Carter AVS Part 2 on the car tuning

[HS 69 Charger]

Hi Guys, Thanks again for more information.
@Geoff 2
Here is a pic of the Distributor. This is the distributor that came from the Mopar Electronic Ignition upgrade kit P3690427. That kit came with the distributor, Orange ECU P4120505 and Ballast Resistor P5206436. It was purchased in 1988. I should also note the Coil is original stock. After years of cleaning for car shows the white part number is gone so I can't confirm the number.
It does appear to have the hex portion at the nipple but not sure how that makes it adjustable. If it is then will wait for your extra information.
If it is NOT adjustable then I would need information on the option of converting/adding an adjustable vacuum advance. Also you said decision time but you didn't really say what the option is if I don't go to an adjustable vacuum advance.

Thanks again for all the help and suggestions,

Martin

 

[HS 69 Charger]

@AR67GTX
I have not really done anything with this distributor. As noted above it is the "stock electronic" distributor sold back in the 80s. No customization has been done since then. I also have not done any testing (documenting) of the timing at higher speeds. I am going to need to add some kind of extender on the timing mark plate as the stock one only goes to about 20 and everything beyond is an eyeball estimate. Also, my 1980s tools (timing light and tachometer) are struggling so I am going to need to get a new Timing light with the rpm built in to make this more doable. I feel like I need a bit more precision to take this step.
Lastly, on the pre detonation/pinging, I was thinking I could roll back the Timing/idle adjustment and see if it is diminished and or eliminated to help verify this is what is happening. But all of this seems to be worth doing to more accurately diagnose this symptom.
Oh, I have moved to 91 no ethanol fuel. I ran my tank nearly dry and then switched over so I am pretty pure at this point.

 

[Geoff 2]

Martin,
[1] Ethanol fuel causes corrosion in the carb because it absorbs water. So wise move using non-E fuel.
[2] That VA unit should be adjustable. To check, get a 3/32" Allen Key & put in the nipple hole. If it engages, try turning it L or R. If it moves, it is adjustable & not frozen up.
[3] Let us assume at this stage that it adjusts [2]. Once verified that it does, we go the next step. Just FYI, the AK movement compresses a spring inside the VA unit, & is part of the actuator arm of the VA unit. Since vacuum is being applied to the VA unit, the spring tension has control over movement of the actuator arm.

 

[HS 69 Charger]

I inserted the Allen Key and yes it fits and does turn both directions. So next step.

 

[HS 69 Charger]

Latest Update:
First, I entered the 21st century and picked up an Innova 3568 Timing light so I could see the rpm and use the Adv feature and get exact Timing measurements. Both show on the display simultaneously. What a dream. But was hard to let go of the Tach/Dwell meter and timing light I've had since I was 17. Ok I'm over it. Man is the Innova nice.
So with real tech in hand here are much more precise measurements, plus a timing vs RPM (centrifugal Advance), and a confirmation of vacuum advance.
And then at the end of the tests I backed off the timing at idle by 3* and retested drive acceleration for pre-detonation. And it seems gone. And I still have good acceleration with no stumble.
This is the best the car has driven in a long long long time. Very drivable, but I am concerned about high end timing and did not test at Interstate speeds yet until we confirm if that should be backed off. All tests so far were at 45-50mph and from stop or low speed acceleration.

So here is the data:
Park: rpm 810-830 Timing 31* with 2-3 var and Vac 17"
Drive: rpm 650 - 660 Timing 31* with 3-5 var and Vac 14"
Vac Advance removed: No change on Drive values
Remember idle screw position is about 020 transition line

Now with Vac Advance still off I did rpm vs timing curve
650 and 830 were 31*
1200 38*
1500 46*
1750 53*
2000 56*
2250 56*
Seems I have fairly light springs on the distributor as I'm all in by 2000. Is that also why its so bouncy?

Last backoff of idle timing from 31* to 28*
Lost about 25rpm and a bit of vacuum
Idle 630rpm timing 28* and vacuum still 14"
Added Vac Adv back on and no change. Is this because the idle position is now down to 020?
I should state, I did not change the idle position, the idle fuel screws, or the allen key vac advance. Only timing by turning distributor.

Obviously, I am mostly thrilled as the car is very drivable right now.
Concerns are overall total timing seems high. (with backoff it should be 53*). Should I be wary at highway speeds until addressed which may be Geoff's plan on next step.
The bouncy timing. Which might also correlate to the overall "miss/hesitation" feeling that I sense when driving.

Thanks again for all the help as again this is a huge transformation of how it drove before.
Martin

 

[Geoff 2]

I am wondering if the VA init is actually working....
Remove the dist cap. With VA hose connected to the VA unit, suck on the hose. You should see the plate in the dist move.

 

[HS 69 Charger]

I had previously tested the VA unit with a hand pump/gauge and it was working. I did test this yesterday as well and it was fine.
8" vac (from pump) Timing 35*
15" vac Timing 47*
Originally at idle it made a difference when connecting/disconnecting from the carburetor. But after all our adjustments with idle position (020 slot)/idle mixture screws now at idle it does not change when connected/disconnected. I did not tee in my vacuum gauge to this line to see what it is reading with the idle position down at 020.

 

[HALIFAXHOPS]

Thats a mopar performance dist that came with the kit. Seriously fast advance usually all in by 15oo rpm. I had springs made to slow it down for the street if needed.

 

[AR67GTX]

Latest Update:
First, I entered the 21st century and picked up an Innova 3568 Timing light so I could see the rpm and use the Adv feature and get exact Timing measurements. Both show on the display simultaneously. What a dream. But was hard to let go of the Tach/Dwell meter and timing light I've had since I was 17. Ok I'm over it. Man is the Innova nice.
So with real tech in hand here are much more precise measurements, plus a timing vs RPM (centrifugal Advance), and a confirmation of vacuum advance.
And then at the end of the tests I backed off the timing at idle by 3* and retested drive acceleration for pre-detonation. And it seems gone. And I still have good acceleration with no stumble.
This is the best the car has driven in a long long long time. Very drivable, but I am concerned about high end timing and did not test at Interstate speeds yet until we confirm if that should be backed off. All tests so far were at 45-50mph and from stop or low speed acceleration.

So here is the data:
Park: rpm 810-830 Timing 31* with 2-3 var and Vac 17"
Drive: rpm 650 - 660 Timing 31* with 3-5 var and Vac 14"
Vac Advance removed: No change on Drive values
Remember idle screw position is about 020 transition line

Now with Vac Advance still off I did rpm vs timing curve
650 and 830 were 31*
1200 38*
1500 46*
1750 53*
2000 56*
2250 56*
Seems I have fairly light springs on the distributor as I'm all in by 2000. Is that also why its so bouncy?

Last backoff of idle timing from 31* to 28*
Lost about 25rpm and a bit of vacuum
Idle 630rpm timing 28* and vacuum still 14"
Added Vac Adv back on and no change. Is this because the idle position is now down to 020?
I should state, I did not change the idle position, the idle fuel screws, or the allen key vac advance. Only timing by turning distributor.

Obviously, I am mostly thrilled as the car is very drivable right now.
Concerns are overall total timing seems high. (with backoff it should be 53*). Should I be wary at highway speeds until addressed which may be Geoff's plan on next step.
The bouncy timing. Which might also correlate to the overall "miss/hesitation" feeling that I sense when driving.

Thanks again for all the help as again this is a huge transformation of how it drove before.
Martin

Martin, that quick advance curve is not what I expected you to find in the distributor but you never know what a previous owner has done. Like Halifaxhops said, it would be a good idea to slow it down a little some day but if it’s running good right now there’s no hurry.

A bouncy timing can be a couple of things. Could be the light advance springs letting the weights dance around with small rpm changes. On GM distributors I found that excess distributor shaft movement (up/down) in the housing caused nervous timing. Shimming the shafts largely to about .006-.008” usually eliminated it. Mopars may suffer from the same but I haven’t played around with it as much. Worn distributor housing bushings also can cause erratic timing marks but I would doubt your replacement distributor has that much wear. You can try wiggling it back and forth by grabbing the rotor and you shouldn’t feel much, if any, lateral movement.

Glad you like the Innova timing light. The one thing I accidentally found out about mine is the clamp for the plug wire is not very heat tolerant but as long as you keep it away from the exhaust manifolds it’s fine.

 

[HS 69 Charger]

Thanks for the confirmation @HALIFAXHOPS so I didn't lose my mind.
@AR67GTX I am actually the one who did the electronic kit install back in 1988. So its pure factory kit and no changes have been made.

Before I hit the interstate speeds, I did want to make sure the Total timing is not too much (would be about 53* after the 3* backoff). I just want to make sure I'm not hurting anything.

As to next steps, am waiting to see what @Geoff 2 suggests as his carb tuning advice has been very helpful.
I do think following up on the Distributor as my next project is worthwhile but probably about a month down the road as I am out of town and have a couple items diverting me from the car. Plus I can drive the car now (unless something is still needed on the high total timing for safe operation).
I have seen other threads that start off with this high timing and then add a limiter into the distributor to bring down the total timing. So instead of a full 25* curve its down to 15* or so. They also seem to select/change the springs to get the curve in the rpm range they want. I will need advice on that when I get there. I will probably start a new post on the distributor under the Electrical & Ignition forums. Bottom line is I think the Distributor is my next project.

Just looking for thoughts on high total timing and Geoff's comments to finish this one (or maybe I should say the initial part of this one) so I can test drive for awhile.

 

[68-500]

Are you sure you’re using the dail back light correctly? With 5* initial there is almost no way you should have 56* total mechanical advance . Unless you have VA in use. You should set your daily to 34-36 un plug VA, then rev engine to say around 2-2500 rpms and adjust distributor to may indicator on dampener read zero. Lock down distributor then you can play with adjustments in the VA to get your desired idle quality/ speed.
I reread some more of your posts if you find after setting your total MA to say 34-36. And after adjusting VA If you cannot achieve your desired advance at idle you will need to limit the amount of MA built into distributor. By doing that you can raise your intial advance and still maintain your 34-36 total MA.

 

[HS 69 Charger]

@68-500 There have been lots of posts so easy to get off. the 5* initial was basically where I started which was by the book before I got anywhere. Geoff then walked me through the Idle Mixture Screws, Idle screw (noting the actual transition slot length), and then idle level timing which is 28*. He is working with me on next step which I believe will involve further adjustment for both Idle and Total Timing.
I believe your process starts at the Total and then comes back to the idle and his starts at the idle. I don't want to mix things up so for this part I will wait on his next step.

Thanks for your comments as it does give me a sense of total timing.

 

[68-500]

I see I thought you was getting nearly 50* mechanical timing. Carry on.

 

[Geoff 2]

Hi Martin,
I couldn't log onto the site y'day for some reason, back now.
Next step.
The Chry VA units usually have a number stamped on the arm, eg 11.5. That means the the unit advances the timing 11.5 dist degrees, which is 23 crank degrees. All the numbers I will be talking about are in crank degrees.
- check the number on your VA unit
- I think I read earlier in the thread that the init timing [ no VA ] was 5*? Whatever the factory timing is for initial, you should use that.
- the sweet spot you found for idle timing was 31*.
- I will wait for you to confirm the number on the VA actuator arm & the factory initial timing.
- are you using [a] factory air cleaner is the air inlet to it a snorkel type device?

 

[Some Car Guy]

What is your total timing at with no vacuum advance? If it’s more than mid 30s, this won’t end well.

 

[Some Car Guy]

Talking further over pm, the engine has over 50 degrees total without vacuum advance and is most certainly being damaged. It is very important for total to be discussed on this topic as doing testing of any sort where total without vacuum goes over about 38 you will undoubtedly be seeing preignition and/or detonation.

My own experience and according to mopar action, best power with stock chamber big block mopar heads will be at 33-35 total and I typically shoot for 34. You work backward from there to set the initial and rate, not start in the basement and work up.