Distributor cap and rotor replacement

[Rushfan1]

Car is running great but I have a new distributor cap and rotor in hand (got them from Bav Auto) and thought it would be a good idea to change them as it's been 23 years and 50k miles since it has last been changed.

Thanks in advance for excusing this basic question...I just wanted to confirm that this is a simple change that won't mess anything up (i.e. the timing). After all looking at the Hayne's manual, I'm just replacing the rotor as opposed to the distibutor itself. In other words, is it just a question of labeling the wires, popping the spring clips off, removing the distributor cap and then popping the old rotor out and replacing it with the new one?

[epmedia]

You don't remove the distributor to replace the rotor. The rotor just pulls off, the rotor has an alignment tab so make sure you get that correct. Put a few drops of engine oil in the shaft under the rotor before you install the new rotor. Don't break the center carbon button inside the cap when you install it.

[Rushfan1]

You don't remove the distributor to replace the rotor. The rotor just pulls off, the rotor has an alignment tab so make sure you get that correct. Put a few drops of engine oil in the shaft under the rotor before you install the new rotor. Don't break the center carbon button inside the cap when you install it.

Thanks so much. I meant to write "remove the distibutor cap", my bad.

[epmedia]

Thanks so much. I meant to write "remove the distibutor cap", my bad.

I figured you 'meant' to say that
On a side note, I've never seen the inside of a cap that's been on for 23 years!

[Bimmerknut]

You WILL need to reset the timing any time you replace the cap and rotor and/or plugs or points if you have a pre-80's car.

[Rushfan1]

Please see attached photos, there is the existing rotor which is currently in the vehicle and then the new one I got from Bav Auto (part 04 038, it says on the box that it's good for a 320 i, 80 onward). Do I have the right rotor as there are obvious differences between the two. In addition, since it is a 1980 and older model, is it just a question of lifting the old rotor out, adding some oil to the shaft as mentioned above and placing the new rotor in the same position as it is now?

E21 Rotor 007.JPGE21 Rotor 008.JPG

[epmedia]

The old rotor is interesting. I wonder if it's the rev limit type I heard of.

Look inside the new rotor, you'll see the alignment tab which engages to the slot in the shaft.

[Tom D]

it's fine, just lift the old rotor straight up and press the new one on. there will be some resistance and it will rock back and forth when trying to remove the old one, this is normal.

- - - Updated - - -

You WILL need to reset the timing any time you replace the cap and rotor and/or plugs or points if you have a pre-80's car.

mariner, this statement is misleading and will keep guys from tuning their points for lack of a timing light.

timing is never required while changing plugs, rotor or cap.

timing is never required when changing points, but I would suggest that you at least check it afterwards. the reason being is that spark is generated by the spinning of the distributor shaft. that shaft is gear driven by the cam which is chain driven by the crank. because these are all connected mechanically there is no way the timing will ever change. with points there is a small exception. as the nylon heel of the points wears down (the reason you grease them) the points will open later and the spark timing is retarded. this timing change however is very small. if in the beginning the points are installed, the gap set to specs and the timing set then when the next set of points are installed and the gap set to spec the timing will be exactly where it was the first time it was timed. the only reason to check would be if the heel of the new ones are different in length then the first ones.

- - - Updated - - -

The old rotor is interesting. I wonder if it's the rev limit type I heard of..

that's exactly what it is, I've never seen one myself, but supposedly it removes the contact at 6400+- rpms.

[JBasham]

Anybody else have any experience with those rev limit rotors? I have been thinking of getting one.

[Jeroen]

The new rotor without the mechanical cut off or rev limiter is not the correct one for your car. Your car has no electronics to engage a rev limiter, that's why carb and K-Jet cars have this mechanical limiter incorporated in the rotor operated by centrifugal force. Even though I know European cars better I'm quite sure this is the case with US spec vehicles as well. So with the new rotor currently you don't have a rev limiter at all. On the early 320i (M10B20) you need BMW P/N 1211 1 360 605, on the later models (M10B18 from Sept 79-on) P/N 1211 1 272 144 which I believe is your old rotor.

[Tom D]

I don't agree. It's more a matter of choice then it is right or wrong

[Jeroen]

If you don't mind driving without a rev limiter, I'd rather have it as a fail safe.

[Tom D]

I've been driving for the past 41 years and never had a rev limiter until I bought my first car with electronic fuel injection, keeping it out of the red zone is part of the driving experience. besides, most people don't spend time at red line anyways.

- - - Updated - - -

If you don't mind driving without a rev limiter, I'd rather have it as a fail safe.

there's a flaw with your reasoning, most destructive over revs don't happen because you accelerate beyond a 6400 rpm limit, you would realize that you're spinning too fast before any damage occurres. most devastation comes from missed shifts, like grabbing 3rd instead of 5th, or 2nd instead of 4th. when this happens a rev limiting rotor is going to do nothing but add to the insult because you payed $50 for it instead of 10.

[Rushfan1]

So how the heck did I get that original rotor? A lifetime ago in 1989, my folks were in Europe and I asked them to leverage that trip to bring home some routine maintenance parts for me from a BMW dealer. Included in that batch of parts was the rotor. I'm quite sure the part number for that was 12 11 1 362 221.

[Jeroen]

P/N 12 11 1 362 221 is for the Euro series 1 M10 versions, probably because they had these on stock. Will work fine but it is possible the limiter cuts out at a lower rev count.