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Old 11-24-2004, 10:23 PM
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Bosch Distributor Drive Orientation Question

In the name of 'preventative maintenance and in dire need of something to do, I recently pulled the distributor from my 280s and rebuilt it. Problem is, I neglected to mark the orientation of the bottom drive in relation to the distributor shaft. Here's a pic of what I'm referring to.

Noting that one hemisphere of the drive is slightly larger than the other, if the larger is facing towards me currently, the rotor is in approx. the 2 o'clock position. Is this correct or am I 180 degrees off? Which leads to my second question.

When I pulled my dist, I didn't bring the motor up to TDC, just yanked it, thinking it would go in as it went out. Will I need to turn the motor to #1 TDC to get the dist back into place and functioning?

Thanks and Happy Holidays.

Last edited by JMela; 11-25-2004 at 01:21 AM.
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Old 11-25-2004, 04:02 AM
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gimme a low-tech 240D
Join Date: Jan 2003
Location: central ky
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One thing you can do is drop the distr in and *then* set the engine at #1 TDC with crank and camshaft lining up to their marks. The distr rotor should be pointing at either #1 or #4 post. Otherwise turning over the engine w/out distributor would make me fear the oil pump gear could get dislodged somehow.

Or if you've got the balls, just take a chance at installing the distr and see what happens when you try to start the engine.

What's involved with distributor rebuild? New spindle/cam and centrifugal advance springs, plus thorough clean and lube?
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Old 11-25-2004, 09:11 AM
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I assume you know where the rotor was when you took the dist out..
so, if the dist drops right in when you have the rotor where it was , it is correct. if it does not and the rotor has to be turned 180 degrees from where it was , the drive is 180 out . so, remove pin and turn it..[ the drive will not go in freely if it is not correct on the shaft, as the offset wont match with the drive dogs]
There is no need to turn engine to TDC to get it back in..
just be sure you did not turn engine after removal of dist...

or.. as DD says , try it .. if its out 180, it won't start ,,you gotta 50/50 chance..
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Old 11-25-2004, 10:10 AM
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Location: Brooklyn, NY/ Minneapolis, MN
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Thanks guys.

240DD - got a universal Bosch rebuild kit from Dan Caron (benzbarn(at) for $40 or $50, which consisted of new washers/bushings, new springs, new brass bushings for the driveshaft, new c-clips for the weights, , distributor clips, maybe 70 pieces, of which 15 or so were utilized in my rebuild. I'm running one of those Pertronix jobs so I didn't mess with the points nor vacuum mechanisms.

Disassembled everything, cleaned everything up, lubed and reassembled. Things didn't look too bad and I didn't have to replace the shaft bushings, which would require a shop visit in my case. Used this guy's site as for reference An enjoyable job and not too difficult. **Just make sure you mark where the drive sits on the shaft!
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Old 11-25-2004, 11:45 AM
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Should Be Right

If you didn't rotate the engine it can be 180 off. But drop it in and see where the rotor points..I would rotate to TDC and see where the rotor is pointing. You can pull the number one spark plug and see if piston is up and the rotor pointing to number 1....Jim
James A. Harris
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Old 11-25-2004, 12:08 PM
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Location: Long Island, NY
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just for reference, your motor's timing can be statically set by hand rotating it until:
- #1 piston is at the top of its travel, a very long screw driver resting on the piston crown is an easy way to gauge this.
- The mark on the cam tower lines up with the mark on the cam (it's thrust washer actually). Also, the two cam lobes for the #1 cylinder point away from the rockers. (If you're 180 degrees off on the cam, the lobes will be up against the rockers). On a benz v8, we're talking about the cam bank on the motor's right (your left looking into the engine compartment).
- The pointer on the block points to the 0|0 mark on the harmonic balancer.
- Mount the distributor so that the rotor points to the mark on the distributor body. The timing is more or less accurate if the points fire at this position next time you rotate the motor through TWO revolutions.

Note that these rules are good if you disconnect any one item from the motor. They're also good if you take the whole thing apart and try to reassemble it.

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