My Solex to Weber Conversion: Pictures and Notes

[agav]

Hi everyone,

As some of you have followed here, I have had quite a few problems with my Solex 4A1 in a 1975 California 280S. Rough idle, stalling, balking, engine dying, and in the end the mixture was too lean due to vacuum leaks and idle mixture screws didn't do a thing anymore.

Anyway, I bit the bullet and embarked on a fun learning experience and wanted to share my journey with you - may it be helpful to someone in the future and I am sure there will be a couple of questions along the way from me.

#1 - The old Solex
As you can see from the pics, the Solex was in pretty warped condition. I did attempt a rebuild, trying dirty tricks like gasket maker, but ultimately it just didn't yield any results. The bottom line is that you never want to over-tighten the screws that bold the Solex onto the intake manifold. Hand-tight is probably just enough. When too tight and exposed to heat, the result over time is what you see. Impossible to hold a vacuum, especially when it gets warm.

[agav]

#2 - The replacement is here

I ordered the Weber Redline kit #248 from a seller on eBay for ~$US500. The kit should in theory come with everything needed for this particular conversion on an M110 engine: Intake manifold adapter plate, throttle linkage, screws, hoses, etc. I read mixed reviews (concerns about restricted airflow) but decided to go with it since it seemed to be the most straight forward for someone like me who never swapped a carb before.

As you can see, the baseplate was a relatively corse aluminum cast. I sanded it down slightly to get rid of the surface imperfections. The photo is before I sanded it. I used a 500 sandpaper on an old glass window and ground it in circular motion. The base plate is angeled slightly on the carb side, so I had to be careful not to round off edges but keep the angled surface.

[agav]

#3 - Carb mounted

Ok - so the carburetor is mounted. Here is the process I followed (and if the pros spot anything I should have done differently, please chime in!

• Cleaned the intake manifold mounting surface with a scraper and soft wire brush. Plugged the intake manifold with two shop towels to make sure no dirt goes down there. Lots of carbon built up in what I assume is an exhaust return within the manifold. You do not need the thick, previously installed bakelite insulator anymore.
• Mounted the aluminum adapter plate / base plate from the kit. Oddly enough, two gaskets and a thin metal plate between those go under the base plate (probably for the right hight). I coated the supplied gaskets with grease to make sure they seal better.
• Proceeded mounting the carb, same procedure here, but just one thick gasket (this one has the insulator that was previously directly on top of the intake manifold). This time, I was definitely careful tightening those screws!

[UTn_boy]

If your area requires this old of a car to pass emissions, it probably won't now that all of the vacuum switchover valves will no longer be operational.  Hooking them up to straight intake vacuum won't work because some are connected to ported vacuum. 

In addition, that little rubber grommet that is between the intake manifold and the cam box....that looks like an upside down top hat....it has a vacuum line going to it that is connected to intake vacuum.  This needs to re reconnected.  If it's not, here is what will happen:

The M-110 engines, especially the carbureted ones, end up having an excessive amount of blow by.  It's just their nature.  This set up allows for a constant suction within the crankcase that is taken into the combustion chambers for burning.  If it's left unhooked,oil will start creeping out of every orifice/seal of the engine possible, and your air filter will swell up like a balloon where the valve cover vent hose hooks to it.  Also, the air filter housing will start puddling up with oil on the inside. 

If the rubber grommet I am speaking of is hard and no  longer soft, replace it.  It's cheap, and will prevent a vacuum leak, too.  Part number 110-997-26-82.  When you go to order this, its description will read as "power steering hose VLRUB".  Ignore that.  It's the right part, I promise. 

[agav]

Hi UTn_boy, always great to get your feedback!

I'll post a couple of more pics with minor progress later today since I am confused about the vacuum setup but to your post:

• Pre 1976 in California - smog exempt. Wouldn't have passed it before either. 
• I'found the little rubber grommet on eBay and just ordered it, was a couple of bucks. Other than the one online (http://www.ebay.com/itm/361469651043) I noticed though that the one on my car has a port that is hooked up to the exhaust system with a line feeding into the EGR valve (there was a metal "T" line branching off into the Solex as well in between before I took the Solex out). I don't recall a separate vacuum port - but also not at home right now to check. See the pic I attached. Maybe I did something weird here?

Thanks!

[ptashek]

Excuse my utter ignorance, but how much work would it be to convert a carbed M110 to a K-Jet?

[UTn_boy]

Don't the fuel injected M-110 engines have different camshafts and distributors?  In addition to finding the fuel injected parts like the intake manifold, cylinder head, breather, and fuel distributor, you'd have to source a wiring harness, too.  It would definitely be a lot of work, but the cost involved would likely be much more than what AGAV is doing at the moment.  Maybe I'm incorrect in some of what I've mentioned, but it's still something I wouldn't want to do, but to answer your question, yes, it is possible. 

Agav, Are you sure about the smog stuff?  In all of your pictures I see things like a purge valve, a float chamber vent valve, vacuum operated fuel return valve, etc.  These goodies were't available/required until sometime in 1975. 

The line going from this little rubber grommet is not supposed to be hooked up to the EGR valve.  This line connects to the back of the carburetor at it's own personal connection, and then T's off over to the purge valve.  There are no other connections allowed at this juncture. 

[agav]

Strange, strange. I wonder why it was assembled that way in the first place with the Solex on place. Tonight, I'll post a photo of what I had set up prior. Or maybe I am just really confused and need the weekend to begin .

Yeah, pretty sure about the smog stuff. "Audrey" is a 1975 (on the title at least, MB told me it she was built in late '74) and definitely exempt here in Cal by the DMV.

[UTn_boy]

Well, who is to say that it was all hooked up correctly to begin with?  It all may have been incorrectly plumbed before you bought it. 

[agav]

My bad - definitely my fault. I confused the two valves. It is exactly as you say - both the fumes from the charcoal canister as well as those from the grommet would have gotten sucked into the Solex. I simply thought that since I don't have a hookup on the Weber for those, I'd bypass it - obviously not understanding what's going on. I read up on emissions control and EGR and cannister and get it now.

However - if I do not have such an input on the Weber - what to do with the existing lines? Can't just cap off the purge valve since the fumes will have to be escaped to somewhere...

[s class]

I have converted a 1980 280S to run K-jet.  It is a HELL of a job. 
- need to replace the hard fuel lines running the length of the car with the K-jet version
- complete wiring harness transplant including fuse box
- this means entire interior out including dash out
- need a K-jet head
- need K-jet manifold, fuel distributor, etc etc etc

The true conversion cost about twice the value of a really good 280SE. 

[UTn_boy]

SCLASS, it seems I wasn't too far off, huh? 

AGAV, you can cap off the purge valve, but you'll have to figure out a way to vent the fuel vapors.  Either to the outside or back into the intake, but the intake method has to be somewhat metered/controlled. 

It doesn't look as if Weber made provisions for this vacuum connection.  Since the connection is direct manifold vacuum, I suppose you could tap into the intake elsewhere, but the tap must be of the same inner diameter of the one on the Solex.  If it's too small it won't work, and if it's too big it'll act like a massive vacuum leak.  If you do this, you'll need to cap off your new grommet, as well. 

[ronw123w124]

Nice thread! I have been following this since my mechanic gave the death sentence on my Pierburg 4A1. I'm torn between this Weber conversion and the Holley conversion. All I'm really after is the drivability of the car after the conversion, fuel consumption is not much of an issue since I use my W116 sparingly speed is also not mch of an issue since I only use the car on leisurely drives.

[ptashek]

I have converted a 1980 280S to run K-jet.  It is a HELL of a job. 
[..]
The true conversion cost about twice the value of a really good 280SE.

Wow, a hell of a job indeed. And here I was thinking it may just require K-Jet fuel lines, distributor and engine harness.
So the only real option of reliably maintaining those carbed cars is what Agav is doing, a conversion to a more modern carb?

[agav]

Little update: I capped both the vacuum ports on the Weber and started her up and she starts up and I can put her in gear and move her around in the garage for now. Haven't take her out of course, given that not all has been set up yet, but hey - high five.

I'll figure out the emissions systems after this.

I need some help matching the vacuum lines back up the the Weber though. I am posting two photos below - the ports I have on the Solex right now and the disconnected lines on the Weber.

For reference here the Weber manual (scanned it):
https://www.scribd.com/doc/302483896/Weber-Conversion-Kit-K248-Manual

A couple of thoughts:

• The big "multi-T" vacuum piece (C) connected into the Solex on one side and then into both the fuel return valve as well as the vacuum governor on the Solex, both of which I no longer have, so I'll cap those off for sure. It also runs to a couple of other places from that T piece.
• I'll check the EGR valve for vacuum leaks in the diaphragm but will then cap it off as discussed before.
• It does not seem as if my distributor has any vacuum connection - so no vacuum retard or advance and I don't see any place to hook those up either. I would expect a vacuum diaphragm on the outside too if it had vacuum controlled advance / retard which is not there. Did these cars come with non-vacuum controlled distributors?