Does your total timing stop at 2000 when you have it set on 21L or will it continue to climb?

If it's not a street car you could lock the timing at 38*. You'd need a seperate ignition switch though. So you could crank it, then through the ignition switch on while it's spinning. It would be to hard on the starter for a daily driver. IMHO, FWIW

That's cool we finally got a trailer for the '66 and another "commuter car" for Melissa. So maybe I can get a little more radical with the 'stang.

A timing retard box or the seperate ign. switch, and I'd be tempted to lock ours in at total! Don't know what everyone else thinks about this. Maybe they'll let us know.

This has little to do with how quick the timing comes in,in fact if you use the 21L slot,you will have the worse case scenario for what you are trying to do. You will have to set the initial timing several degrees retarded in order to make sure that you do not have too much total timing. Most likely you will not even get it started,and if you do it will be hard. It will crank and crank very easily,but not fire the mixture soon enough to build the cylinder pressure to get it started.

On the flip side of the coin,if you use the 10L slot,you will end up having to have 16 to 18 degrees of initial timing in order to have enough total timing at the maximum that the distributor will produce. Most likely the engine will start,but it will really tax you battery and starter,because you are building a LOT of cylinder pressure at the cranking speed. Most likely it will turn over too hard to get it started once the engine gets hot.

The compromise solution is to use the 15L or 16L slot. Then you will only need 6 to 8 degrees of initial,which should be enough to get it started fairly easily,and still give you some room to experiment (maybe your engine will like 39 or 40 degrees total).

Now to get it in quickly. I am going to voice one concern before I explain this,and that is I am not sure what quality of gas you are running,so you should proceed with caution as far as getting your timing in early. I have ALL of mine in at about 1500 RPM ( a little above my idle RPM ),BUT I am running Turbo Blue which has around 108 Octane ,if I remember right, using the R+M/2 method. You need to sneak up on this if you are using pump gas so that you don't go into full fledged detonation at a certain RPM.

One way to do this is to take the stiffer of the two springs off completely,and then bend back the tab on the softer spring until you have the advance curve that you desire. This might result in too aggressive of an advance curve though on the street. You can also leave both springs on and bend the tab in on the stiffer one until it is quite loose,and then bend the tab in on the loose spring until you have the timing in a little too soon,and adjust the stiffer spring until you get the curve that seems to work best.

This is going to be a long trial and error process,but the work will be worth it. Your engine will be cooler in traffic,have much better throttle response,and get better gas mileage,if you get it right.

The information that I gave you doesn't even take into consideration the vacuum advance,which I assume you are not running. That opens up a hole other can of worms in and of itself.

Let me know if you have any more questions on this subject.

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'85 Capri
Cleveland powered
carburetted

'72 Pinto
CARBURETTED,draw thru turbo 4 cylinder. Runs good.

I figured I'd throw two cents worth in here. I set up a duraspark like that recently. The settings you mentioned (10 and 15 on old distributor and 16 and 21 on the duraspark) are actually double that amount at the crank. So basically whichever one you chose will give you double that amount at the crank. So here's the part that blew my mind. If you set it on 21 (like I did at first) it gives you 42 degrees of advance. You heard right 42 degrees of advance. So when I set my initial at 12 my total went up to 54 degrees. Believe me I checked, double checked, triple checked. After some investigation I figured out my problem.

As it turned out even setting the advance in the 16 slot still gave me 32 degrees of advance which is still too much. I wanted 12 initial and 38 total so I needed 26 degrees of advance. I had to use JB weld to close up the gap. I used calipers to set the width of the gap. It worked perfectly, but I'm not necessarily recommending this method. I also installed the light advance spings made by Mr. Gasket which were about $4.