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Discussion Starter #1 (Edited by Moderator)
MODERATOR'S NOTE: I have compiled this thread as a "best of" and most relevant set of posts relating to identifying, diagnosing, and modifying the Bosch distributors on the Opel CIH engines. 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.


Here is a listing of US-spec distributor advance limits for 1.9 litre engines. One item worth noting is that automatic-equipped versions of these model year Opels had different advance rates (the advance occurred sooner), which was accomplished by using lighter tension springs on the mechanical advance. This was to help improve acceleration. Part numbers for the distributors for automatic-equipped cars were different than the same-year manual-equipped cars, but they were otherwise identical in operation. Except for 1975 Opels, all US-spec 1.9's had the static (idle) timing set to 0 degrees BTDC (before top dead center). Note that the engines had less and less total timing as the years progressed, in the interest of reducing exhaust emissions. Opel 1.9 litre engines tend to make the most power with a total timing figure of between 34-36 degrees.

1968 - 32-36.5 mechanical advance
19.5-22.5 vacuum advance
51.5-59 degrees total

1969 - 32-36 mechanical advance
11.5-14.5 vacuum
43.5-50.5 degrees total

1970 - 32-36 mechanical advance
11.5-14.5 vacuum
43.5-50.5 degrees total

1971 - 28-32 mechanical advance
7-10 vacuum
35-42 degrees total

1972 - 28-32 mechanical advance
7-10 vacuum
35-42 degrees total

1973 - 28-32 mechanical advance
1-5 vacuum
29-37 degrees total

1974 - 28-32 mechanical advance
1-3 vacuum
29-35 degrees total

1975 - 25 mechanical advance
5 degrees static timing
no vacuum advance unit
30 degrees total
 
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Discussion Starter #2
As I need to order some components to create my EFI compatible fuel tank, I decided to concentrate on the distributor for the engine instead today.

After the tear-down, all the parts were cleaned in preparation for modification to the advance mechanism. Here they are, laid out.
 

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One of the more critical aspects after removing the vacuum advance, is making sure the upper breaker plate doesn't float around and alter the timing randomly. To ensure full accuracy, it should be centered in the 'neutral' position rather than advanced or retarded, at least more or less....
 

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Discussion Starter #4
Once the breaker plate was centered, I riveted the two plates together to keep them from moving.
 

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This is the position of a fully extended advance weight. For this year distributor, mechanical advance is listed as 28-32 degrees. My intention is to set the baseline timing at 10 degrees, and let it advance to a maximum of 25 degrees. So I need 15 degrees of maximum advance for this to work, which is roughly half of what the stock advance happens to be.
 

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Here's the same advance weight in its' fully retracted position. Note the gap between the two black marks....it's about .400" wide. I'm targeting reducing this gap to .200" to cut my advance in half.
 

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This is my solution for reducing the amount of advance this distributors sees. I drilled and tapped the advance weight stops, and used a couple of 4mm allen screws as limiters. The screws can't be too long or they will hit the inside of the distributor housing BTW....

I used high strength Loctite to secure the set screws. Both sides are needed, and they must be adjusted equally.
 

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Remove cam assy from center shaft?

RallyBob said:
As I need to order some components to create my EFI compatible fuel tank, I decided to concentrate on the distributor for the engine instead today.

After the tear-down, all the parts were cleaned in preparation for modification to the advance mechanism. Here they are, laid out.
So Bob, what is the trick to removing that pesky little clip to separate the distributor cam assembly from the center shaft???
:confused:
 

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Discussion Starter #9
No trick Otto, takes 5 seconds. Clamp the cam portion in a soft-jawed vise, remove the felt plug from the center of the assembly, take a suitable drift (I used a 3/16" drift), tap once with a hammer, the main shaft falls right out.....
Best done with a set of helping hands so the parts don't fall to the floor. I usually end up doing it myself, but I taped the parts loosely together so they don't fall far.

Now replacing the clip is another story. Sometimes it takes me 10 seconds to put it back on, other times 10 minutes. Thankfully this time it only took me three attempts. I just drop the clip in place over the end of the main shaft, then using a pair of tiny needle nose plier push downwards. That's it.
 

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Discussion Starter #10
Made a sheet metal cover for the open holes in the distributor housing.
 

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Discussion Starter #11
GoinManta said:
Hmm I wonder is these numbers correlate with the nuber on the arm of the vacuum can? The numbers were different on the two I have. I am curious which ones I have.

Bob, you have any preference?
The year of the distributor is on the distributor body itself.

My preference? I like the '71-'74 these days...I used to like the older ones, but found a better way to modify the late ones. The vacuum cannister doesn't make a difference to me however, as I never use vacuum advance anyway due to my typical cam choices.....

The '71-'74 distributors are the same except for the vacuum advance. Automatic versions have slightly lighter springs to aid initial acceleration (it doesn't work!).

Bob
 

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Yep, that's me!


Anyway, I was wondering what thoughts experienced people might have with disconnecting the vacuum retard from the distributor. I'm running the 2.0E with a stock 74 distributor (stock except for the Pertronix).
I have some 'oddness' with my idle that seems to go away with the retard disconnected. I have eliminated every vacuum leak I have found and the vacuum advance/retard diaphragms hold vacuum just fine.

Are there any ill effects to running without the retard?
 

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Vacuum retard . . .

Yep, that's me!

Anyway, I was wondering what thoughts experienced people might have with disconnecting the vacuum retard from the distributor. I'm running the 2.0E with a stock 74 distributor (stock except for the Pertronix).
I have some 'oddness' with my idle that seems to go away with the retard disconnected. I have eliminated every vacuum leak I have found and the vacuum advance/retard diaphragms hold vacuum just fine.

Are there any ill effects to running without the retard?
In a word, NONE! The vacuum retard is only active at idle and is strictly an anti-pollution device, so you're perfectly fine leaving it disconnected. I would disconnect and just tune your disti again without it . . . probably no adjustment required, since you're supposed to set the disti initial timing with no vacuum hoses attached in the first place!
 

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As Otto states, the vacuum pod activates at High mainifold vacuum such as idle. Also it retards the timing any time the throttle is closed such as when lifting off the gas beteen gear changes or when you depress the clutch when coming to a stop. Therefore it does help the idle settle back down to the idle rpm a little quicker. If, after disconnecting it, you find a small change with the engine returning to idle as quickly as before, then you'll know what caused it.

BTW, I've had the diaphram in the vacuum pod leak and cause the same roughness you describe...

Advancing initial timing to 5 degrees should have the same effect as unhooking the vacuum pod.
 

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Actually, . . .

Jeff
Forgive the dirty caps. I had to dig them out from storage.
As been mentioned there's two different styles of hold downs. Maybe this picture will help.

. . . you're not showing dizzy cap 'hold-downs', you're showing the two types of cap's 'location/orientation' methods . . . matched to their dizzies below . . .

 

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Stock Bosch Distributor Numbers

Bosch distributor housing numbers

1.1
1966-67.................150 003
1968......................150 006
1969(to6/69)...........167 004
1969(after6/69).......167 023
1970......................167 009
1971......................167 004

1.5
1968......................167 001

1.9
1968.............................167 001
1969(mtrans to6/69)........167 005
1969(atrans to6/69).........167 006
1969(all after 6/69)..........167 024
1970-71.........................167 007
1972 mtrans....................176 012
1972 atrans.....................176 011
1973..............................176 012
1974..............................176 012
1975..............................170 140
 

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Discussion Starter #18
Anyone have a source or replacement part numbers/manufacturers for new vacuum advance pots for the 1.9's?
What year?

They're all different vacuum values (early has more advance, later has less).

I probably have 40 or 50 of them I've removed from distributors that I've prepped for performance use. I just pulled one from a '71 yesterday. Only 14,000 original miles on it.

Pay for shipping and I'll send one to you.

PS, this should be posted in the electrical forum, under this sub-forum 1B - Ignition System
For future use, and to keep the moderators happy...
 

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Discussion Starter #19
RallyBob, that would be great, thanks. I have a 1970 GT. I guess I'll just use that disty for the rebuild. I also have one out of a 1973 I was going to rebuild and install. Is there a difference between the 70 and 73? How do you want payment made? Paypal? give me your Paypal email info or your snail mail address and I'll get $$$ out to you next week.
1970 was the changeover year for distributors, and 1971 was theoretically the start of the newer style. However this particular advance unit came off a '71 distributor which in fact uses the older style advance mechanism.

So I'm not sure what you have. Here's some pics of the vacuum cannister for the advance mechanism:
 

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Discussion Starter #20
I just found another advance unit on my bench, and it has the adjustable vacuum advance screw on it. There's an eccentric cam which allows you to fine-tune the vacuum advance limits.
 
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