Questions from distributor rebuild on a 340

[Dakota]

I've been reading the comments from Chryco and Shane Kelley on the "340 Timing" thread in the engine section, which got me curious about the condition of the my distributor.   So I did what I usually do and took it apart, and now have a bunch of questions.

Background:  70 Challenger w/ a 340 4 speed. The distributor has the electronic pick up instead of points.  Mild cam (stock or close to it).   Originally had a carb, but switching to FiTech throttle body injection.

1.  The mechanical advance springs are 2 different sizes.  Is this is normal?

2.  There was varnish at several internal locations which was probably oil or grease at some point in the past.   What lubricants should be use on this and where?

3.  The distributor shaft has some score marks and some smooth areas in the spiral cut at the top (the part that would tie in to the rotor).  Is this a normal appearance or has there been excessive wear here?

4.  The mechanical advance weights are marked "1889264".   Would these be the right weights for a 340 running a manual transmission?

I will probably have more questions on this same subject, but these are all I can think of right now.

[73_Cuda_4_Me]

Based on the dizzy in my 73 340 Automatic (with 70 engine in it at the current time)...

1. Springs are two types, but one of yours is not correct... there should be a second heavier-gauge spring that has one end elongated so it doesn't affect timing until at higher rpm, and it flattens the advance curve by adding secondary spring tension above that RPM (around 3,000)...

2. Use a light grease on the shaft bushing, and the counter-weight pins, and a couple of drops of engine oil on the 'sponge' feeder that should have been in the center shaft hole above the cir-clip holding the advance plate to shaft...

3. As long as advance plate can pivot on the shaft, the spiral/smooth cut of the shaft should be okay... I'd use a honing stone or fine file to knock any score marks down, though... the rest is identical to mine.

4. I have the same counter-weights in mine, so probably no difference between auto and manual for the dizzy... carbs yes, dizzy no?

[gzig5]

Glad you brought this up.  I'm taking mine out this week for a clean up and installation of the FBO limiter plate. 

The springs were set from the factory, but I don't know off hand what they are, but want to say heavy on both.  You can get different weights and tune the advance curve of your distributor to your needs.  You can send it to someone with a distributor machine or do it yourself with a timing light and a tachometer.  Depending on your cam, fuel, and ignition configuration, you may benefit from a non-stock curve.  That is about as far as my knowledge goes and I need to start researching what springs I "need" for mine.  But from reading on this and other forums something that has initial between 15-20 degrees with the total 34-36 degrees and all in between 2500-2800 rpm seems to be a sweet spot for most combos of street driven 340s.   Using vacuum advance can change these numbers.  I'm currently not using it, but I need to better educate myself on the topic.

[73_Cuda_4_Me]

On the bottom of the advance plate there is a stamp of how much advance is built in to the mechanical advance unit, and different vehicles had different amounts of advance... mine had 15 degrees of dizzy advance (30 degrees crankshaft advance). Yours 'may' be different.

Since I'm running a higher duration cam, it likes about 15 to 18 degrees for initial timing, so the mechanical put in another 30, making it 45-48 total.

I made my own limiter plate, and set slots at just over half the length, for 8 degrees dizzy (16 degrees crank), for a total of 31-34 total when all in.

I shortened the slots on the inside edges, so that there was more tension on the springs at idle, that way mechanical starts advancing at around 1200 rpm instead of 900 (I was getting timing bounce of around 5 degrees at idle with stock spring setup and this cam).

[Dakota]

and a couple of drops of engine oil on the 'sponge' feeder that should have been in the center shaft hole above the cir-clip holding the advance plate to shaft...

Any idea where I can find some of that sponge feeder material?   There was nothing in that area of my distributor but some cooked oil.   My attempts at creative wording in Google didn't lead to anything close.

[73_Cuda_4_Me]

It reminds me of a piece of a brown scotch-brite pad... about a 1/4" thick...

I think the technical term is a 'wick oiler'... we had some on some old lathes at the shop I used to work at a long, long time ago... there was an oil cup with a wick at the bottom feed hole... used for bushing oilers... we actually replaced some with some thick felt pcs...

Edit: it also reminds me of the felt used to line winter boots with the removable foot inserts... the correct lubrication schedule is 1 or 2 drops of 10W oil each year...

[jimynick]

Go to the local hardware store and buy a cheap package of chair leg pads, you know, the ones you stick on the bottom of chair legs to prevent their scratching the floor and cut out, or if you have the tools, punch out the size you need and lube 'er up. 

[Chryco Psycho]

I agree that the spring s are not stock & being that light on the one you could have difficulty idling it consistantly.
IMO a limiter plate or welding the slots is a must so you have more initial timing without overadvancing at higher Rpm

[Dakota]

On the bottom of the advance plate there is a stamp of how much advance is built in to the mechanical advance unit, and different vehicles had different amounts of advance... mine had 15 degrees of dizzy advance (30 degrees crankshaft advance). Yours 'may' be different.

@73_Cuda_4_Me Is this the stamp you're referring to?  So "11" would mean 11 degrees of mechanical dizzy advance, 22 degrees of crankshaft advance?  I didn't see any number stamps elsewhere on the distributor, so I'd appreciate seeing an example of where to look if this isn't it.

[Dakota]

Another dizzy rebuild question:  What other paths exist to reach the dizzy springs (or change the position of the FBO lock out plate) on a stock distributor besides removing this "y" shaped spring clip? My hands are not small, so reaching this little bugger in disassembly and reassembly has not been fun.  It seems that there's no way to get the pin on the vacuum advance arm re-inserted unless the plate holding the reluctor magnet goes on last.     

[Chryco Psycho]

I have found it is possible to lift the advance plate just enough to remove the vacuum advance arm without removing the clip

[73_Cuda_4_Me]

The 11R stamped on the plate is correct as being the amount of mechanical advance for that distributor... 22 degrees crankshaft...

With that plate and depending on your cam, if it likes an initial advance of 15 degrees at idle, you won't need a limiter plate!

I have been able to do just as Chryco suggests... lift the plate just enough to get the vacuum advance arm pin out...