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Opel Guy
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Solex vacuum lines

I had the Solex and manifolds off my 70 GT to replace the gasket. I didn't get back into it for a few months due to other projects. Now I have someone interested in buying it. It runs but VERY rich. Does anyone have a picture or schematic showing where the vacuum lines run? The one I can't find a place for is an 1/8" molded clear line with short rubber hoses on the ends. I have the vacuum advance hooked up. There is also a 1/4" nipple on the bottom that needs a hose. All my manuals don't show vacuum lines. The car used to run fine! I know thw Solex is junk. My 72 GT has a Weber on it that works fine. I just need to get it running well enough to sell. Any help?

Super Moderator
6,533 Posts
Slo-Ex Vacuum Connections


After re-reading the question you e-mailed me, I think you were asking where the 1/8 inch plastic line connects to. I believe you are referring to the distributor vacuum retard line. This connects to a small metal tube on the outboard side of the intake manifold, on the big tee that is the brake booster connection. In jpiper's picture, this is labeled "Distributor line goes here, mine is plugged". This connection isn't very necessary, as it just retards ignition timing at idle, and is the one "pollution controls" connection that can be safely eliminated. Just plug the tube end at the manifold to keep it from leaking.

The other distributor vacuum connection (the "advance") is shown in picture immediately above that, and is the yellowish plastic line connected to the carb body with the black rubber tube.

Make sure you have the valve cover PCV connection made, which is the small hole in the valve cover. On early models, this connects to the outboard side of the intake manifold via the small metal tube just below the tee. It is very difficult to see, but it is labeled in the picture. Later models had this connection on the inboard side of the manifold, just below the carb base.


Super Moderator
6,533 Posts
Vacuum Connections to the Solex and Other Mysteries Solved...


Ah.... Puzzle solved. It some particular order, here are the connections:

The small vacuum line on the booster tee (which is actually on the manifold, BELOW the carb, and hence below the throttle plate) is the "vacuum retard" connection. This goes to the smaller vacuum connection on the distributor. This vacuum retards the ignition timing when the engine is at idle, helping to reduce NOX emissions. But between me, you and the fence post, it does so at the expense of increased fuel consumption at idle. Unless you are getting the car emissions-checked, this is one connection that can be eliminated. Just make sure you plug the tube on the tee, or you will have a vacuum leak.

The connection on the same side but on the carb body, but just above the carb base, is the "vacuum advance" connection. It is ported just ABOVE the throttle plate, so it has no vacuum at idle. But when you "step on the gas", the vacuum below the carb venture causes the timing to advance, which is a "good thing" (in Martha Stewart lingo). This, of course, connects to the bigger connection on the distributor.

You probably have these right, but there are four (4!) more connections.

First, you have the "PCV metered orifice". There is no PCV valve (per se) in an Opel CIH engine, at least of the vintage we are discussing (by the way, what year is yours). Rather, there is a small metered orifice in the manifold that "sucks" a precise amount of crankcase gas into the manifold. On pre-73 manifolds, it is a small tube just below the booster tee. On post-72 engines, it is on the other side (inboard, or valve cover side) of the manifold. It is about 3/16 inch in diameter, but has a very small hole (an "orifice") in it as it enters the manifold. This connects to the small hole in the valve cover, and sucks crankcase gases out of the engine, at least at an idle.

Second, you have the "big PCV" connection. This is the 5/8 inch hose that connects the big hole in the valve cover to the air cleaner assembly. At idle, this allows filtered air to enter the valve cover to replace gases that have been sucked out by the PCV metering orifice. This is equivalent to a "breather". At higher rpm (when more gas is generated, and when there is less manifold vacuum, but more carb body vacuum, downstream of the filter) the excess crankcase gas EXITS through this hose, and is sucked into the carb throat to be burned. Note, there is NOT a PCV valve on this hose!!! Some owners install a PCV valve and disconnect the small PCV hose, which causes the crankcase to pressure up, forcing oil past the seals. This is a "bad thing"!

Third, the carb float is vented back to the charcoal canister. In the picture, this is the front connection, on the inboard side of the carb. When the engine is shut off, excess gas fumes from the bowl that would otherwise be vented to the atmosphere are stored in the canister, to be burned later.

Fourth, the connection at the back of the carb, inboard side, is the connection to the charcoal canister that allows the stored gas fumes, and gas fumes from the tank venting system, to be drawn into the carb body when the engine is running. This is ported to the carb throat, just below the venture, and sucks gases from the canister into the carb to be burned.

The connections between the tank, canister and carb can be seen at
http://groups.yahoo.com/group/class...tion/CIH Emission Hose Routing/evap_lines.jpg

Not a great picture, but it should give you idea. A better view, combined with an article on the issue of tank venting, can be seen at

Now you should be good to go.

Keith Wilford

-----Original Message-----
From: [email protected] [mailto:eek:[email protected]]
Sent: November 3, 2002 5:20 PM
To: kwilford
Subject: RE: THANKS!!!!!

Keith, I was looking this afternoon. There are 2 small
lines, one from a Y at the base of the carb and the
other comes out of the carb further up. Both of these go
to the distributor. At the base of the carb at the Y,
the power brake booster connects. There is a check valve
in that line. I still have 2 1/4" outlets on he side of
the carb near the valve cover that I don't see where
hoses would connect. I don't have any open ports
anywhere. The picture you sent shows those 2 hoses and
the one from the valve cover running in front of the
carb and going down where the booster conn is. This one
has me puzzled. Been working on cars for 35 years and
was a mechanic at a Chrysler dealer for 10. This has me
stumped. I'm going to take apic tomorrow. Thanks for all
your help. Jeff
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