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Discussion Starter · #21 ·
I just vacuum tested both units. The 14,000 mile one was bad! The adjustable one works perfectly.
 

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Discussion Starter · #22 ·
do you test these by sucking on the vacuum port?
Not me personally....:lmao:

Used a vacuum pump, if it 'holds' without bleeding down, and moves the actuator arm, it's good. Gotta test both sides of the vacuum cannister though. On the other unit I had on the bench it held on one side, but wouldn't pull ANY vacuum on the other side.
 

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Hmmm . . .

I always plugged the vacuum retard port on the distributor, except when my GT required SMOG inspection. Plug the port with a vacuum cap, and you will be OK.
. . . :confused: . . .



. . . plugging the distributor vacuum canister retard port
effectively does nothing as you would remove the vacuum line ('manifold vacuum' source) to do it, no?! Better to plug the vacuum source line so there's no manifold leak, right Lindsay?
 

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Opeler
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Where do the hoses go?

But, what do you look for to plug or cap? :confused:
The attached pictures should help. :thinking:

Message - Opel Photo Gallery
Vacuum Leaks - Opel Photo Gallery

1973 FSM, Ignition System, 1C-19:
The ignition distributor has a double acting double
diaphragm vacuum unit. The advance
unit is supplied with “ported” vacuum. That
is, vacuum is supplied from a port in the primary
barrel of the carburetor located just above the closed
throttle valve. This port supplies no vacuum during
idling nor during closed throttle deceleration, but
supplies full intake manifold vacuum at all speeds
where the throttle valve is opened enough to uncover
the port.

The retard unit is supplied with intake manifold
vacuum at all times by means of a line connected
directly to the intake manifold. During idling and
deceleration, when there is no vacuum to the advance
unit, the retard unit will cause the timing to be
retarded 5 degrees. However, during part throttle
operation when there is vacuum to the advance unit,
the advance unit will overpower the retard unit so
that the retard unit has no effect on timing.
The purpose of the retard unit is to reduce hydrocarbon
and carbon monoxide emissions during idling
and deceleration, where they are especially bad.
 

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Opeler
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http://www.opelgt.com/forums/1b-ignition-system/29812-2-4-cih-distributor-setup-help.html#post276382

I think that 1971-later distributors are easier to modify. They have 28-32 degrees of total mechanical timing. I usually delete the vacuum advance mechanism and lock the breaker plate. Then make the mechanical advance adjustable. 20 degrees of advance would work well for a 2.4. Set the timing at idle at 10 degrees, and you'll have 30 degrees total. I also use two of the 'light' tension springs for the mechanical advance.

Welded breaker plate:


Vacuum advance deleted:


Adjustable mechanical advance. Note the 4 mm set-screw which restricts how far the weights extend.
RallyBob's suggestion for 2.4 distributor setup. Weld breaker plate (or epoxy?), delete vacuum advance, and restrict distributor mechanical advance with a set-screw.
Modification will enable 1971 to 1974 1.9L distributors to be used on the 2.2L or 2.4L.
 

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Discussion Starter · #26 ·
Awesome post.

How do you know how much advance you restricted with set screw?

Only when its running and do timing test? And adjust set screw +/-?
If you know the year of the distributor, you can look up the factory advance. The '71-'74's all had 28-32 degrees of mechanical advance (varies due to manufacturing tolerances). Averages 30 degrees though.

The travel of the weights on Gordy's distributor was .400" in stock form. If I wanted to reduce the total timing by 10 degrees (from 30 degrees), I had to reduce the travel of the weights by 33%, or by about .132". I simply adjusted the set screws so that the total advance weight travel was about .268".

Final testing/verification can be done on a distributor machine, or in a running car.
 

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Discussion Starter · #27 ·
What is the timing for a 2.2 motor? There seems to be confusion as to what is needed on the larger motors...various threads I've read have it anywhere from 28-35* total, and from that it provides a lot of room for error on the distributor side. I am trying to learn and figure this stuff out with more clarity, but to be honest, I don't feel that I'm capable of making the changes to a distributor. However, depending on initial and total advance numbers, specifically to the 2.2, I could better figure out what distributor would pair well with a 2.2. I feel lost and am not sure what is the beat way to correctly time the motor. Especially since timing marks/flywheel ball don't seem to be present or equate to anything, as Keith attested to when he worked in my car last fall.
There's no hard and fast rule because of variations from car to car. Got a stock 2.2 with EFI? Set it to factory specs with a factory 2.2 dizzy. Done.

But for example, my friend Gregg's street 2.2 made its best power (on a dyno) with 36 degrees of timing total, and 20 degrees at idle. But it had 10.8:1 compression, a race ported 2.0 head, big cam, 45 DCOE's, 2.5" exhaust, etc., and was dynoed on 93 octane pump gas on the east coast.

MarkandSon's (Jeff's) Opel GT with a high compression 2.2 would only tolerate 28 degrees total timing on the dyno due to detonation. This has a Megasquirt ECU, distributorless ignition, and a cut-down 3.0 intake manifold and a big valve 2.2 head. I believe he is at about 10.5:1 compression, even though he has the same pistons as the above engine. The larger 2.2 chamber reduced the compression a bit.

Roger Wilson's 2.2 with 2.0 head/big cam/38 DGAS only tolerates 32-33 degrees thanks to 91 octane California pump gas, also at about 10.5:1 compression.

My friend Dave's old race engine (2.2 crank in 1.9 block with 1.6 head) made best power at 36 degrees on 104 octane race fuel. At 38 degrees of timing it lost 12 hp. At 33 degrees it also lost 12 hp. Narrow window!! It had 11.21:1 compression, but with flat-top pistons and a small chamber head instead of domed pistons like the other engines above. They are more tolerant of timing due to better flame travel.

If you make the distributor adjustable, you can make it whatever you want. If you drop in a '75 dizzy...it is what it is.
 

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Bikini Inspector
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Great thread to help us mere mortals understand....

here is the LINK and here is an excerpt from down under... GT JIM also see post 62!! vacuum measurement is the determining factor

The "Total" advance you are quoting from the FSM is made up of mechanical advance of around 30 to 36 degrees (crankshaft) and vacuum advance of 14 to 20 degrees - depends on the actual specs of the distributor you have as there are variations both between years and between actual distributors.

The only conditions that the motor will "see" 50 degrees of total advance are at above about 4,000 rpm on the over-run when the throttle plate is closed. In this condition the manifold vacuum is high enough to pull vacuum advance and the motor is reving high enough for the full mechanical advance to be all in. The motor tolerates this large advance because at high vacuum the fuel/air charge going into the cylinders is quite rarified (low pressure) even after compression and requires LOTS of advance to burn at all.

Under acceleration or even cruising the throttle plates are partially open and manifold vacuum is not as much and cylinder pressures are higher - ignition advance depends almost entirely upon mechanical advance - about 34 to 36 degrees total advance. The is NO vacuum advance added to the mechanical advance under these circumstances and cylinder pressures are much higher at the end of the compression stroke just before ignition.

Detonation usually only occurs at wide open throttle with too much mechanical advance - which is entirely influenced by initial (set) advance when the distributor is installed and statically 'timed'. Changing initial advance changes the amount of full advance by the same amount.

For instance - standard carb. motors are set at zero degrees initial advance and have about 35 degrees in the mechanical advance. The Fuel Injection distributor is set at 10 degrees initial advance and has only 25 degrees in the mechanical advance for a total of 35 degrees advance.This is ignoring any vacuum advance/retard as it is not relevant at wide open throttle as there is little or no vacuum.

The important measurement is total advance at wide open throttle at 3,500 to 4,000 rpm - this should be in the range of 34 to 36 degrees. If detonation occurs at these settings and under these conditions then you are not running high enough octane fuel or too much compression for the fuel being used. The temporary fix is to reduce initial advance ... and thus total mechanical advance - but his also affects engine performance.

The correct fix is to recurve the distributor to allow initial advance and reduce total advance by limiting the mechanical advance in the distributor - as the 1975 distributor has had done at the factory - or, by ones self, as outlined in other threads on this site.

NONE of the factory distributors (except the 1975 FI unit) are suitable for hi-performance motors without modification to the mechnical advance curve.

HTH
 

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Opel Key Master
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HERE ARE SOME MORE GAS CAPS FOR U

a vacuum advance will affect timing until around 2500-3000 rpm's then it is mech only.
This isn't true, disconnect your vacuum advance and run your engine at 3000 RPMs and see what your advance is, then hook up the vacuum and it will increase. Now vacuum advance usually doesn't activate until the carb sees about 950-1000rpms....but your statement makes it sound like vacuum advance is not advancing after a certain rpm. The vacuum advance doesn't shut off after 3000 RPMs that I am aware of. Also around 3200 RPMs or less you should have full advance, the springs will control this as a lighter spring with open the weights up earlier. Now I understand that vacuum decreases when at wot but it doesn't take much vacuum to keep that pot open...it's hard for me to believe that it isn't pulling vacuum advance cruising at 3000 rpms
 

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Discussion Starter · #30 ·
Hi Bob, sounds like a good set up especially with a side draft Weber (having no vacuum advance port) it would be interesting to bang it on a dyno after a run while the engine is hot and see how much advance works best. Then set it 2 deg less for safety. Do you know what RPM it hits max advance? Like I said sounds like a good setup and Gordon is lucky to have it.
Hmmm, I can't recall exactly, but usually by 3600-3800 rpms it's all in.

This can be altered by changing spring rates, or by changing the mass of the counterweights.

Lighter spring/heavier weights = earlier advance, while stiffer springs/lighter weights = later advance.

How much mechanical advance (quantity in degrees) is controlled by those adjustable screws I added, but it doesn't affect how fast it comes in.

 

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Mechanical advance

I would do whatever needs to be done to get back to "starting" setting, "idle" setting and "total" setting.[/QUOTE]

Thanks for the reply. Yes I do understand the ratio between the crankshaft and the distributor 2 to 1. I think if I understand you correctly ported vacuum plugged offidle setting @850 RPM's book says 0° TDC and total @35° @ let's say 4000 RPM's (after its all in on the mechanical advance). The starting setting is something new to me and I don't know how to measure it. Do you mean cranking the engine to see where my timing is? Yes you are correct, my GT was a PIA to start warm after sitting for an hour or so and sometimes cold but I'm pretty sure I had my idle setting at between 30-40° advanced with a locked up mechanical advance. My line of thinking now is how much initial advance at idle setting can I get away with without having those starting issues? I'm thinking 10-15° might be harmless. I liked Travis's way of setting up because the mechanical advance can be backed off if needed I attached the pic . I've also seen Gordos Rally Bob modified mechanical advance. Have you successfully tried giving yours a little advancement at idle, if so how many degrees would you recommend limiting your advancement to at idle? That's what dictates my total advance setting. Isn't 36° or close to where my total should be for maximum power? I guess I'm buying into what the guy said about advancement at idle = cooler running combustion also. I hope that makes it easier to understand my thaught process? Agree or disagree I read a lot of your posts and would value your opinion.
 

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Discussion Starter · #32 ·
FYI, anything above 36 degrees tends to lose power. I’ve seen a 12 HP loss going from 36 to 39 degrees on a dyno.

45 degrees is wayyyy too much.

You don’t need a 1975 dizzy, any 1971-1974 can be modded to be adjustable.
 

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Can Opeler
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I’m going to make a couple videos about the Opel distributors to help some people out. My first video is just a clean up of a 1975 distributor, but there is some good stuff in it for those who have never seen the guts of their distributor and it should help a little with tear down, but my later videos will be much better.

My next video will be more technical. I will be fully rebuilding a 73 distributor to replace the worn bushing. It might be a bit before I get around to it.

https://youtu.be/CjvfETPLv_E
 

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Spring replacement options for mechanical advance

Since the days of looking through junkyards for old VW distributors and mechanical advance springs are gone. I wanted to post this link I found along with a little helpful information. They can be used to modify the distributor curve using the existing weights in the distributor. I’m not trying to re invent the wheel or anything because what we already have is pretty good but with the mods we are putting in and today’s fuel this looks appealing to me there’s a $40 minimum order I believe. I’m going to order the ones checked off that are pretty close to stock sizes and should work pretty well. The thickness, diameter, length etc. of the springs are very close. There are two types of material stainless (not as stiff) & music wire (what most distributor’s use). More selections and better details on the link below just enter the part number off my list below.


http://www.centuryspring.com/extension/extension-springs.html?limit=36&p=23

Stock GT springs
.016”Th.x.173”dia.x .217w x .531”L end to end of loops (small spring)
.027”Th.x .183”dia.x .282w x .772”L end to end of loops (larger spring)

Century Spring pt#’s

Pt#———-Dia.—-L.—-Th.
ZZ1-35 .156, .630, .020, (5.1 lbs) $1.46✔
493 .156, .540, .018, (3.3 lbs) $1.91✔
N-307 .172, .470, .020, (5.8 lbs) $1.56
417 .172, .5, .023, (14 lbs) $1.79
ZZ4-51 .172, .630, .027 (16 lbs.) $2.05✔
ZZ2-31 .172, .690, .25, (9.6 lbs) $3.23✔
456 .172, .630, .020, (3.6 lbs) $1.46✔
80172 .180, .630, .024 (9.2 lbs) $7.50✔
80185S .180, .630, .026, (12 lbs) $8.44
80132. .180, .630, .018, (2.1 lbs) $7.37
80160 .180, .630, .022, (5.9 lbs) $7.37✔
8021S .180, .630, .030, (30 lbs) $8.28
80185 .180, .630, .026, (14 lbs) $7.37
80132 .180, .630, .018, (2.1 lbs) $7.37
80146 .180, .630, .020, (3.6 lbs) $7.37
80210 .180, .630, .031, (35 lbs) $7.37
80155. .180, .630, .020, (.66 lbs) $7.51
6075 .188, .630, .025, (8.5 lbs) $3.41✔
5420 .188, .630, .020, (2.4 lbs) $1.46✔
M-43 .188, .50, .019, (4.1 lbs) $1.43✔✔
S-515 .188, .50, .015 (.74 lbs) $3.49
5513 .188, .690, .024 (6.8 lbs) $1.49✔✔
ZZ1-7 .188, .690, .020 (3 lbs) $3.20✔
J-45 .188, .50, .020, (5.4 lbs) $2.16✔
5417 .188, .560, .017, (1.5 lbs) $1.50✔
M-9. .188, .630, .020, (2.5 lbs) $1.79✔✔
A-46 .188, .530, .014 (.780 lbs) $1.46
5408 .188, .590, .020, (3.6 lbs) $1.55✔✔
N-92 .188, .560, .023 (6.5 lbs) $3.03✔✔

Here’s where I got the idea. It’s a very interesting read.

http://www.sparkingplugs.com/resources/BSmith_356Registry_Stroke+Spark+Springs+Smith+38-2.pdf
 

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I am about to assemble my upgraded 1.9 CIH engine. It has 0.040"-over forged flat top pistons, stock (for now) valves & springs, a Combo Isky OR66H (Hydraulic lifter) 0.420 lift 268 degree duration cam, the cam gear slotted and drilled for a Comp Cams SBC off-set bushing (initial setting to be 4 degrees advance for improved low end torque). Fuel is provided by a 38DGAS and ported & tented intake manifold, and exits via a Sprint exhaust manifold thru a 2" exhaust system (stock muffler & resonator, again for now). It has a lightened flywheel (19.6 lbs down from 22.6 lbs) and the stock 8" clutch driving a Getrag 240 5-speed. The engine (pistons/crank/rods/pulley) and clutch/flywheel rotating assembly parts are fully weight-matched and dynamically balanced to 0.1 gram.

My goals are driveability and fun, spirited cruising, not racing. My horsepower goal is a tidy 100, and a similar torque output at a useable rpm.

It is time to decide on a distributor, and I have collected several over the years. I am inclined to modify whichever distributor I chose, and perhaps even a couple, to try different versions. To that end, I am learning by reading and accumulating posts and photos on this site relating to CIH distributor options and modifications. This thread is intended to provide a one-stop place to read about distributor options, especially as it relates to initial and advance.

I will be leaving this thread closed until I can copy a number of related posts from other threads here, but I have started by copying over some posts that are part of RallyBob's thread "CIH Turbo EFI by RallyBob". That in itself makes some terrific reading, but it can be challenging to pull out six distributor-related posts out of 440 (four hundred forty!!!) posts to date in that thread.

When I open this thread, please refrain from chit chat and casual comments, as I hope to keep this thread on-topic and relevant. If you have real-world experience and learnings, we are very interested in what you can share.

Please stand by....
 

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I'll start by documenting the modification of a '75 distributor, with advance stops on the mechanical advance, and the vacuum plate locked. Over the years, I have collected a number of distributors, including a NOS '75 model, and a NOS dual vacuum pot (~1972) distributor. The first photo is my current inventory of Opel CIH distributors.

Based on what I have read, mostly written by RallyBob (Bob Legere) and copied into the beginning of this thread, the goal is to make the mechanical advance limit adjustable, aiming for ~20 degrees of maximum advance at approximately 3000 rpm, and ensuring that maximum advance is 34 to 36 degrees BTDC. That compares to the factory limit (created by tabs on the edge of the '75 mechanical advance plate) of approximately 25 degrees at 3400 rpm. Earlier versions have a quite different mechanical advance design, so these next few posts will be only related to the '75 distributor. I am also building a modified distributor for another Calgary Opel'er, Sterling Rempel, which will be based on a 1971 distributor. I will document that modification in a later set of posts.

The next three photos show a '75 distributor. They look similar to the earlier versions, but can be identified by the serial number ending in 170 140, having ONLY a vacuum retard pot which pulls the breaker plate CLOCKWISE, and the points are outboard in the distributor body, vs inboard for all the earlier versions. The 4th photo shows a 1971 distributor (with the combined vacuum advance/retard pot) on the right, the '75 distributor on the left.

The 5th photo shows indents on the body of the '75 distributor, which is different than the earlier versions, and those indents "hold" the breaker plate in the body. Earlier versions only rely on the cap spring bolts. The '75 distributor requires that the cap spring bolts be removed, and THEN the breaker plate rotated clockwise to release it from the three body indents. I found that inserting a flat-bladed screwdriver into one of the triangular gaps in the breaker plate, and then tapping it clockwise until the indents cleared worked. The breaker plate can then be removed (once the remaining things, such as the points and condenser and vacuum pot are also removed). That reveals the mechanical (aka centrifugal) advance mechanism, shown in the 7th photo,

To remove the distributor shaft, the spring clip, washer and drive gear must removed. I have generally been able to drive the retaining pit out, but these last two distributors required that I drill a 1/8" hole through the pin and then drive the pin out (photo #8). A new pin can be sourced at most hardware stores, using a 5/32" x 5/8" hardened roll pin. The OEM pin measures at 4 mm x 16 mm (0.157" x 0.630"), and the roll pin kit I have has 5/32" pins that are slightly larger when uncompressed (of course) than 5/32" (0.156"), closer to 0.167", and they seem to work fine.

Removing the shaft and mechanical advance mechanism, I took that opportunity to polish the housing. Oooh, shiny!
 

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Ok, the guts are out. On the other distributors, I popped the mech advance springs off, and the rotor shaft part off the main shaft as per Bob's direction. A quick tap with a 3/16" drift (after removing the felt pad) while hovering the shaft over the bench so it didn't all go flying, and the spring clip and washer below popped off, allowing the rotor shaft to be removed. On two of my distributors, the oil inside the rotor shaft had turned to varnish, seizing the shafts together, and there was NO MECHANICAL ADVANCE!!!

The next step is to modify the mechanical advance plate. Following Bob's directions, I drilled and tapped a hole in each of the limit tabs. I happened to have purchased a bag of Chinese M4x 6 mm stainless grub screws. A 1/8" or preferably 5/32" grub (aka "set") screw would work fine.

The set screws limit the outward movement of the mechanical advance weights, thereby limiting the advance. Both sides have to be modified. Following Bob's suggestions above, I adjusted the screws (once both tabs were bent to an equal distance, which they were NOT initially!) to reduce the weight travel by 0.087". That dimension is a bit unique to each distributor. In this case, I wanted to reduce the factory advance limit from 25 degrees to 20 degrees, or about one fifth. The initial travel was 0.435", so the set screw protrudes one fifth of the initial distance. That will have to be verified with my degree-adjustable timing light when the engine is run through the rpm range. Fortunately the '75 distributor has an additional port in the body, that happens to line up with the limit tab. I suspect that is by design, allowing the tabs to be bent to adjust the mechanical advance limit without disassembling the distributor. That can be done instead of the set screws, but is pretty coarse in setting the limit. I think that the set screws can be adjusted in the car, although I used a wicking grade of "firm" Lok-Tite to ensure the set screws don't back out, so that will have to be re-applied.
 

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The next step of locking the vacuum advance plate is somewhat optional, in my mind. I like the idea of vacuum advance, increasing ignition timing advance at initial throttle tip-in. But I am using a fairly high lift cam, and I have been warned that the intake vacuum will be reduced and inconsistent, thereby making the vacuum advance unreliable.

And there is no way that I could figure out to simultaneously limit BOTH mechanical and vacuum advance. They are separate systems, so to limit the total advance to 36 degrees BTDC, eliminating vacuum advance is logical.

One thing I did contemplate was leaving the vacuum RETARD functional. On the '75 distributor, that retards the ignition by 4 degrees when the throttle is closed. Merely opening the throttle eliminates the retard, thereby advancing the spark 4 degrees. So if the static timing was set to 14 degrees, that would make it 10 degrees WITH the retard functioning at idle, advancing to 14 degrees again on throttle tip-in. Seems elegant, but there must be some other issue I am not contemplating

In the '75 distributor, the breaker plate (which was removed to modify the mechanical advance) is very easily locked. There are already a pair of holes that line up almost perfectly at the mid-point, so I just had to ream them out a bit and pop rivet the plates together with 1/8" rivets. I have read about folks welding the plates, but I cannot see the need to do that. Pop rivets are robust, easy to install, and easy to remove if vacuum advance is desired in the future.

The earlier breaker plates do NOT have a pair of convenient holes, so it had to be drilled and I will show that in the later set of posts.
 

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I skipped over a pretty important consideration, and that is what springs to use on the mechanical advance. You could simply leave them as-is, assuming that the "advance curve" from the factory is acceptable. One spring is quite thick, while the other has an extended loop but is also thick and has a high spring rate, so that it doesn't resist until some middle rpm is reached, and then presumably the rate of ignition advance vs rpm decreases). But Bob suggests removing both the '75 springs and replacing them with a pair of the shorter, lighter springs from an earlier distributor. The earlier springs have thinner wire and a lower spring rate, and one also has the extended loop, but as the posts are closer, both are shorter. But not short enough to apply closing pressure at an idle on the '75 mechanical advance mechanism.

Here is a photo to compare the springs from a '71 and '75 distributor, and several other springs that I made from some I had. The '75 spring posts are a bit further apart than the earlier mechanism, so the early soft short spring maintains some additional force to hold the advance constant at low rpm. I elected to install one short spring and one "made" spring of near-equivalent spring rate. I suspect that the science of mechanical advance spring rates are quite involved, and I won't pretend to know how to break into that club.
 

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I found an additional source of distributor specifications for the various years that someone put together years ago. Sorry if I don't provide credit, but i simply don't recall where it came from. I modified it to reflect engine rpm vs timing (vs the original distributor rpm vs distributor timing) and also added some specs from the '71 and '75 FSM's. I trust that this is useful.

OK, it might be a few days before I get to posting the details on modifying an earlier distributor, so I will open this thread for input. Please refrain from chit chat and casual comments, as I hope to keep this thread on-topic and relevant. If you have real-world experience and learnings, we are very interested in what you can share.
 

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