Need Dual Point Assistance

[oldbee]

Just for giggles, check continuity on your pri.lead & grd. strap when putting vacuum to the can. Yrs ago stopped for gas & wouldn’t start back up, the strand wire was almost broken apart inside the crimped wire end. Ya never know.

 

[67 GTX]

THat may be normal with that much vacuum. Do this: Attach vacuum gauge to ported vacuum hose (cannister disconnected). Rev to 2500 and read vacuum. You can also read at manifold and compare the 2. How much vacuum at 2500 RPM? On the vacuum cannister arm that attaches to the breaker plate, there should be a number. multiply by 2 and that is the additional maximum advance the vacuum cannister adds to the motor at high vacuum. Cruising at 2500 low load you would have your 25deg from initial and mechanical per your measurement, and higher vacuum because throttle blades are partially closed and then you get additional vacuum advance pushing you out to about 45 degree if the can has a 10 on it. 2x10 plus your 25.

You also can read advance at idle vacuum disconnected. Should be your 12.5, Then using a vacuum pump at idle raise it to 15" and measure timing. If you see 32.5 subtract your 12.5 and that is the timing the vacuum is adding. Again 20 degree.

I believe I did that I got 23 in hg (not sure if it was exactly at 2500 rpm, but 23 was the highest it went).

I can't recall the exact number on the one I put it, but it appeared to be identical (was NOS) to the original one that I removed, and that had a 10 stamped on the arm.
So that means it will give me an additional 20 at my highest vacuum. But the motor starts dying halfway to the max vacuum, so it doesn't want total timing higher than the mid 30s? But I've even tried setting initial at 0 to give that buffer, and it still doesn't like the vacuum advance.

Problem is the motor starts knocking out at 13" or so, and the timing just goes haywire so I can't get an accurate reading.
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Just for giggles, check continuity on your pri.lead & grd. strap when putting vacuum to the can. Yrs ago stopped for gas & wouldn’t start back up, the strand wire was almost broken apart inside the crimped wire end. Ya never know.

Yep, tried that the other day. Compared resistance before and after putting vacuum to the canister, and the numbers remained the same. Also did that to check the resistance on the upper plate in the distributor itself, and same results before and after applying vacuum.

 

[HALIFAXHOPS]

Where in NY are you I am just N of Harrisburg PA if you want bring it here and we can throw it on a Sun Distributor tester.

 

[67 GTX]

Where in NY are you I am just N of Harrisburg PA if you want bring it here and we can throw it on a Sun Distributor tester.

Brooklyn, so it would be a bit of a trip. Thanks for the offer though!

 

[miller]

But the motor starts dying halfway to the max vacuum, so it doesn't want total timing higher than the mid 30s?

Minus the vacuum advance, mechanical, yes, should want total timing 34-36 degrees. That's where knowing how much mechanical advance you have, or if it needs to be adjusted.

I'm building up my Mallory dual point right now, pretty much in line with KK's. YL advance, same spring combo...looking at 18* initial, 18* advance...add those up, get 36*. Should be able to figure your's, knowing how much advance, wanted total, subtract for the initial.

 

[Dragon Slayer]

Does it knock on the road test too? Did you verify your firing order and #1 cylinder position on the distributor cap. Seems like you have reasonable performance on the distributor advances. Really the only way to find out for sure is a Machine test as recommended. Starting to think it is something else.

 

[HALIFAXHOPS]

Stupid question when you changed out the vacuum advance did you check the shim pack (washers) under the vac nipple to see if it was the same? If there are no shims and or spring in it as soon as it gets vac it can go full advanced instead of gradually. Just a thought.

 

[miller]

Problem is the motor starts knocking out at 13" or so, and the timing just goes haywire so I can't get an accurate reading.

I'll toss in another wild thought. Seeing those pictures, forgot how crammed the parts and pieces are in there.
Vacuum advance plate. Understand it rotates plate the points are mounted to. Don't remember just how it rotates. Question is, when vacuum does rotate it, from movement, wonder if the circuit could be getting grounded out? That would turn things to crap.

 

[67 GTX]

Does it knock on the road test too? Did you verify your firing order and #1 cylinder position on the distributor cap. Seems like you have reasonable performance on the distributor advances. Really the only way to find out for sure is a Machine test as recommended. Starting to think it is something else.

I haven't tried driving it with the vacuum connected. I figured it if wouldn't work in neutral, it wouldn't while driving. I have noticed that I do get some ticking from the motor now. While in gear, there is ticking. But when I put it in neutral and rev, no ticking.

So 12.5 mechanical advance is enough?

Stupid question when you changed out the vacuum advance did you check the shim pack (washers) under the vac nipple to see if it was the same? If there are no shims and or spring in it as soon as it gets vac it can go full advanced instead of gradually. Just a thought.

The new one didn't come with any, so i re-used my old spring and washer. The spring felt tense (had to put pressure on it on order to get the threads on the nipple to catch).

I'll toss in another wild thought. Seeing those pictures, forgot how crammed the parts and pieces are in there.
Vacuum advance plate. Understand it rotates plate the points are mounted to. Don't remember just how it rotates. Question is, when vacuum does rotate it, from movement, wonder if the circuit could be getting grounded out? That would turn things to crap.

Tried that too. Checked resistance before and after applying vacuum on the plate. Got the same readings both ways.

 

[Dragon Slayer]

Yes the driving test matters. In neutral it does not take much throttle opening to maintain 2500 RPM, that means it is like a Cruise no load when vacuum goes up. Under load of actual driving, throttle will be open more to maintain speed and vacuum will come down. So less Vacuum timing added.

One last thing, what did you do with mechanical springs? If you look at the specs in SVM, the light spring lets the first stage of advance come in pretty quickly, but only about 6 to 10 degrees of mechanical advance by about 1500 rpm. To get the last 18 degree of advance you have to get up about max rpm near 4600 RPM. Not something you want to do unloaded in neutral for very long. If you have all you mechanical advance in too early, coupled with full vacuum advance at 2500rpm in neutral, you would have way too much timing advance for the operating condition.

Racers and performance setup want all there advance in early, but they do not use vacuum advance, or if they do, they use a can with much less advance that only comes in at high vacuum. If your getting all your mechanical in too early, I would dial initial back to a lower initial timing value like 8, and then connect vacuum cannister and take a test drive.

 

[Fran Blacker]

Your condenser doesn't look like it has a non-conducive sleeve on it. Any chance its hitting advance arm or stud?

 

[miller]

So 12.5 mechanical advance is enough?

How did you determine that? Number of degrees the rotor will rotate?

If you have 12.5 degrees BTDC initial, plus 12.5 degrees mechanical advance, that only equals 25 degrees total mechanical.
Should be getting 34 - 36, tops 38 degrees.

You other guys correct me, if I'm wrong.

 

[67 GTX]

Yes the driving test matters. In neutral it does not take much throttle opening to maintain 2500 RPM, that means it is like a Cruise no load when vacuum goes up. Under load of actual driving, throttle will be open more to maintain speed and vacuum will come down. So less Vacuum timing added.

One last thing, what did you do with mechanical springs? If you look at the specs in SVM, the light spring lets the first stage of advance come in pretty quickly, but only about 6 to 10 degrees of mechanical advance by about 1500 rpm. To get the last 18 degree of advance you have to get up about max rpm near 4600 RPM. Not something you want to do unloaded in neutral for very long. If you have all you mechanical advance in too early, coupled with full vacuum advance at 2500rpm in neutral, you would have way too much timing advance for the operating condition.

Racers and performance setup want all there advance in early, but they do not use vacuum advance, or if they do, they use a can with much less advance that only comes in at high vacuum. If your getting all your mechanical in too early, I would dial initial back to a lower initial timing value like 8, and then connect vacuum cannister and take a test drive.

Understood. I will try driving it with some vacuum hooked up.
Attached is the pic of the springs that came with the distributor, and the ones I put back in. From what I researched, these are the stock springs.

Your condenser doesn't look like it has a non-conducive sleeve on it. Any chance its hitting advance arm or stud?

It does have the plastic/rubber sleeve around it's metal arm.

How did you determine that? Number of degrees the rotor will rotate?

If you have 12.5 degrees BTDC initial, plus 12.5 degrees mechanical advance, that only equals 25 degrees total mechanical.
Should be getting 34 - 36, tops 38 degrees.

You other guys correct me, if I'm wrong.

I tried to turn the cam by hand the other day, but it's too difficult to really determine how much it was moving.
How I got the believed mechanical advance was to set the initial timing to 0, then rev'd the motor. The amount that the marks on shown on the balancer moved was about 12.5 degrees.

 

[khryslerkid]

Is this still going on?

Too many post to go back through but I thought I read that your dwell was at 26*. I read where you set points at .010 with a feeler guage, thats too narrow. Dwell also effects timing. Whenever you change the dwell, you'll have to reset the timing.

I'm going back to the beginning.
Set your primary set of points with a dwell meter. Spark plugs removed makes cranking easier.

The primary set is the set of points that open first. Big block distributors turn counter clockwise. Find top dead center and mark the distributor housing where the rotor lines up with number one plug wire on the cap. The primary set of points will start to open here.

With a small piece of cardboard in between the second set of points, crank the engine and set the dwell to 26 degrees on the primary set. Now remove the cardboard and place it in the primary set. Crank the engine and set the secondary set to 26 degrees. Remove the cardboard, crank the engine and you should have close to 34 degrees combined dwell. If you need to change the combined dwell, only adjust the secondary set of points.

Now on to the timing.
Start the engine with the vacuum advance unhooked and plugged off. Watching your timing marks with the timing light, rev the engine until the mark stops moving. Make a note of where the mark stopped and what rpm. Lets say the mark stopped at 2,000 rpm at 20 degrees. Lets try to get it to 34 degrees. Rev the engine to 2,000 rpms again, turn the distributor till the mark is at 34 degrees. Lock the distributor at this degree. Now check the timing at idle. (You might have to adjust the carb idle, say 600 to 800 rpm).

Now whatever the timing is reading at idle is your initial timing. The "all in" timing is the 34 degrees.

Now hook up the vacuum advance. Reving the engine, watch how far the timing mark goes up the scale before it stops. Might be as high as 50 degrees. If its more it will have to be limited.

Try this and report back.

 

[Dragon Slayer]

That slot looks wide on the cam stop. Also looks like one weight is not in a slot?? So I do not know how much mechanical advance your getting. I went back and looked at the 67 specs. You get the 7 to 12 degree mechanical advance by 1600 RPM. A little earlier (lower RPM) on HP cars. Your not going to see the full mechanical advance of 17 to 21 degree until about 4400 to 4600 rpm if it tuned to the Service manual spec. Only the hemi gets all mechanical advance in at a much lower rpm 2800 for a 67 hemi. Nothing wrong with lightening up the springs to get the advance in earlier for performance, but you really need to know how much full mechanical you get. If you have the later year CAP type cam stop your going to get a full mechanical advance of between 25 and 29 degrees (Autos) and you can't have initial much above 5 with that combo, and then your vacuum will only complicate your problem. Would really like to see the numbers on the bottom of cam stop.

I would set your timing at 5 and connect vacuum and take a test drive. If no pings at WOT or at high RPM and your only problem is some bogging or stumble, you can increase initial timing incrementally, and see if it clears up. If it does ping you have too much timing and you have to figure out why. I am hoping your test drive is good.

 

[khryslerkid]

That slot looks wide on the cam stop. Also looks like one weight is not in a slot?

I agree.

 

[67 GTX]

I will test all of these things out in the coming days and report back to you all.

I should've noted on the pic of my cam stop. That isn't how I installed it, just a pic I took for reference upon initial disassembly. The stops are held in the cam.

 

[67 GTX]

Is this still going on?

Too many post to go back through but I thought I read that your dwell was at 26*. I read where you set points at .010 with a feeler guage, thats too narrow. Dwell also effects timing. Whenever you change the dwell, you'll have to reset the timing.

I'm going back to the beginning.
Set your primary set of points with a dwell meter. Spark plugs removed makes cranking easier.

The primary set is the set of points that open first. Big block distributors turn counter clockwise. Find top dead center and mark the distributor housing where the rotor lines up with number one plug wire on the cap. The primary set of points will start to open here.

With a small piece of cardboard in between the second set of points, crank the engine and set the dwell to 26 degrees on the primary set. Now remove the cardboard and place it in the primary set. Crank the engine and set the secondary set to 26 degrees. Remove the cardboard, crank the engine and you should have close to 34 degrees combined dwell. If you need to change the combined dwell, only adjust the secondary set of points.

Now on to the timing.
Start the engine with the vacuum advance unhooked and plugged off. Watching your timing marks with the timing light, rev the engine until the mark stops moving. Make a note of where the mark stopped and what rpm. Lets say the mark stopped at 2,000 rpm at 20 degrees. Lets try to get it to 34 degrees. Rev the engine to 2,000 rpms again, turn the distributor till the mark is at 34 degrees. Lock the distributor at this degree. Now check the timing at idle. (You might have to adjust the carb idle, say 600 to 800 rpm).

Now whatever the timing is reading at idle is your initial timing. The "all in" timing is the 34 degrees.

Now hook up the vacuum advance. Reving the engine, watch how far the timing mark goes up the scale before it stops. Might be as high as 50 degrees. If its more it will have to be limited.

Try this and report back.

Yes, the .010 gap gave me 26*. I did exactly as you said. .010 on each set of points gave me 26* on each, and a combined dwell of (at the time) 38*.

For me to get the 34 degrees (without the vacuum advance), I would have to set the initial timing to somewhere around 20* BTDC. Here is the other interesting thing, the car used to start great (with the old distributor) set to an initial timing of 12.5 BTDC. Now, with the exact same initial setting, with the dual point distributor, the car doesn't start as quickly. Not sure why.

And the problem is I am not able to rev the motor up with vacuum hooked up (starts knocking out around 13-15 in hg) when placing a vacuum handheld pump on the vacuum advance. This occurred even when I set my initial to 20ish.

Would really like to see the numbers on the bottom of cam stop.

I would set your timing at 5 and connect vacuum and take a test drive. If no pings at WOT or at high RPM and your only problem is some bogging or stumble, you can increase initial timing incrementally, and see if it clears up. If it does ping you have too much timing and you have to figure out why. I am hoping your test drive is good.

If I ever pull it apart again (which is looking like a solid chance), I'll be sure to grab some more pics of everything.

I will give that a shot, can't hurt.

One thing I have noticed, when driving with the vacuum not hooked up, I can hear a slight ticking coming from the motor when driving. But if I put the motor in neutral and rev it up, I don't hear any ticking. Perhaps this ticking is a very low level ping? Seems in line with engine load. But, and correct me if I'm wrong, pinging usually occurs if you are over-advancing, not under-advancing (which I believe we have all but determined that my distributor is doing).

 

[khryslerkid]

Yes, the .010 gap gave me 26*. I did exactly as you said. .010 on each set of points gave me 26* on each, and a combined dwell of (at the time) 38*.

I would like to see 30*- 34* total on the dwell. Maybe use .015 - .017 gap on the points.

38* dwell is a little close (narrow). The higher the dwell number, the closer the gap.

For me to get the 34 degrees (without the vacuum advance), I would have to set the initial timing to somewhere around 20* BTDC.

So the distributor is making 14* mechanical. I'm thinking if you open your points a bit more you might see a larger degree spread on the timing. Then you might be able to set the initial to 16* - 18*. If it doesn't like it there you'll have to find the sweet spot by experimenting. Get this close and you can move on to the vacuum advance.

 

[67 GTX]

I would like to see 30*- 34* total on the dwell. Maybe use .015 - .017 gap on the points.

38* dwell is a little close (narrow). The higher the dwell number, the closer the gap.



So the distributor is making 14* mechanical. I'm thinking if you open your points a bit more you might see a larger degree spread on the timing. Then you might be able to set the initial to 16* - 18*. If it doesn't like it there you'll have to find the sweet spot by experimenting. Get this close and you can move on to the vacuum advance.

I will give this a shot. From what I remember, when I had the gap set to more closer to spec (.017), I couldn't get the car to run. But their might have been other issues then that I can't fully recall right now.