Weber 38 DGAS Installed

[mosu]

73 280 M110 with an ex-Solex

The Weber is in! Started right up, on default settings. Cold start RPM was set around 2500, and my squealing belts announced its entrance.

I find it very smooth and tractable. My powerband previously was off-idle punch that immediately lost steam. Now it pulls up hills, in traffic, when passing. Setup was done by ear.

There is a small flat spot that other people have reported. It comes off-idle if I feather the gas. Smaller than what my Solex had, so it's still an upgrade .

I'm going to post my settings and results to leave a reference for others that choose the Weber route. I've disconnected the vacuum-electric shenanigans for vacuum retard and left them dangling for now. Base timing was set at 10 BTDC. I'll slowly creep it up but want to make sure that there's no pinging. From here it's critical to follow the setup instructions to the T. I can't stress this enough, or there will be endless tail chasing later.

I made sure that the ignition is sorted, new plugs (or clean, brown old ones), wires and all that. My old pugs looked great so I left them alone in case I fouled them while setting up the carb. In retrospect, I was being paranoid. Before I started, I disconnected the vacuum retard and set the timing to 10 degrees BTDC. This is their baseline spec. There may be an advance as well on newer models, but I didn't have to contend with that.

I turned everything off, had a cold brew for clarity, and proceeded to tear the Solex off with extreme prejudice. Found a nice puddle of gas chilling in the manifold and immediately thought of a comment that I read on this board: "the Solex is as sophisticated as a monkey with a bucket pouring gas down the intake". So true Lots of crap had collected on the channels under the carb. One looked like it led into the coolant pipes and had collected what looked like a pile of ashes in that opening. Now I know where grampa went . Went to work on it with some respectable chemicals and soon I could eat off that manifold.

Installing the linkage took alot, and I mean alot, of fiddling. I still don't think I have it 100%. The little pivot they provided in the kit barely fit into its sleeve so I had to do some ghetto sanding to allow it to move freely. A throttle return spring is DEFINITELY required. Make it a strong one. I re-purposed the one from the Solex, tied a few of its coils together and attached it to the bracket that holds the brake booster vacuum line. Ugly but functional. The little linkage bit that goes to the carb from the pivot seems to make the whole assembly exceedingly difficult to operate. I have to really stand on the throttle. Nothing is touching or binding, so I guess the little plastic cups have to get worked in??

Before the new carb went on, I made absolutely sure that the baseline settings are followed - throttle stop at 1/4 turn in, and the mixture screws at 1 each. No transition holes exposed, all is good.

Fired her up, and she started as soon as fuel crawled up to the bowl. Ran at a really high cold idle, so I'd turn that choke screw out half a turn in retrospect. Once the engine was fully warmed, it settled onto its idle. 650 rpm from the box, impressive. I fiddled with the mixture screws until I got the smoothest idle, perhaps another 1/2-3/4 turns out from baseline. Then I gave them a little more. Finally, and this is essential to be done now, I went after the throttle stop. Bumped that to 670 rpm, went over the mixture screws one last time and it's done!

I drove home and everything was smooth as butter. I saw the flat spot, but only if I didn't give the throttle a confident prod, and mostly when coasting to almost stop and picking up again. I suspect the accelerator pump jet may be too small out of the box. Light, long throttle inputs just don't provide enough juice. More sudden ones do.

The last thing left to sort out is cleaning up the engine bay of the stray vacuum lines and finding a more secure spot for the fuel pressure regulator. I reused the one from the Solex, so it's floating around hung up on three fuel lines. Oh, and did I mention the stiffness of the throttle?

Any thoughts on that? Nothing is binding, and if I disconnect the little piece that goes to the carb throttle, it feels fine. Once I connect that, I get the heavy pedal. It's going to the carb at a 20 degree angle from the crank, but I'm not sure that's a problem. Have other Weber owners experienced this, and how did they deal with it?

I hope this little rant helps others considering a Weber upgrade. It's a beautiful carb, and with a little bit of patience I think it can be tuned to perfection.

(Pics coming soon!)

[mosu]

UPDATE:

Linkage issues are solved, the spring was too stiff. A Help! Pack of throttle return springs later I found a better one. Stiffer than stock, but tractable.

Once the first drive high wore off, I noticed the flat spot. After a couple of calls to Redline technical support, I ended up advancing the timing aggressively to raise the idle so I only use about 2/3 turn on the throttle stop screw. Any less than that and she’ll die. Guy on the tech support line claims that more than ½ turn exposes transition holes, but I don’t buy that. Car just won’t idle right under ¾ turns even with aggressive timing. If anyone has a shelved DGAS, can you please confirm how many turns of the throttle stop screw does it take to expose the transition holes?

This minimized the flat spot to almost imperceptible on flat road. On a low speed, off-idle ramp start it is present and pronounced. I am suspecting the ignition advance is coming in late. No vac advance to help it under load. All of a sudden I have a low-vacuum, high-fuel condition with insufficient advance. If there revs are high enough, there is no flatspot, even o a ramp.

Distributor is stock for a 73 280. I am thinking of popping a Petronix/Hot Spark module to get rid of the points. Any thoughts on improving the advance curve? I need more advance at lower revs, tapering off sooner. I think max advance if fine for now.

On another note, would a noisy chain impact timing in any way? Less than 1 degree of stretch at the crank, but I’m guessing that it’s not as tight as it can be while running.

Let’s get a discussion going, guys…I know that some people went down this road with mixed results. I think that it’s worth a second look, so I’m contributing everything I find in order to get these beautiful machines running right.

[alulai]

I enjoyed my weber! I am really glad you liked it too!

[bluebenz]

On my 280C, I had installed a weber 38DGES from redline to replace the problematic solex, but was never able to completely get rid of the flat spot. The car started, idled, and cruised very well but the flat spot was hard to live with. Redline was of no help at all!

I sold the car in 2008 with the weber and solex, not sure what the new owner did. I hope you can solve this issue.