solex to q-jet conversion question. - PeachParts Mercedes-Benz Forum

72-250c · #1 05-02-2012, 10:40 PM

i have read and searched everything here and have decided to scrap the solex on my 1980 w123 250t in favour of a q-jet. i know that i will be using an after market air breather, so, what do i do with the crank case vent tube coming off the valve cover? how have others solved this small problem?

t walgamuth · #2 05-02-2012, 11:07 PM

you need a place to put it into the air cleaner. Possibly a fitting from the hardware will work. drill hole bolt in a barbed fitting for the rubber hose. i put a q jet on my 3 liter bmw engine. It required the jet probes from a 68 pontiac sprint to run correctly. I suggest an edelbrock q jet replica. it should be a higher quality than the old q jets themselves.

72-250c · #3 05-03-2012, 08:31 AM

the original air breather had a small cup to seperate any liquid from the dirty air as it passed through to be sucked back through a vaccume port on the base plate at the back of the carb. so, just put this dirty air from the valve cover into the breather. i don,t bother to try to seperate the water from dirty air? and i plug the port that was designed to take the seperated dirty air into the base plate?

metering rods and jets are as you mentioned. someone, danwatt, drilled holes in the primary buterflys but did not specify how many or what size.

t walgamuth · #4 05-04-2012, 11:09 AM

Separating the sludge from the air is probably a good idea but if the engine is in pretty good shape might not be an issue. I am not expert on that. I think in my case I just dumped it in and did not worry about it.

The sprint metering rods should get you very close. I would be very reluctant to start modifying the carb parts until all adjustments and metering options have been played out.

I have a Qjet book I used back then. I probably will want to hold onto it but if you cannot find one let me know.

Tomguy · #5 05-04-2012, 11:57 AM

Crankcase blowby will have some moisture and oil in it. I don't know of any modern cars that come with a system to separate this - mainly because it's an added maintenance item. Would quick lube places remember to empty it out? Nope.

That having been said you can replace yours with a quality catch can I'm sure. I have one on my Charger and it works quite well. Although the mounting is specifically designed for the Chrysler Hemi engines (or the V6 depending on the one you get) I am sure you could find or fab a mount easily enough.

I don't know where you're located but these guys are in Florida and I'm sure they'd be more than helpful if you brought your car & asked if there's a way to fab a mount for one of their cans. They give away tons of stuff to the "LX" community and as car guys I doubt they'd turn away a vintage MB

If I had my 4.5 on the road still, I'd have had a nice mount for one fabbed up by now.

Billet Technology Signature Series Catch Can 5.7 or 6.1 Hemi Engines
Billet Technology Signature Series Catch Can 2.7 or 3.5 & 3.6 Pentstar
One of the really nice things about the design is the way they use some type of steel wool in the cap to encourage the moisture & oil to condense into the can.

cefalu · #6 05-04-2012, 12:04 PM

Nothing against a Q Jet, but just curious why you went that route? The Q Jets are wide and the choke won't fit. The Holley was the only carb I found where a choke could fit. The DOHC valve cover is too close and does not leave enough room.

I have a Q-Jet ready for the conversion but want cold start driveability. I just did the same conversion and it was really easy with the Holley.

My 280C has the crankcase breather hose plug into the air cleaner. MBZ never had a separator. I was able to retain the stock air cleaner so you can't tell anything is different.

t walgamuth · #7 05-04-2012, 01:38 PM

The manifold, I believe is a spread bore like the Q jet. It was a perfect fit. I had to redrill two of the base mounting holes. A holly would not have fitted without an adapter for the air flow, and there would not have been room for that under the hod. On my conversion i used a manual choke, which is very compact.

My application was a 74 BMW bavaria with the 3 liter motor.

cefalu · #8 05-05-2012, 01:12 PM

Not true. A Holley Economaster is a Q-Jet bolt on replacement. It is a spreadbore pattern and no adapter is required. The same as a Q-Jet, you have to hog out the two back holes to match the solex pattern. It is the exact same height as the Solex, and the original air cleaner can be retained. It was minimal modification, that's why I went that route.

I just wanted to know why the OP chose a Q-Jet. I have one I planned to try out, but the Holley was so easy and works so well I have not seen the need to experiment with the Q-Jet yet.

t walgamuth · #9 05-06-2012, 05:08 AM

At the time I was working on mine, I don't believe Hollly made a spread bore. If they do as you say, then by all means, use the Holley. Hollies are generally much higher quality carbs than the Quads.

72-250c · #10 05-06-2012, 06:33 PM

I went the q-jet route because a friend had a couple spares kicking around. My engine is the w123, single cam,the carb
is also mounted 90 degrees counter clokewise to the 280 dual overhead cam motor so no issues with the choke. In retrospect maybe I should of went with the Holley 6340 economizer.

t walgamuth · #11 05-07-2012, 07:17 AM

At the time, I believe I was paying about $5 or 10 ea for used carbs to experiment with.

If doing it today i would spend the money for a new quality carb, probably.

cefalu · #12 05-07-2012, 11:19 AM

OK, I didn't realize Your car wasn't an M-110 DOHC. if you have plenty of room next to the carb the choke/cam cover conflict cover isn't a concern.
The Holley economaster 4360 came out in the early 80's as a fuel economy bolt on upgrade to the Qjet. They have been around for about 30 years now. Holley does not make them anymore but you can still find NOS ones on eBay. I picked up a practically new one for $30.

t walgamuth · #13 05-07-2012, 04:59 PM

Quote:

Originally Posted by cefalu

OK, I didn't realize Your car wasn't an M-110 DOHC. if you have plenty of room next to the carb the choke/cam cover conflict cover isn't a concern.
The Holley economaster 4360 came out in the early 80's as a fuel economy bolt on upgrade to the Qjet. They have been around for about 30 years now. Holley does not make them anymore but you can still find NOS ones on eBay. I picked up a practically new one for $30.

I must have just missed the 4360 carb. $30 for a new old stock is a deal!

cefalu · #14 05-07-2012, 06:23 PM

The one I bought was not NOS, it was used, but looks excellent. The NOS ones run closer to $300. Not a screaming deal but OK compared to $1,000 for a Jam Engineering rebuilt one