Pinto Car Club of America

Pinto Guys,
   Some of you this may not apply to but most of you I am sure it does apply to. When we decide that our car needs a tune-up we get out the timing light and the book and proceed to set the timing at the prescribed point. But if your centrifical flyweights are not returning  back all the way then everything you are doing from setting the timing to the final adjustments on the carb are inaccurite.
There are two forms of ignition advance on a distibutor. #1 is the flyweights and #2 is the vacuum advance...Please note that flyweights is #1 because if these puppys don't return all the way then you do not achieve an optimum tune.
It is easy to see if they are not returning...simply remove the distributor cap and turn the rotor to it's advanced position till it stops, then gently release it, take your finger and see if it will move any farther back to the retracted position...if it does then the springs need to be tightened up till it will not move further when released. This miniscule amount of movement can account for 1-2-3 and even up to 4 degrees of advance in the timing that you may not realize that you are getting. 
The function of these flyweights is to advance the overall constant timing as the secondaries kick in(they do not gradually do anything, they are in or out) and that point is generally between 1200 and 1700 rpm.
I have found that old cars( like the Pintos we are rejuvinating)have worn springs sometimes even broken...I have seen new distributors that have new springs that are not sized right. A running tell tale sign that these springs are to loose is after a tune-up it is hard to get it to idle. If the idle is low one would turn it up but then the loose springs allow for advance to soon and the engine begins to idle to fast so one idles it down and the engine stalls. There may be allot of guys out there with their idle to high for just this reason. Another tell tale sign of this problem is when you have the timing light on the engine and the timing mark is bouncing around making it hard to zero in on the timing mark. That timing mark should be absolutely still.
So what do you do???
Remove the vacuum advance/points plate and look them over. The spark cam has to come off to get the plate off but then put the spark cam back on and do the same turn check as above(now you can see what is going on)for the slop. This is a good time to put a little lube on the flyweight posts and the little nylon buttons that the weights travel on.
What I do with the springs is to cut off the spring hook and fold the next coil down and make a hook with it. Essentially shortening the spring a bit. Do this just one coil at a time till there is no slop in the retracted position.
I bring this up because this is a very often overlooked componant that IS a DIRECT factor in how an engine is tuned for optimum performance. I hope I explained this in an understandable manner and I would be happy to answer any questions.

                                                          High_Horse

and with the shorter spring are you not also limiting the rate at which the sprinf=gs stretch as well?  this will limit the rate at which the timing advances and will also affect driveability

Srt,
    Very good question. The answer is no because you are just reducing the space that is preventing the flyweight from returning the spark cam to it's full retracted position which should not be there in the first place and this is just a small space and although not critical it can hamper a good tune-up. One might not need to cut off the hook(s), just making them shorter might do the trick. Keep it in mind here that the primary goal is to set the timing correctly at idle.
Here is a note...I have seen some distributors with one light gauge spring and one heavy gauge spring. I could never understand why they would have put such a heavy spring in there in the first place. If you have a heavy spring replace it with a match to the lighter spring and chuck that heavy spring just as far as you can.
Here is a question for the cam guys who have to idle a little higher...Are your flyweights extending before your rpm is at that cam range?
One can see when the advance is taking place with the timing light. Plug the vac. advance like normal, hook up a tach. under the hood, and see where the advance jumps as you increase the idle.
                                                   High_Horse

I came across a picture of the distributor with the vac. advance plate removed so one could see what it looks like.
Yes, there is an advance curve and that is what it looks like but picture the curve with a big spike at the front of it. All one is doing is removing the spike. It just so happens that where the spike is is where one is trying to set the timing. This is something that the regular guy can do.

                                                     High_Horse

thank you !

OK... I read it again High_Horse, guess I do understand a bit of what you are saying here.

I've had more than 1 pinto that I have had to set the idle to high to keep it running including the current one I've been asking questions about. Also tried to time this pinto w/a light and had the bounce effect you refer too. Now I know what causes it... bad distributor. learned something new today  ;D