I hope this isn't a stupid question, but I gotta ask and I can't seem to really find the answer.

I set my timing to about 13BTDC at ~900 RPM with vacuum advance removed. I would have lowered the RPMs to about 700, but it seemed to be running rough, so I left it at 900. When I rev it up to 3000RPMs (still without the vacuum advanc) and check the timing with a timing light the mark seems to be in pretty much the same position.

It should be advanced somewhere in the range of 11 degrees, correct? Does that sound right? Does this mean that the mechanical advance isn't working properly?

I have a D611-54 dizzy with an MSD6 series ignition and an MSD coil. I am running an E31 head on an L28 block with an ISKY stage III cam.

Thanks for any help.

Hook up the vacuum advance, thats what it does.

I don't recognize the part number you're giving, so I'll assume that the dizzy came out of a Z. If it did, then by 3k rpm you should be seeing ~20 degrees of additional advance, more or less depending on which dizzy it is. So I'd say you are correct, your mechanical advance isn't working. With the engine off, take the dizzy cap off and see if you can move (rotate) the plate. You should be able to move it a bit. If not, then that's a clue

Thanks, Daniel. I'll try that this evening. I'm definitely not seeing 20 degrees of advance.