Need Distributor Specifications

[67 GTX]

Hello all,

I re-installed the original cast iron dual point distributor on my 67 GTX. It is a 440 4-speed car.

When going through the FSM specifications, it does not give any specs for a dual point.

The tag on the distributor says:
CHRYSLER 2642911
IBS-4006-Y 67

Does anyone have any info on this? I am looking for the spec sheet that shows things like it's advance, points gap, dwell angles?

Dwell angles are really what I need right now. Seems the FSM shows 28-32 degrees for a single pt 440, and 27-32 (37-42 total) for a hemi. Not sure if those specs apply to mine.

Thank you

 

[pnora]

Specs for the most are identical for the points settings. Gap .014 to .019, Dwell individual 27 to 32 ,, Both 37 to 42

 

[RJRENTON]

I have an origional Prestolite dual point distributor in my RS23V0A****** 1970 GTX 440 six barrel 4 speed car. I use either Mopar NOS points or Standard Blue Streak set at 0.016" (both sets ...set independently). The static timing is ~ 15° initial (idle) and 20° centrifugal, all in by 2400 RPM for a total advance of 35° at 2400 without vavuum advance. This is what works for me.....
Consider @HALIFAXHOPS for your NOS ignition system requirements.....an excellent source. He is usually at the Chryslers at Carlyle show this month.
BOB RENTON

 

[Beekeeper]

@HALIFAXHOPS

 

[HALIFAXHOPS]

Those are the dwell specs you use for a Dual point. Set each set of points to the single speck then both should be 38-42.

 

[67 GTX]

Thanks guys. I thought the primary set is set to single point specs, and then the secondary set are set to whatever gives the correct total dwell? So both may not be the same gap.

 

[pnora]

Thanks guys. I thought the primary set is set to single point specs, and then the secondary set are set to whatever gives the correct total dwell? So both may not be the same gap.

Nope both the same. I gave up on dwell years ago. As RJ said .016 on both and let her rip. Dwell is deceiving with worn lobes and shaft bushings.

 

[67 GTX]

I could use your guys assistance here:
Below are the timing settings from the single pt that I took off, and the dual pt that I put on.

Including vacuum advance, should the total timing be around 34 degrees?
When figuring out total timing, isn't that initial + mechanical advance + vacuum advance?

The dual pt. has the VA where the nipple can be unscrewed. To limit it's advance, do I just have to stiffen up the spring? I've read on here about there is a 3/32" adjustment screw?

Single pt
RPM Adv (wo/w VA)
Idle 12/12
1500 23/36
2000 23/36
2500 23/36
Dwell: 26 degrees

Dual pt
RPM Adv (wo/w VA)
Idle 12.5/12.5
1500 23/42
2000 24/44
2500 24/50 (hooking vacuum up here jumped rpms up another 400 rpm)
Total Dwell: 26 degrees

 

[pnora]

I could use your guys assistance here:
Below are the timing settings from the single pt that I took off, and the dual pt that I put on.

Including vacuum advance, should the total timing be around 34 degrees?
When figuring out total timing, isn't that initial + mechanical advance + vacuum advance?

The dual pt. has the VA where the nipple can be unscrewed. To limit it's advance, do I just have to stiffen up the spring? I've read on here about there is a 3/32" adjustment screw?

Single pt
RPM Adv (wo/w VA)
Idle 12/12
1500 23/36
2000 23/36
2500 23/36
Dwell: 26 degrees

Dual pt
RPM Adv (wo/w VA)
Idle 12.5/12.5
1500 23/42
2000 24/44
2500 24/50 (hooking vacuum up here jumped rpms up another 400 rpm)
Total Dwell: 26 degrees

Your total dwell is quite a bit off. I would adjust each set separately blocking the other set open for each setting. the total dwell should be 37-42

 

[AR67GTX]

Most people ignore vacuum advance when discussing total timing since it goes to zero under acceleration. Your base timing and centrifugal advance timing should be in the range of 34 to 36 degrees typically. For whatever reason my 440 GTX likes 33 - 34 and pings on any more than that. Your vacuum advance is only a factor at idle ( if connected to full vacuum) and steady state cruise. Too much vacuum advance can create too much of a good thing at highway cruise when all three come into play together and can boost your timing to around 50+ degrees. This can cause a missing or slight trailer hitching sensation which is easy to diagnose by temporarily plugging it for a test drive. The solution is to find a vacuum can with less advance or rig up a stop to keep it from fully activating.

 

[67 GTX]

Your total dwell is quite a bit off. I would adjust each set separately blocking the other set open for each setting. the total dwell should be 37-42

Agreed, that is next on my list, but that shouldn't be affecting my timing characteristics right?

Most people ignore vacuum advance when discussing total timing since it goes to zero under acceleration. Your base timing and centrifugal advance timing should be in the range of 34 to 36 degrees typically. For whatever reason my 440 GTX likes 33 - 34 and pings on any more than that. Your vacuum advance is only a factor at idle ( if connected to full vacuum) and steady state cruise. Too much vacuum advance can create too much of a good thing at highway cruise when all three come into play together and can boost your timing to around 50+ degrees. This can cause a missing or slight trailer hitching sensation which is easy to diagnose by temporarily plugging it for a test drive. The solution is to find a vacuum can with less advance or rig up a stop to keep it from fully activating.

I was noticing that when reading through the forum. I am having a hard time fully understanding what total timing is and how to tune to it.

Seems that my initial + mechanical advance isn't enough, and my vacuum advance is too much?
Do you run vacuum advance?
And what advance do you want under a steady cruise?

 

[AR67GTX]

Yes, I have four cars with old motors and when I can I run full time vacuum advance. I have an old Ford with a non vacuum advance distributor and a mopar with only ported vacuum advance off the AFB that are exceptions. Do all your timing adjustment with vacuum advance plugged off but hook it up to adjust carb mixture needles.

How much is too much vacuum advance is difficult to answer and depends on the details of the motor. If the distributor has a lazy factory centrifugal timing curve that doesn’t come in all the way until 4000 rpm or higher then you probably can just run a factory vacuum advance and forget it. If you have a lot of compression, a distributor modified for 16 - 20 degrees base timing and a quick advance curve that comes in around 2000 rpm, you’re probably going to have issues with a factory vacuum advance can and some pinging and trailer hitching. In that case you will need to somehow limit the amount of vacuum advance.

But, at least for me, vacuum advance is good on the street as the additional advance helps cool the engine. But if you recurve the distributor to run 16 - 20 degrees of base timing and with a quick advance curve, it becomes less important.

 

[pnora]

Agreed, that is next on my list, but that shouldn't be affecting my timing characteristics right?


I was noticing that when reading through the forum. I am having a hard time fully understanding what total timing is and how to tune to it.

Seems that my initial + mechanical advance isn't enough, and my vacuum advance is too much?
Do you run vacuum advance?
And what advance do you want under a steady cruise?

Point setting does affect timing. I would get that first and then reset the timing. I would base tune it with no vacuum advance. Once the base and mechanical are good and the car starts good I would tune in the vacuum.

 

[67 GTX]

Yes, I have four cars with old motors and when I can I run full time vacuum advance. I have an old Ford with a non vacuum advance distributor and a mopar with only ported vacuum advance off the AFB that are exceptions. Do all your timing adjustment with vacuum advance plugged off but hook it up to adjust carb mixture needles.

How much is too much vacuum advance is difficult to answer and depends on the details of the motor. If the distributor has a lazy factory centrifugal timing curve that doesn’t come in all the way until 4000 rpm or higher then you probably can just run a factory vacuum advance and forget it. If you have a lot of compression, a distributor modified for 16 - 20 degrees base timing and a quick advance curve that comes in around 2000 rpm, you’re probably going to have issues with a factory vacuum advance can and some pinging and trailer hitching. In that case you will need to somehow limit the amount of vacuum advance.

But, at least for me, vacuum advance is good on the street as the additional advance helps cool the engine. But if you recurve the distributor to run 16 - 20 degrees of base timing and with a quick advance curve, it becomes less important.

Thank you. I have the original carb as well, which I believe only has ported vacuum. When reading the FSM, the dual pt for a 440 isn't listed. Only the hemi shows a dual pt. in the manual, so I am looking at those specs (I know it's not apples to apples).

I wonder if I have to set my initial timing at tdc to lower the overall advance, but the motor seems much happier with a 12 degree initial setting.

Point setting does affect timing. I would get that first and then reset the timing. I would base tune it with no vacuum advance. Once the base and mechanical are good and the car starts good I would tune in the vacuum.

Thank you. I will get the points set and recheck the advance and report back.
Anything I should do to turn it further before I get to the vacuum advance?

 

[pnora]

Thank you. I have the original carb as well, which I believe only has ported vacuum. When reading the FSM, the dual pt for a 440 isn't listed. Only the hemi shows a dual pt. in the manual, so I am looking at those specs (I know it's not apples to apples).

I wonder if I have to set my initial timing at tdc to lower the overall advance, but the motor seems much happier with a 12 degree initial setting.



Thank you. I will get the points set and recheck the advance and report back.
Anything I should do to turn it further before I get to the vacuum advance?

Not really. Getting the points 100 percent is critical and a required base tuning aspect. Base timing most are happy in the 10 to 12 degree setting. RPM'S have to be low enough to keep the mechanical advance out. Once the base is set then see what your total will be base and mechanical. Lots of cars do not like much more base timing as hot start issues can show up. Once you get that part working well you can play with adding vacuum advance.

 

[AR67GTX]

I thought the 440 with a 4 speed came with a dual point but I may be remembering incorrectly. I built a dual point for my GTX (auto). I put a FBO advance limiter plate in the car to limit centrifugal advance to 18 degrees (at the crank) and run 15 - 16 degrees initial timing. I have aftermarket springs in the advance but I used some stiff enough to hold off advancing until above 1,000 rpm - not sure where it all comes in but with an auto I don’t try for a real fast advance. Halifaxhops has some Mopar Performance brand spring sets that may be a good choice. I have a couple of sets but have not had time to try them yet. The FBO advance plate is a reall great tuning item for Mopar distributors - I highly recommend it.

https://www.google.com/url?sa=t&rct...odilipl.html&usg=AOvVaw0XVoPaGNPIrF5DFd49FMJ4

 

[67 GTX]

Not really. Getting the points 100 percent is critical and a required base tuning aspect. Base timing most are happy in the 10 to 12 degree setting. RPM'S have to be low enough to keep the mechanical advance out. Once the base is set then see what your total will be base and mechanical. Lots of cars do not like much more base timing as hot start issues can show up. Once you get that part working well you can play with adding vacuum advance.

I reset both points to .016 today. I then re-did my previous measurements:

Dual pt
RPM Adv (wo/w VA)
Idle 13/13
1500 25/44
2000 26/42
2500 24/47
Total Dwell: 27 degrees
Dwell seems a bit low, at least according to the specs for a dual point.

Then I wanted to try and get total advance to 34 degrees, so I adjusted for that using my dial back timing light. After doing that at 2500 rpm, this gave me an initial timing of TDC.

Car definitely seems to want more initial timing, as idle is rougher. But then it'll put me way out over advancing if I add in some initial timing.

After driving the car around, it seemed down on power. One time, from a roll in first gear, going about half throttle, it slightly backfired before going, and had a huge hesitation. Other times it just took longer than usual to rev up.
In neutral, if you rev it quickly, it stumbles.

I thought the 440 with a 4 speed came with a dual point but I may be remembering incorrectly. I built a dual point for my GTX (auto). I put a FBO advance limiter plate in the car to limit centrifugal advance to 18 degrees (at the crank) and run 15 - 16 degrees initial timing. I have aftermarket springs in the advance but I used some stiff enough to hold off advancing until above 1,000 rpm - not sure where it all comes in but with an auto I don’t try for a real fast advance. Halifaxhops has some Mopar Performance brand spring sets that may be a good choice. I have a couple of sets but have not had time to try them yet. The FBO advance plate is a reall great tuning item for Mopar distributors - I highly recommend it.

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwiG-bmeq_34AhU3nWoFHeikAQUQFnoECAsQAQ&url=https://www.manciniracing.com/fbomodilipl.html&usg=AOvVaw0XVoPaGNPIrF5DFd49FMJ4

From what I have researched, 440 4-speeds got the dual points. I know that the FSM for 67 isn't always correct, but it doesn't show the dual point for a 440, only a hemi.
Thank you for that link, I've seen those. I am wondering if I will need one of those to suit my application.

 

[AR67GTX]

Setting accurate point gap by feeler gage has always been tedious for me, I can almost eyeball the gap better than I can set it by feeler gage which is another reason I always check it with a dwell meter. But if you are only getting 27 degrees dwell on both points operating, your point gaps are too wide and need to be closed down. You want to be in that 37 - 42 degree range.

Assuming your centrifugal advance curve has not started to come in at idle yet, you are only getting around 12 or 13 degrees centrifugal advance which is too low. A stock distributor would be more in the 24 to 30 degree range. Maybe the advance plate is gummed up, the springs are way too stiff, or someone has been inside it and welded up the centrifugal advance slot. Another possibility is the distributor has real light springs in it and that 13 degrees at idle is all or mostly centrifugal advance already - which would sort of jive with your comment of power timing it to 34 degrees total and ending up with 0 degrees base timing.

With the former you could run 20 - 21 degrees initial timing if your starter and battery can handle it. But I suspect you have the latter, a distributor with 34 degrees centrifugal advance And no room for base timing which is giving you an erratic idle. I would probably pull the distributor and take it apart to find out what’s going on inside or send it off to someone who can do it for you.

Your vacuum can might OK - kind of hard to tell until the rest of the timing is sorted out. Also getting the dwell corrected will alter your timing. Set dwell and then timing.

 

[67 GTX]

I’ve had this distributor apart many times now, and have gone through its parts a lot. I believe it has stock springs in it, but is there any indicator I should look for if I pull it apart again?

I’ll try to adjust the gaps to get the dwell up.
If to get the dwell up I close the gaps to beyond the spec, should I favor gap over dwell more if I had to choose?

 

[Geoff 2]

Dwell in a points system is a compromise. Changing dwell will not be felt by the butt meter at lower speeds, assuming the timing is correct.
Dwell is misunderstood by many. It is an angular measurement, not a time measurement. 34* of dwell refers to 34* of crank rotation. At 2000 rpm, it takes twice as long in time to for the crank to rotate as it does at 4000 rpm.
So less time for the coil to charge at higher rpms with lots [ 8? ] cyls to fire, but plenty of time at lower rpms. Too much dwell heats up the coil at lower rpms & too little dwell can cause top end misfire. That is why a compromise amount is used.