Distributor and rough idling - Bosch 046

[paul_GB]

Hi, my car suffers from rough idling and has done dispite an engine rebuild (!). From reading heaps of excellent threads in the forums I have high hopes the 046 dist setting might be the prob (or part of it)..... When I removed the dist from the car for the rebuild I noted a spring BELOW the drive dog (helicoil gear) that drives the dist shaft. Stupidly I am pretty sure I re-installed in the same way.. now I realise there should be a spring ABOVE that dog gear and between the dog and the dist shaft..! Hoping this is the source of the idling problem (please). Also I wasnt aware of the offset in the drive mating slot (dog to dist shaft) so I am suspicious this is wrong too (!). All together not one of my best jobs.!!!! Its an early car (1964) with the vacuum advance arrangement (vacuum tube on top of throttle housing). With the current orientation of the dist the vacuum cell is pointing forwards (towards the radiator) and I am suspicious this is wrong. On reading the threads it seems older type dist should be pointing the opposite way, is it 180 deg out...?? If these things sort my idling problem then my pagoda enjoyment will change massively for the better ;o)

I need to get a spring also from MBZ hopefully. Strange that the spring I have fitted wrongly sits very neatly UNDER the dog gear.. almost like it was meant to be... it had me convinced. Photos attached (hopefully) might be useful in understanding the words above.. ;o) Many thanks

[J. Huber]

Hey Paul. I can tell you that my distributor is turned 180 degrees from yours. Try turnin' her around. Good luck. Engine bay looks clean!

[paul_GB]

Thanks James. I am pretty convinced my dist is 180 out now. Ive ordered the spring from MBZ (£6.50).. should be here tomorrow ;o). Then will follow Joe's 'how to' instructions to turn the dist with minimal impact to other settings. I am hopeful..

[Benz Dr.]

The distributor IS pointing in the wrong direction but in reality, it doesn't matter all that much. As long as everything is in time the engine will still run OK. You can move it around 180 degrees to its normal orientation and simply index the plug wires accordingly.

You have a vacuum advance unit installed BTW.

[Naj ✝︎]

Hi, Paul,

As a matter of interest, have you retorqued the head and rechecked the valve clearances since starting the engine.

We had loads of running issues with a 220 SE rebuilt engine because all the valve clearances were too tight.

naj

[paul_GB]

Aha - Actually no, I havent rechecked the valve clearances since retorquing.. I need to do that then next also..! Thanks
Current task is to somehow pull the helicoil drive dog out up thro the distibutor housing 'tube'. Anybody done this..? A magnetic pick-up tool would be ideal for this. From memory there is a spring fitted UNDER the drive dog that shouldnt be there. I need to get this out. Can anyone confirm there should be no spring there. I will then instal a new spring above the dog.. under the dist.

[jacovdw]

Paul,

If I remember correctly, there should be a threaded hole in the top of the helical drive that mates with the male part of the distributor drive. Screw in a long M5 bolt and then it is just a matter of removing it with a twisting motion (anti-clockwise if I remember correctly).

You can then use the bolt to help you re-index the drive.

The only 2 springs that I remember are:

• the large one that covers the pin on the bottom of the distributor (the one that holds the cog on the shaft)
• the small one that fits between the mating surfaces of the male and female drive

Hope that helps.

[paul_GB]

Thanks. Great advice Jaco. Job completed, correct spring installed in correct location now (between dist shaft and helicoil drive), Timing, Dwell angle all set up fine and engine runs well and idle was nice and smooth too (at 800 rpm). In fact the best Ive ever had it. But after a few miles the rough idling is back so need to look elsewhere now.. valve settings is next (as per Naj's suggestion)..