Anyone ever disassemble a distributor - need help

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Any of you ever swap that slotted mechanism ? The bottom of spare distributor says 11 degrees. I don’t know if all Chrysler small blocks are degreed the same ? Or if the degrees changed from different size small blocks, year, model, etc ? I’m bout to remove the one on the car in next few hours.
 
pearljam724 said:
Any of you ever swap that slotted mechanism ? The bottom of spare distributor says 11 degrees. I don’t know if all Chrysler small blocks are degreed the same ? Or if the degrees changed from different size small blocks, year, model, etc ? I’m bout to remove the one on the car in next few hours.
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Swapped 'em, welded and brazed and filed 'em.
No they are not all the same.
That's 11 degrees of distributor advance, 22 at the crank. It will be a little less on the engine unless running points.

The amount of advance depended on the engine configuration and what clean air package it had, if any.
11 in a electronic distributor is nice for a slightly hotter cam and no pollution control.
 
Mattax said:
Swapped 'em, welded and brazed and filed 'em.
No they are not all the same.
That's 11 degrees of distributor advance, 22 at the crank. It will be a little less on the engine unless running points.

The amount of advance depended on the engine configuration and what clean air package it had, if any.
11 in a electronic distributor is nice for a slightly hotter cam and no pollution control.
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I’m not going to mess with that piece. I don’t know where the spare came from. But, it says 11 R for right rotation. The one on my current distributor says 15 L for left rotation. I about have it back together. Is there a trick to reinstall that little clip ? I also found in a video, when you swap to a lighter spring. You should plug vacuum canister. Is that right ?
 
If its a straight slot, as far as I can tell it doesn't matter - at least on the magnetic pickup units. Some have angled slots - that's a different story then.

The spring clip. Make sure its not distorted. No I don't have any brilliant tricks. I find it is easier to install than take out. Can push it down with a flat faced punch. Move punch if it starts to ****.
 
The springs and the plates work together to provide the curve.
If you change springs may (likely) need to adjust the spring tension.

The tension on the light spring determines the rpm the advance begins.
If it begins below idle speed, it will drive you nuts.
If its too delayed, performance off the line will be hurt.

Tension doesn't apply to the secondary spring. But with it, the same adjustment to the anchor as used to adjust tension controls when the heavy spring slows down the advance. This is the critical part for good part throttle performance with vacuum advance, and also mid to top end timing.
 
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Here's some timing measurements of a DC/MP vacuum advance distributor on an engine.
Advance in Crank degrees, Engine RPM.
upload_2020-5-24_18-59-49.png

If the engine could have been idled below 900 rpm we would know if the initial timing was 12* or something less.
I suspect it was actually a couple degrees less. This particular engine would have liked 16 - 18* initial.

Anyway you can see in the timing plot how the two springs work.


We can also see it in the advance specifications in most of the shop manuals.
upload_2020-5-24_19-19-29.png


Converting the advance specifications to crank degrees and rpm, and adding to them the recommended initial timing of 10* BTC, the acceptable range on an engine looks like this
upload_2020-5-24_19-13-47.png
 
pearljam724 said:
I also found in a video, when you swap to a lighter spring. You should plug vacuum canister. Is that right ?
Click to expand...
Didn't catch this before I typed the above.
It all depends on how the curve was changed.
Generally a lighter spring is not helpful on a Chrysler except with points distrib when used for drag racing.

In general I'd say that if the advance isn't slowed down in the 1500- 2200 rpm range, then the vacuum advance will need to be delayed, reduced or disconnected.
 
This one of the places where Chrysler, Ford, AMC and the various GM engines differ enough that the 'hot setup' for one doesn't apply to another.
The pistons dwell for different lengths of time (crank degrees) at the top, the cylinder heads and pistons have different combustion characteristics, etc. As a result the rate of burn, and the time available to develop the most effective pressure through angles of maximum leverage are not going to be the same as brand X or Y.
 
Mattax said:
The spring clip. Make sure its not distorted. No I don't have any brilliant tricks. I find it is easier to install than take out. Can push it down with a flat faced punch. Move punch if it starts to ****.
Click to expand...

I hold one leg of the clip with hemostats and use a pocket type blade screwdriver to push it down.

Mattax said:
This one of the places where Chrysler, Ford, AMC and the various GM engines differ enough that the 'hot setup' for one doesn't apply to another.
The pistons dwell for different lengths of time (crank degrees) at the top, the cylinder heads and pistons have different combustion characteristics, etc. As a result the rate of burn, and the time available to develop the most effective pressure through angles of maximum leverage are not going to be the same as brand X or Y.
Click to expand...

And this is why every engine is different even from the same manufacturer, and why we can never tell someone else what their timing should be.
We can generalize, but that's about all.
 
Something tells me, I shouldn’t have tried this, we’ll see. Lol ! All I did was swap the heavy spring for an identical smaller one that was already on there. I just wanted to give it a try. But, something tells me. It’s not going to work out well. Ha ha !
 
TrailBeast said:
Not upside down, but the roll pin that locates the reluctor on the shaft can be put in the wrong slot causing a phasing issue.
The arrow and two lines is where the reluctor roll pin goes for small blocks, and the other slot in the reluctor would be for big blocks. (that way the same part can be used for either small or big blocks)
Click to expand...
upload_2020-5-24_15-42-41-png.png

So if you turn it over, you get the lefty arrow over the other notch? Thats how I remembered one I saw. I think Sheppard's book references this too. Something to check on a reman for sure.
 
pishta said:
So if you turn it over, you get the lefty arrow over the other notch? Thats how I remembered one I saw. I think Sheppard's book references this too. Something to check on a reman for sure.
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This rusty one is probably all original - still had its tag on it.
I don't recall an arrow on the bottom. But like all the ones I've seen, it has second slot - just no stamp.
upload_2020-5-24_21-26-38.png


This reman just got stamped with a dot. I'm pretty sure I've had some with two arrows. Both on top. Whether I have photos I don't know.
upload_2020-5-24_21-29-58.png
 
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The reluctor gets rotated, not flipped over.
You can see why here:
upload_2020-5-24_21-33-20.png
 
Points distributor. Converted.
'72 360, Dodge Truck?

FWIW
'71 Plymouth FSM only has 2 bbl 360 listings - and they have long advances, 14-16*. With initial timings 2.5* BTC. It has a fast and somewhat long initial advance so off-idle the timing will be where it should be for power and economy.
 
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Mattax said:
Points distributor. Converted.
'72 360, Dodge Truck?

FWIW
'71 Plymouth FSM only has 2 bbl 360 listings - and they have long advances, 14-16*. With initial timings 2.5* BTC. It has a fast and somewhat long initial advance so off-idle the timing will be where it should be for power and economy.
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Yes points, converted to electronic. I looked the engine number up a couple years ago. And if memory serves me correct. The engine was installed in vans and trucks. But, I’m sure it was also installed in a couple car models too as the 360 was gaining popularity. How in the hell did you access that additional info ? Mine has an unknown larger cam and it doesn’t like anything less than 20* initial timing.
 
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pearljam724 said:
How in the hell did you access that additional info ?
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360 was introduced as a truck engine. That's in the Mopar Performance manual and the Taylor smallblock rebuilding book which are both pretty reliable. But thanks to Barry, we can see for ourselves what was available for each of those years. Check out the dealership data books here
The 1970 Hamtramck Registry Library Page (1970 - 1974)

As far as the distributor advance and initial timing, those specs are in the back of the electrical section. I have paper copies for 67 and 68, and digital copies of some others that I just need a few pages from as reference. Many of these are available as free downloads from mymopar.com
Timing tape, tachometer and timing light is how I usually figure out what the advance is doing.
Also I've had had access to a distributor machine.

pearljam724 said:
Mine has an unknown larger cam and it doesn’t like anything less than 20* initial timing.
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Like Trailbeast wrote, we can only make general statements.
But if there's a larger cam, then compression and temperature of the fuel/air inside the chamber at idle is going to be poor. So more timing is needed for the flame to develop.
But if the mixture is leaner than best power at idle, that's another reason an engine will want more timing. Flame front takes a little longer to grow with lean mixtures.

So if we compare the non-emmision 273 Hi-Po 4 bbl to the 360 2bbl with emmissions
upload_2020-5-25_9-28-1.png

Initial timing: 0-5* initial timing may have been because the 360 had more effiicent burn at idle than the 4 bbl. But we know from Chrysler's tech booklets that the initial timing was reduced to insure increase the heat in the cylinder walls and exhaust gas. This reduced left over CO and hydrocarbons. They also ran the idle mix leaner. So this combination reduced power at idle, hence the higher idle rpms (750 vs 600 or 650)
Advance to 1600 rpm: This is long and quick to get timing up to where it ought to be for the 360 to have max power.
Advance above 1600 rpm: The engine is in the range where combustion speed is increasing with rpm
Advance above 2400 rpm: The 360 2bbl engine, probably due to the cam, is less efficent at WOT than the 273. So it need more lead time for the burn.
 
My suggestion for your engine. Because the 360 had an early smog curve, the first thing to do is fix reduce the iniital part of the advance curve.
What you did will be OK for a drag race only use. But shorten the total advance by using the 11 plate. That with the two primary springs you now have, should get it into the ballpark. With about 20 degrees of crank advance, work toward getting the initial closer to 15* BTC at a lower rpm and experiment with making the idle mixture richer as you do this.

Lets say the advance curve in your distributor looked like this.
upload_2020-5-25_10-13-22.png


Putting a second spring on it changed the curve to something like this.
upload_2020-5-25_10-15-47.png


But your engine doesn't want an initial timing of 2.5*
I don't know what rpm you measured 20* at.
For sake of discussion, lets say it was 1000 rpm.
upload_2020-5-25_10-21-2.png


This is why the overall advance needs to be reduced from 30 crank degrees. Even if you end up getting the initial timing down to 15* at 800 rpm, 30 in the mechanical advance is too much.

Also when you have the governers out, measure the distances between the inside stops of the slots. Knowing if they are the same or different makes it easier to set up the distributor to do what you want.

upload_2020-5-25_9-54-24.png
 
Mattax said:
My suggestion for your engine. Because the 360 had an early smog curve, the first thing to do is fix reduce the iniital part of the advance curve.
What you did will be OK for a drag race only use. But shorten the total advance by using the 11 plate. That with the two primary springs you now have, should get it into the ballpark. With about 20 degrees of crank advance, work toward getting the initial closer to 15* BTC at a lower rpm and experiment with making the idle mixture richer as you do this.

Lets say the advance curve in your distributor looked like this.
View attachment 1715534795

Putting a second spring on it changed the curve to something like this.
View attachment 1715534796

But your engine doesn't want an initial timing of 2.5*
I don't know what rpm you measured 20* at.
For sake of discussion, lets say it was 1000 rpm.
View attachment 1715534797

This is why the overall advance needs to be reduced from 30 crank degrees. Even if you end up getting the initial timing down to 15* at 800 rpm, 30 in the mechanical advance is too much.

Also when you have the governers out, measure the distances between the inside stops of the slots. Knowing if they are the same or different makes it easier to set up the distributor to do what you want.

View attachment 1715534791
Click to expand...
Without measuring. I put them up to one another bottom to bottom and they look exactly the same in reference to distance. I reinstalled the distributor with two identical lighter springs. I ‘ll know if I like it or not in a few days. If it doesn’t run right. I’m not going to piss with it anymore and swap the bigger spring back in.
 
The point cam lobes are designed to operate points, not a Hall trigger. Hall targets should have a sharp edge trigger, and be made from soft low carbon steel. Trigger target should have abrupt change, not a ramp.

Yeah, engine may run, but timing may be irregular by a few degrees, for every trigger. Most won't notice. A logic analyzer can capture triggers, for checking timming errors. Timing settings will likely need to be retarded to accommodate timing irregularities.
 
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