I have a question about a Weber 36...

[StefanLee]

So I have a Weber 36DCD (as far as I can tell) on my GT, and it was already installed when I bought the car.

Today, when I fabricated a new gasket between the air box and the carb, I figured I would check the action of the carb without the filter. I figured I had to since I yanked the throttle and saw that fuel only spurted into one barrel (hey, there might be a blockage somewhere...).

I started the engine, and quickly saw that fuel only atomized in one barrel, and the other one was bone dry. Hmmm strange! I could see no fuel in the barrel closest to the engine even when giving full throttle.

I removed the top including the floats and unscrewed the small siphon thingy in the center between the barrels. Imagine my surprise when I saw that it instead of being blocked only had a hole to one barrel, even though the casting was so to say bi-directional (one spout into each barrel).

Is it supposed to be this way? Well I imagine so (since it was cast that way), but it feels that it is a bit unefficient... Is fuel getting into all four cylinders (one barrel should supply two cylinders each, right?)

Carburetors is a new experience (have only dealt with injections before) for me so pardon me if I am asking a seriously stupid question hehe.

Please enlighten me on the inner workings of a 36! (and I DID use the search button, but couldn´t find any info)

Stefan

[GTJIM]

Yep - they work like that. Most 32/36 DGAV Webers have a primary barrel (the small one that squirts) and a vacuum operated secondary barrel (the big one with no accelerator shot).

There are a few configured with mechanically operated secondaries and/or secondary barrels with accelerator pumps but generally they do not.

Just check to see if the secondary barrel butterfly opens when you work the throttle - if it does not you have a vacuum operated secondary barrel carb .... and all is well. Both barrels supply all four cylinders - the big one only opens when manifold vacuum gets high enough to open it and that does not happen when reving an unloaded motor. Just like the secondary barrels on a 'vacuum secondary' Holley four bbl carb ....

Hey! Carbs are so much simpler than the electronics of fuel injection.

[RallyBob]

Yep - they work like that. Most 32/36 DGAV Webers have a primary barrel (the small one that squirts) and a vacuum operated secondary barrel (the big one with no accelerator shot).

Tsk, tsk Jim, you should know that the 32/36 DGV Webers all have mechanical secondaries! True, there is no pump shot on the secondary barrel, except for the rare 'double pumper' models with a secondary vacuum-operated accelerator pump. But the actual linkage is purely mechanical, unlike the majority of the Solexes that Opel supplied on US cars (early US 1.9 Solexes had mechanical secondaries as well).

Bob

[GTJIM]

Learn something everyday on here!

I have only had one 32/36 Weber ... which I ditched for a pair of DCOM's
Guess I should have looked at it a bit more carefully before asuming it worked just like Solii .....

Thanks Bob

[StefanLee]

WHEW!

Thanks guys. So, ALL the fuel is released through the primary barrel then? (and only air in the secondary) What worried me was that I could see no fuel at all in the secondary barrel, even at high revs. Completely dry.

Is it working as it should?

Stefan

[namba209 (R.I.P.)]

Not really, when the secondary barrel is opened up it begins to draw fuel through its main jet and atomize in the venturi. There should be a small hole in the venturi right about the same plane as the butterfly valve where the fuel comes out. HTH.

[StefanLee]

Yeah Namba, that´s what alarmed me a little and the reason for my post in the first place. I couldn´t see any fuel being ejected in the secondary, lower down (the venturi).

Could be blocked or something, looks like I´ll have to do some carb TLC tomorrow.

The hasn´t felt all that powerful, now I guess I´ve found out why. So now it basically runs as a single barrel.

Stefan

[kwilford]

So I have a Weber 36DCD (as far as I can tell) on my GT, and it was already installed when I bought the car.
Please enlighten me on the inner workings of a 36! (and I DID use the search button, but couldn´t find any info)
Stefan

I suspect that is because few of us have ever SEEN a 36 DCD. I had to google it, and found this useful illustration:
Weber 36/36DCD - 28/36
and the parts list
Weber 36/36DCD - 28/36
It looks like the 36/36 is a synchronous carb (both throats open at the same time) like the 38 DGAS, unlike the DGAV which is "progressive" (only the primary throat opens until about 2/3 throttle then the secondary catches up). It appears the throttle rotation is correct (not reversed like a DFAV or DFM). There is also a variant called a 28/36 DCD, with a smaller primary throat, and it is a progressive carb. It seems to be popular Fiat carb, but also for Volvo's, as these Volvo board talks about:

DGV series Weber are not ideal for Volvo motors, these units were built down to a price, the DCD series work a lot better and is better made, this is an older carb from the 1960’s,it avoids some problems that the DGV carbs have (too complicated for my understanding), its more tuneable, has a completely separate starting choke arrangement and removable chokes, (Weber carbs have a throttle body of a certain size, say 36 mm and then a choke inside this which gives the actual opening say 28mm, these sizes can be changed for tuning purposes)

The recommendation was to use the 36/36 DCD, however these are quite rare in NZ and generally come off Fiat 1100’s which would be jetted completely wrong for a Volvo B20+.

The 28/36 DCD is quite common in NZ having been fitted to Ford 1500GT’s; as this carb was also fitted to 2.5litre zephyrs it’s probably big enough.

Question for Topi (or anyone else) - Is the Weber DCD36-36 that much of an improvement over the DGV? The fuel injection worked great for 15 years, however, the DCD would be a lot easier to install.

Re: B20 Bang for the Buck[ALL/1998] posted by Topi on
Monday, 15 December 1997, at 10:11 a.m.

YES- DCD 36-36 is the best and suitable for big, strong vacum signal motor. It doesn't have that "power valve" which gets messed-up on the DGV. DCD is the carb sold in Europe for Volvos, Opels and other conversions. You can trick your DGV but it takes time and will never be as good as DCD. Start with to drill 2mm hole to the primary butterfly. That will reduce vacum through the idle circuit and help idle mixture. I did drill new idle & low RPM passages to the carb body, too. Then, solder bottom power valve to blind. This way all fuel goes through the main jets. You should have around 155/185-195 mains for B20. More if more HP. The other thing is to make a long moving throttle linkage. All kits come with way too rapidly opening linkage. The best is Japanese-type "half wheel". This opens primary slowly and secondary faster. It uses cable, too. Your DGV hesitation may be too low fuel level. Raise until it starts to drip, and then back of 1mm.So- if you go to DCD you don't need to do any of this....ipd used to sell Holley-Weber kit which is the same as Pinto 2.3. Even this 2.3 carb from junkyard works better than DGV and the jetting's pretty much right! They go for $ 10 & up here...In 1984 I did the first CARB (California Air Resources Board) 32-36DGV Volvo kit development (CARB #D-145) and learned more than I care about DGVs...I wanted to certify DCD but the customer, Swedeparts, wanted to make"as much money as possible", rather than having a kit that actually works.

These guys prefer DCD's over DGV's. I learn something new everyday...

[StefanLee]

Sheesh, this is getting complicated! Yes, it is a DCD, and the flaps open at the same time.

I need to look into the lack of fuel in the secondary barrel though.

Stefan

[RallyBob]

Sheesh, this is getting complicated! Yes, it is a DCD, and the flaps open at the same time.

I need to look into the lack of fuel in the secondary barrel though.

Stefan

Probably just dirt. Remove the secondary main jet and blow out the passages. Also, remove the secondary auxiliary venturi and do the same. I've seen dirt/sediment/rust in there before, and in one case a blade of grass which blocked the passage of fuel!

Bob