Need Dual Point Assistance

[miller]

Another dumb question...on that Prestolite. How many lobes on the cam, four or eight?
I've been reminded (another post/site), like on the Mallory RevPol, four lobe, I had in the past, point gap is .018. Eight lobe cam, .020 point gap, to reach the correct dwell.

 

[Fran Blacker]

Does the distributor have the jumper wire from one set of points to the other?

 

[khryslerkid]

Does the distributor have the jumper wire from one set of points to the other?

Here's the way the Mallory is set up.

 

[Fran Blacker]

Presolites the pigtail from coil has a wire that goes one set of points then to the second set. Just somebody cut it off or put a single point pigtail, this is a long shot but put out there.
Some interesting experiences posted.

 

[67 GTX]

I believe my lob was the normal 8 sided one

*Update*
After reading all your posts, I decided to pull the distributor out again and check everything. I replaced the condensor just to play it safe, and cleaned the points again.
Could have been some corrosion still showing on the points.

I gapped the points at .010, and that actually gave me a good dwell of 40. I'm not sure why every set of points I've done hasn't been in-spec with the gap, but gives me the correct dwell?

Either way, the car is running now. I used to have a mopar aluminum distributor on it, and I would always run the vacuum advance (carb. vacuum is only available from the 4326s carb I believe) with an initial timing of 12.5 BTDC (set without vacuum advance)), and the car would run fine.
But with this new distributor, I had to block off the vacuum advance, and lower the initial timing (12.5 was fine in the street, not too happy on the highway), so I lowered it to 10 now.

I guess this new distibutor has a more severe curve? I did confirm that I did have the normal springs on the weights. Couldn't confirm if the vacuum advance spring is original, but I believe that it is.

 

[HALIFAXHOPS]

Glad to hear it is running. What vac advance spring? The part that has the cam lobes on it should have a number on it by the slots for the weights. That number tells you what the max advance for the mechanical side of the advance is in distributor degrees. What do you thing the problem was?

 

[HALIFAXHOPS]

Should have asked this a while ago what are the tag numbers on the distributor?

 

[67 GTX]

The cast iron dizzy has an adjustable vacuum advance where a removable spring presses against the diaphragm.
Is the number you are referring to an actual number? Just off memory, I only recall seeing an E by one of the weight openings.

Well the book calls for 0 initial timing, so I gave that a shot. 0 initial with the vacuum advance hooked up, the car stumbled in neutral when reving it at idle. This issue stops once you disconnect the vacuum advance. I did test it to make sure it works, and that it wasn't leaking.

The tag on the distributor reads: CHRYSLER 2642899
IBS 4006 Z 46 6

I thought full advance comes in around 2000-2500 rpm, so I'm not sure why the car seemed ok then, but not above 3000 rpm.

 

[HALIFAXHOPS]

OK older vac advance any small washer looking shims in there on the end of the spring where the nipple goes on? And also how tense is the spring? Kind of light? Could be not enough spring tension on the diaphragm. That regulates where the vac advance will be in what setting of vacuum at the time. Now that makes sense.

 

[HALIFAXHOPS]

67 where in NY are you if close bring it by and we can run it on a machine and figure it out. I am N of Harrisburg, PA

 

[67 GTX]

OK older vac advance any small washer looking shims in there on the end of the spring where the nipple goes on? And also how tense is the spring? Kind of light? Could be not enough spring tension on the diaphragm. That regulates where the vac advance will be in what setting of vacuum at the time. Now that makes sense.

Yes, i have a washer below the nipple. The spring is actually tense (I have to compress it some with some force in order to get the nipple to thread on). So I guess I would need an even stiffer spring to delay or lower the vacuum advance?

Thanks for the offer. I believe you are a bit of a trip from me in Brooklyn. Do you have a distributor machine? Like an old sun one?

*Update*
Last night I tried driving the car with initial timing at 10 BTDC, and still had similar issues. I then dropped it down to 5 BTDC, and it did seem better. This is leading me to believe that I had the car over-timed, just not sure why now with the dual point it doesn't like more initial timing.

 

[HALIFAXHOPS]

I have a few sun testers. I do distributor rebuilding. Hey was the timing chain ever changed? Wondering if possibly that some one put it advanced. Just a thought. You have a weird on going on. I am originally from LI, definitely miss the food.

 

[khryslerkid]

Sounds like maybe useing a piston stop would help you to determine where your timing is and it helps to verify your mark on the dampner.

 

[67 GTX]

The timing chain is new and was checked again about 2000 miles ago.

There's a few things I don't understand from the swap:

I didn't touch the carb at all. I got the car running with the new dizzy, and the idle was 300rpm lower than before.

Is the gap or dwell the final setting that you are shooting for with points? I have never been able to set the gap as per spec and get the spec'd dwell.

My older dizzy (it has a forward look stamp on it so I guess it's pre-65?) was always set at 12 BTDC initial timing with the vacuum advance hoooked up (I believe the 4326s carb only has carb. vacuum available) and the car ran great. Now it only runs good with initial timing at 5 or less, without the vacuum advance hooked up.

I believe I have a stock cam as well.

Does anyone know why these things happened?

 

[miller]

Is the gap or dwell the final setting that you are shooting for with points?

Okay...the final setting would be dwell...for THAT distributor. Should have numbers to shoot for, per the book. But, you might be missing a few things.
New timing chain? Was it installed correctly, timed? Guessing yes, but you should check the basics on it.
If you pull the distributor (not dizzy)(yeah, I know, again!), and look in the hole, you can see the two lifters for #1 cylinder. Why? Turning the engine over by hand, you can check for TDC compression stroke, piston on top, both valves closed (by the lifters), timing mark on the dampner, all that you need to know, to make sure things are right.
Timing mark at 0, piston should be at top, both valves closed. If not, timing is off.

Should know how much advance is 'set' in the distributor, degrees, so when advance is 'all in', it's still in range 34-36. Think that's right, maybe up to 38. Knowing how much advance, minus the full advance, tells you about where the initial should be. Such as full advance at 35, 20 degrees advance in the distributor, gives 15 initial setting.
Usually, both sets of points are set the same, with a feeler gauge, then check dwell, both for each point set, then total. Always worked for me.

 

[67 GTX]

I did get both points in spec for the dwell when tested on their own (by blocking the other), and the total dwell for both also fell within the spec.

Good idea for checking TDC.

Based on that I can only assume this distributor has more total advance, and maybe even it comes in earlier, than the other distributor that I was running.
Still confused as to why it doesn't want the vacuum advance hooked up, when everything is set to the spec that the book calls for.

 

[oldbee]

MAYBE ur losing ur ground on the plate the points are mounted when v.adv kicks in? Could be something else too. If you ever had a chance to use a Sun dist.machine!!!!! Had one for awhile & did every points change with it,even for a run-of-mill customer tuneup; just so easy to get dwell,etc., set up with no bending over a fender.

 

[HALIFAXHOPS]

You want send it to me and I can check it! Have 5 sun distributor testers!

 

[miller]

Based on that I can only assume this distributor has more total advance, and maybe even it comes in earlier, than the other distributor that I was running.

That is probable, between the two different distributors. Should be able to adjust advance amount/rate, to match what you had, or want, provided the springs can be found.

Vacuum advance...might do a search, here on the site. There's several great discussions about it, might find answers you want.

 

[67 GTX]

MAYBE ur losing ur ground on the plate the points are mounted when v.adv kicks in? Could be something else too. If you ever had a chance to use a Sun dist.machine!!!!! Had one for awhile & did every points change with it,even for a run-of-mill customer tuneup; just so easy to get dwell,etc., set up with no bending over a fender.

Anything is possible. I did clean that plate very thoroughly, and made sure the grounding wire was in good working order.

Only thing I don't have to spec, is my spark plugs. I have a set of 12s in it now, but the car calls for 11s (which I will install). Although I can't imagine that slight difference makes the difference here.