Crankshaft pulley diameter?

[VWScott]

I've read so many posts on timing with much conflicting information. So I am at the stage where I want to check what my current timing is but I'm not sure what it should be. Mine is '76 with smog removed from set up. I have the original distributor in place with the vacuum can that has both advance and retard.I have vacuum cap on retard.Advance is plumbed to vacuuum port on Weber 32/36 I checked the valves yesterday and all was good.I marked pulley at TDC and at 180 degree point. Checking the sight area in the bell housing was a bit pointless.I can barely see anything. So what I want to do is get a measurement of pulley diameter and mark off my desired spec for advance.

[visionaut]

There are different crank pulleys with various diameters and # of pulley wheels…

 

FWIW, my 76er has engraved timing marks (OT & Z) in the solid space between the innermost (my AC)  and outer (my alt) pulleys.

['76mintgrün'02]

You'll probably need to measure yours and then create a scale to fit.  Or make lines, or whatever.  The flywheel is more accurate.

 

You need to clean off the flywheel and add paint to the OT line (TDC) and BB (25*) to make it easy to see.  It's worth the little bit of effort.

A variable timing light is an essential tuning too, in my opinion.  Do you have one?

 

I've got a '76 with a #164 distributor and am using manifold vacuum now, having used the Weber port(ed) in the past.  It is running better than ever.  I also backed off the total advance when I made the switch (switched distributors at that time too).  I have 35 all in, with 4* at idle, plus the vacuum pod (which is currently adding more than I'd like).

 

John76 has that dual-action pod on his '76 and is using manifold vacuum too.  (trend-setter)

 

I'd recommend setting total advance to 34 and see what that leaves at idle.  I'm guessing it won't be much; but the manifold vacuum connected to the front of your pod will pull in around twelve more at idle.  It'll cut out when you mash the pedal. 

 

We have been discussing this topic in another thread.  You're welcome to join us!

 

https://www.bmw2002faq.com/forums/topic/335822-weber-3236-vacuum-advance-question/#comments

 

Sorry I can't answer your pulley marking question.  I do have unsolicited suggestions to offer though!

TOm

[Mark92131]

The "OT" line on the flywheel is hard to see, but if you stick a pencil with an eraser on the end down the viewing port with the engine running you can clean off the 25 degree BB, it makes finding the "OT" line easier.  Once you line up the "OT" line on the flat side of the viewing port, you can verify TDC on the front crank pulley.  For ignition timing, just cap the advance source, adjust the idle on your carb to 1400 RPM, and turn your distributor until the BB appears in the viewing port at 1400 RPM, lock the distributor down and reset your idle to 900ish.  If your distributor is working correctly, you should be around 12 degrees BTDC at idle and 38-42 degrees all in (2700 RPM+).  Reconnect the advance port on the distributor, cap the retard and you should be good to go.

 

Mark92131

['76mintgrün'02]

2 minutes ago, Mark92131 said:

If your distributor is working correctly, you should be around 12 degrees BTDC at idle and 38-42 degrees all in (2700 RPM+).  Reconnect the advance port on the distributor, cap the retard and you should be good to go.

 

If the advance port is connected to manifold vacuum 12 degrees will be added to those 12 degrees, for a total of 24 at idle.

Ported vacuum will not add advance at idle.

 

 

I had mine set to 12 at idle and 38 total, using ported.

Now, I have mine set to 4 at idle 35 total, using manifold.  (different distributor/slightly modified)

 

I was getting pinging between 2-3K rpm with the previous settings.

Now, I don't have that problem.

 

I haven't looked at the BB lately.  Based on the curve, it should be at around 1900 rpm, (adding 4 degrees for static timing).  The graph is drawn to show distributor advance, which doubles at the crank, along with rpm.  The BB is at 12.5 degrees (25 crank) and all-in happens at 1600 rpm (3200 crank).

Tom

[jimk]

I never liked marking the line.  I marked with one color ahead of the line and a second color after the line.  With only the line marked,  if the line is not in the window, you have to go fishing to find the line.

[TobyB]

Wrap a string around the perimeter, measure it, divide by 360, and then mark your string accordingly.

 

I then wrap the string back around the pulley, and hit it 

with a chisel at the important points, and with a punch

at the intermediate ones that I might be interested in later.

Then use some silver Sharpie to make the lines and dots pop.

 

Takes about 10 minutes, and making a  pointer takes maybe half an hour,

and then I just don't have to think about it any more.

 

t