kAs long as the ring didn't slip during your curve adjustments, the curve should be good. 

John - "The Hoosier Hurricane"

Thanks Hoosier, that's a good point.  My mechanical and vacuum adjustments should still be set correctly though, right?

1954 Crestline Victoria 312 4-bbl, 3-speed overdrive

Peeeot:

One more thing.  It is very possible that the damper ring on your front pulley has slipped, and the timing is not exactly where you think it is.  Try advancing the distributor then test drive it, advacnce some more, drive, etc. until you notice a ping, then back off until the ping disappears.  If that proves that the timing marks have moved, make a new reference mark on the pulley, not the damper ring.  The pulley won't move, but if the ring has moved once, it may move again.

John - "The Hoosier Hurricane"

So I finally got to make my adjustments.  When I was done, I had 2* mech. at 900 rpm, 4* at 1000, 12* at 1400, and 18* at 2000.  That was as high as my tach reads.  Vacuum was 8* at 6.5" HG, 20* at 12", and max of 24*.   These numbers are off the top of my head memory but I think they are very close to where I set the distributor.  Oh, and initial was 11*.

As for the test drive, there was marked improvement in pickup and power in general, though it wasn't quite night and day.  I didn't hear one bit of spark knock, even accelerating hard up a steep hill, so I guess I could stand to add a little more advance even.  All in all, I'm pretty pleased.  Without having a factory-fresh car to compare it to, I'd say its performance is on par with what I'd expect of this engine/transmission/axle/vehicle combination.

1954 Crestline Victoria 312 4-bbl, 3-speed overdrive

So far as I know - there is only a spring preload adjustment available on the later vacuum pot (that uses the hex key adjustment). Same as the shimmed version. I have heard that there are different part numbers of cans - that have more or less total travel.

If you've got the engine at idle, and tuned for max vacuum - say 17 inches Hg - then you check initial timing with no vacuum advance. This is then compared with what you get when the full vacuum is applied to the vacuum canister - the difference relates the existing spring preload to the advance travel. Adjusting the spring preload upward reduces the travel - and vice versa - which you knew. But I don't think there is an adjustable "stop" as such in the later canister - except maybe absolute maximum.   

The shimmed version could definitely have an advantage - if you replace the fiber tube with a longer one that limits travel (and you are looking for less).

 
 Steve Metzger       Tucson, Arizona

uh oh, I hope this isn't a duplicate post!  I know it is preferable to avoid those :-/

I have been patiently awaiting an opportunity to put everyone's advice to practice on my car, but the weekend was busy.  This afternoon, though, I'm going to get my distributor adjusted, and I'm looking forward to posting the results!

About the different vacuum modulators--the hex key type should work with my distributor, but a new one is more than 50% of the cost of a replacement distributor, so I'm going to stick with my less simply adjusted unit.  Once the adjustment is made, I don't plan to fiddle with it any more.  As I understand, the non-hex units also have the advantage of being able to adjust total advance in addition to spring rate.

1954 Crestline Victoria 312 4-bbl, 3-speed overdrive

Hello Steve,I was making that suggestion for the fellow who started this post.I thought it was unfortunate that he ended up with that advance unit on a "new" distributor.Its obviously much easier to adjust the one that uses the Allen key which is what I got on the one I purchased.I am following this post with interest because he is getting better response than I did asking this question a couple of weeks ago!

  

Hello:

  You asked where to begin on distributor advance curve. I would suggest start by dropping in the new distributor, setting the initial timing to about 10 % BTDC with the vacuum advance pulled and plugged. Then hook up a manifold vacuum gage and at idle out of gear advance the distributor for highest vacuum reading. Back off the advance about 2 inches of vacuum and take it for a spin. Unless you are using a 5 speed and 4.11 rear gears thats really all you need to do. The rest is just to sell Hot Rod magazines to guys. Pete

Mark -That recent "Mustang Monthly" article I mentioned in another thread probably could help determine this vacuum pot interchange issue. The early dizzy is an "Autolite" and the later is a "Motorcraft". Apparently the '64 and '65 Mustangs have a similar change-over situation at that date.

I don't have a copy here at the office or I would try to scan it for you.....might be Monday before I could get that done. Send me a PM with an email address if you want a copy and I'll send it to you as an Adobe "PDF" file.

 
 Steve Metzger       Tucson, Arizona

I realize the distributor is "new" but you could still swap the advance unit for one that adjusts with the allen key I think.Seems to me its much easier to adjust instead of keep playing with shims and spacers.Would the 2 different style advance be interchangeable?