Ignition timing

[Kevin1]

Fiat specifies 10Ëš before TDC for the ignition timing on our 1980 Spider 200 FI. After doing some experimenting with it the engine seems to run best with the ignition timing set at 20Ëš before TDC. It seems to be a bit extreme, but it runs well and I haven't heard any pinging, either when intentionally lugging the engine (5th gear, 35 mph, full throttle) to test it, or at higher revs (5-6000 rpm).
Even though I can't hear any pinging, is 20Ëš too much, or am I pushing my luck?

[jfrawley]

I just went through something similar to what you're experiencing. Check out this thread:

http://www.fiatspider.com/f08/viewtopic.php?f=5&t=5470

Not saying that's your problem, but the symtoms seem the same.

[Kevin1]

That does sound similar. This weekend I will check the vacuum advance and the cenrtifugal advance to see if they are working. After I find out what is happening I will post back.
Thanks for pointing out that earlier thread!

[Kevin1]

Ok, after having time to look into this again, here's what I found.

1. Checked the mounting screws for the pickup module to see if they were binding the base plate, and they appear to have plenty of room.

2. Vacuum advance: vacuum present at the diaphragm, but no movement. I double checked it with a vacuum pump and still - nothing. Will need to replace the vacuum advance mechanism. The base plate does move if I pull the vacuum advance lever by hand, and returns freely when I release it. Since the vacuum advance is DOA I plugged the hose to close off the vacuum leak for now.

3. Centrifugal advance: This appears to be working, but in a limited fashion. I left the static timing at 20 degrees advanced, where it has been. Maximum advance comes in at about 3,750 rpm. Measuring with a digital timing light that can read the amount of advance gives a total advance of 35 degrees at 3,750, or only 15 degrees of centrifugal advance.

It seems clear that this distributor needs some help. First, I will replace the vacuum advance module. Second, I need to find out why there is so little centrifugal advance. According to the factory manual the centrifugal advance should be 28 degrees, +/- 2 degrees. With the distributor open there is one light spring and one heavy spring on the arms, and the seem to move freely by hand.

Once everything is working I should be seeing 10 degrees static timing plus 28 degrees centrifugal advance to give 38 degrees total advance. Is that correct?

Any suggestions what to look for next?

[Kevin1]

Centrifugal advance problem solved! The plate that the two advance arms are mounted on had a groove worn into it, stopping one of the arms from fully advancing. So, a little filling weld and a little filing to smooth things off and there's 22 degrees of advance by roughly 4000 rpm, measured at the crank.
A new vacuum advance assembly is in the mail. When it is installed, do I set the timing with the vacuum advance hose disconnected and plugged?

[So Cal Mark]

yes, set the timing without the vac adv working

[racydave]

You could try and find one weaker spring, just for curosity! That could make it a little hotter on the low end...

[Kevin1]

You could try and find one weaker spring, just for curosity! That could make it a little hotter on the low end...

Well Dave, are you psychic or something? It turns out that I will use different springs after all.

Lesson learned: After taking your distributor apart in the house (lighting is better) do not drop everything in the dark on your way back out to the barn! Otherwise, you will be shopping for springs and washers. Like I was today. Amazing how fast those springs can disappear into the gravel.

Napa had springs in a GM HEI advance recurve kit that fit our distributors. The kit comes with three pairs of springs in three different weights. I used one strong and one medium spring as they seemed closest to what was in there before. The lightest springs in the set were much lighter than the springs that I lost. When I have time I'll check the advance to see what combination of springs work best. Centrifugal advance is working again, the new vacuum advance module works, and the car runs well timed at 10 degrees advance.

[racydave]

Are you psychic? When I ran a dizzy, I swapped some GM springs that I bought in a kit too! I also made custom weights from that kit. You are having French toast and Bacon tomorrow for Breakfast...