity question

rsporsche

rsporsche

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been wondering about this for a bit ... question is which engine models had single width timing chain, which ones had double width? can't recall anybody ever talking about it, but i know both exist.
m30 b28
m30 b30 <double 1974>
m30 b32
m30 b34 (US)
m30 b34 (euro)
m30 b35 <single 1989>
m90 <single 1979> <double 12/1980>
 
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My m90 has a single. From a 735i E23 Sept 1979
 

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My M90 has double chain. At least now and through out my ownership the chain has been double. Engine origin M535i Dec 1980.
View attachment 220729

Sami
 

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SamiA said:
My M90 has double chain. At least now and through out my ownership the chain has been double. Engine origin M535i Dec 1980.
View attachment 220729

Sami
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Curious if you have the VIN on the engine. RealOEM shows the 1980 535i as having a single row. For all the cars I looked at on RealOEM, the double row sprocket is listed in the figures, but it is greyed out, and only the single row is actually shown in the parts list
Screenshot 2026-06-09 at 8.05.37 AM.png
 
a note from the engine maestro - @sfdon says that the early engines had 2 row chains and quit at some point as it wasn't needed ... and from then on it was single row.
 
ScottAndrews said:
Curious if you have the VIN on the engine. RealOEM shows the 1980 535i as having a single row. For all the cars I looked at on RealOEM, the double row sprocket is listed in the figures, but it is greyed out, and only the single row is actually shown in the parts list
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I do have it: 4145730

1781025116508.png


Sami
 
SamiA said:
I do have it: 4145730

Sami
Click to expand...
Very interesting that was a December 1980 car. That one comes up the same as my 1980 M90 (5549667, March 1980) as a single row in RealOEM.

And reading @rsporsche 's post it may be an obsoleted thing. I'll have to go take a look at mine again. It's been a long time since I had the valve cover off!
 
as Don mentioned, 2 row chains are harder to find. now that i think about it, my 1973 Bavaria had a double row chain under the valve cover and my '79 e12 528i and '83 e28 533i had single row ... all 3 of my 2002 had 2 row chains
 
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The cut-off for duplex should be somewhere around end of '79 to the best of my knowledge, therefore, I see some unexpected findings here :)

You did not ask for it, but I can confirm S38B36 double chain :):

20260608_230912.jpg
 
So here is the information I always thought would be valid:
Double chain in
E3 2500 2800 3,0 S Si SA 3,3 L Li
E9 2,5 CS 2800 CS 3,0 CS CSi CSL
E12 525 528 528i 530 bis Bj. 11/1979
E23 7er 728 730 733i bis Bj. 11/1979
E24 630 633 CSi bis Bj.9/1978

Part number for the sprocket for duplex is 11 31 1 253 112; you will not find it used in the 3.5 engines
 
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