HEI Distributor mechanical advance curve options

[Cadman-iac]

 Not sure if it has any bearing on the total advance or not, but can a weaker set of springs allow the centrifugal advance to continue to advance beyond what you would normally see, or do they only allow the centrifugal advance to reach maximum advance quicker than a stiffer/stronger set will allow?
 
 Im not sure if im incorrect in my thinking here about smaller /weaker springs, after reading so many different points of view over time, i just want to get this straight in my head.

 Rick

[Cadman-iac]

And as promised,  here's a picture of what I've been doing to build a distributor advance machine,  at least as far as the distributor end of it goes.

 I used a protractor that I got from Harbor Freight because of its size, it should make it easier to see once everything is working.


 The base, or mounting for the unit is an old adapter tool that would turn a hand drill into a drill press,  it's an old Dayton that I've had for over 25 years, and I've almost thrown it out about a dozen times, but each time I think, Murphys Law will catch up with me if I do.

 If you think it looks a little odd, you're right, I turned the adjustable head upside down so that the drill points upwards, and the distributor will sit above it once I've figured out exactly how to mount it.

 Then I'll make a control board to mount the coil, any switches necessary, and the wiring needed to make it work.

 Once I figured out exactly how I would mount the protractor to the distributor, it was a matter of cutting and drilling everything for clearance.  I also needed to add a reinforcement to the protractor itself to steady it as once I started to spin the shaft the whole thing began to vibrate.  So a small piece of aluminum plate was all that was needed to stop the vibrations.

 I started by first removing everything from an old distributor housing so that I could determine exactly where the mounting screws are located for each part, as I wasn't sure which ones I would have to use initially.

 More to follow as things proceed. Just wanted to show my progress so far.

[DJD OLDS 4MC]

Hi

Weaker springs will allow the advance to begin at a lower rpm, but will not increase the total advance available for centerplates and flyweights I tested. The combinations were taken to 2000 distributor rpms (4000 crank rpms) to make sure all the advance available was extracted.

[Cadman-iac]

Hi

Weaker springs will allow the advance to begin at a lower rpm, but will not increase the total advance available for centerplates and flyweights I tested. The combinations were taken to 2000 distributor rpms (4000 crank rpms) to make sure all the advance available was extracted.

 That's what I thought, but I had also read that a weaker spring could let your weights continue to advance, at least if your center plate is upside down from the factory setting.
 In the correct position, I wasn't sure if this was also the case.
 Thanks for posting.

 Rick

[Cadman-iac]

 Ok!!!! Well my preliminary tests show that I've got everything wired correctly, and the timing light goes off like it's supposed to, so it looks like the only thing left is to figure out exactly how to mount the distributor to this drill press tool.

 I did notice that an aftermarket ignition module, although it is good and the vehicle ran on it, in this test situation it does not put out as big of a spark as a factory ignition module does.

 That was also something that I had read earlier, so thought I'd swap to a factory module and see if there was any truth to that. Yes, it's true.

 
 Now, something I'd like some help with, as it's set up, the spark plug fires 8 times per revolution of the distributor shaft. Which is ok, except it makes trying to pinpoint the degree of rotation on the distributor for a particular plug rather difficult. 

 Can anyone tell me how to break this down a bit? Right now it's like trying to check your timing with your timing light connected to the coil instead of the number one plug.
 Is there any way to isolate a particular spark?

 I thought about taking an old pick up coil and an old timer core and cutting/grinding off all but one point, but I'm not sure if that'll work, or if I'd just be ruining a coil and core.
 Any thoughts anyone?

 Rick

[Cadman-iac]

 Well, I have a problem that is stumping me, I need some advice.

 Here's the situation.  I have my test distributor set up just like the one in the picture on page 1 of this thread, and it works very well, my timing light is going off at a minimum rpm of 400, which I think is fine, that allows me to pinpoint the degree at which it fires.
 
 Here's the problem, as I speed up the drill and it reaches 2500 rpm distributor speed, the light shows that the weights are deploying to maximum at around 1000 rpm, ( I have light springs on it just for initial testing).
 However, the tip of my timing indicator that is substituting for the rotor shows that im only getting around 4 degrees of advance. And I was getting a strange second flash from the timing light, you could see it on the distributor shaft and weights, like a double image.

 At first I thought I used the wrong pole piece, it was a 6 cylinder one with 5 of the points ground off, but it had some really odd shaped sections to it, so I switched to a standard 6 cylinder pole piece that looks identical to the 8 cylinder one, just 2 less points, then removed 5 of them. Works exactly the same, lights up the timing light at 400 rpm all the way up to 2500 rpm. This eliminated the second flash and double image, but I'm still not showing any more than 4 degrees of advance, even though you can clearly see the weights are extending completely.
 The center plate is a #482, and the weights are a #105, with just the lightest springs I have.

 I also thought that it might be the aluminum reinforcement plate I installed to keep the protractor steady, causing some weird interference with the pole piece somehow,  so I removed it and checked again, same result.

 I swapped the capacitor in the distributor as well, just in case, same as before.

 I took an old plastic rotor and ground it off on the bottom to clear everything, marked where the firing point is, and it still only shows 4 degrees of advance.

 Anyone have any ideas as to what would cause this? I'm at a loss now. I'll post pictures on the next post for reference.

 Rick

[Cadman-iac]

 #1 is the 1st pole piece with the odd shapes.

#2 is the standard 6 cylinder pole piece with 5 removed points.

#3 is my pointer for the protractor.

[Kenth]

The needle moves according to the speed of the centrifugal control turning, then you see the number of degrees on the scale per speed you are using.

[Cadman-iac]

The needle moves according to the speed of the centrifugal control turning, then you see the number of degrees on the scale per speed you are using.

 Yes, I'm aware of how it works, and it does to a certain extent, but it's not giving the results that it should be yielding.
 I can manually move the weights and watch the indicator move across the protractor the expected amount of degrees, which in this case is right at 20 degrees, yet when spun by mechanical means the indicator only shows an advance of about 4 degrees. It's this discrepancy that I'm trying to figure out. What is causing this?

 Yes, I can do this by installing on the engine and seeing what the results are,  but that's very time consuming, not to mention how difficult it is for me to reach the distributor.
 This bench test was to save my back and the gas needed to test each combination of parts. The gas used I can live with, but I'll be 68 in a month and climbing into the engine bay is not what I want to be doing at this stage of my life if I can help it.
 There's got to be something that I'm overlooking, but I can't think of what it might be, any help is greatly appreciated.

 Thanks,  Rick