Weber DGV help please

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06.03.22, 12:59 PM
SHutson

2 Attachment(s)

Weber DGV help please

I'm having an issue with the primary side of my carb being VERY rich - I can see fuel droplets in the venturi and puddling on the throttle plate. I do not believe is it a jetting/emulsion issue as changes to those components has little effect. The carb is set up with a single dump tube on the secondary side, but there is a second dump tube from the bowl well that is connected to a port on the carb top that I can not identify. The online article "Race Prepping the 32/36" shows this port should be sealed. This port is marked with the yellow circle (not my pics).

https://www.apexspeed.com/forums/att...d=103330&stc=1

The port in question connects to the port in the base identified by the red circle. Can anyone tell me where this port goes? My guess is that it might connect to the emulsion well or the venturi feed resulting in my excessive fuel issue.

https://www.apexspeed.com/forums/att...d=103329&stc=1

I don't want to just seal it off without understanding what's happening and/or if this odd dump tube is my problem. Lots of online research has come up blank.

TIA
06.03.22, 2:00 PM
Rick Kirchner

I have a pretty comprehensive book on the 32/36 and those passages aren't identified anywhere in it.

Call an engine builder.
06.03.22, 4:16 PM
mark elder

Originally these carbs had a 'power valve'. An odd thing but it seems to work OK on the street. It takes a bit of extra fuel from the bottom of the bowl and gets it into the engine. This circuit needs to be sealed off for racing.

People do it various ways. In the middle of the bottom of the bowl there is a large brass plug thing. It is threaded and screws in to the bottom of the bowl; you have taken it out (or it was never there...). I seal this system off by sealing the brass thingy; I pull it apart and solder the holes over. Then I loctite it in place. Other folk seal the passage at various points. With a carb disassembled, you can blow into the hole in the bottom of the bowl and see where that fuel was designed to go. I have seen both the power valve soldered and the passages glued shut (with JB weld etc) on the same carb. I think Ivey just glue a passage shut.

Go and examine what you have and report back.
06.03.22, 4:20 PM
mark elder

power valve

https://www.pegasusautoracing.com/pr...asp?RecID=4129

this is the thing that has to be sealed after pulling it apart
06.03.22, 6:47 PM
Rick Kirchner

now I'm going to have to go back and look at the book again.
06.03.22, 9:26 PM
SHutson

Quote:

Originally Posted by mark elder

Originally these carbs had a 'power valve'. An odd thing but it seems to work OK on the street. It takes a bit of extra fuel from the bottom of the bowl and gets it into the engine. This circuit needs to be sealed off for racing.

People do it various ways. In the middle of the bottom of the bowl there is a large brass plug thing. It is threaded and screws in to the bottom of the bowl; you have taken it out (or it was never there...). I seal this system off by sealing the brass thingy; I pull it apart and solder the holes over. Then I loctite it in place. Other folk seal the passage at various points. With a carb disassembled, you can blow into the hole in the bottom of the bowl and see where that fuel was designed to go. I have seen both the power valve soldered and the passages glued shut (with JB weld etc) on the same carb. I think Ivey just glue a passage shut.

Go and examine what you have and report back.

The well in the float bowl is sealed.

I have 4 race-prepped DGVs and each one handles the "dump tube" issue differently. The carb in question originally had three dump tubes, one to the primary, one to the secondary and the odd one to the port I referenced in the OP (the primary dump tube has been removed). I have another carb top that has the referenced tube to the mystery port, but it is pinched closed at the power valve well location, disabling its function. I even have one with two dump tubes handled completely in the carb base. No two carbs deal with it the same which makes it hard to decipher this voodoo.
06.03.22, 9:55 PM
mark elder

I am guessing you have seen this (the original was not complete; this link is).

http://www.thelolaregistry.com/DIY/Weber.htm

The Factory dump tube needs to come out for good (the stubby tube in the pliers in your pics) and yes, the hole needs sealing (circled yellow and then red in your pics).

This Lola registry article is pretty much how most people do this (including Ivey from memory). I must have done about 9 carbs just like this now and they all worked fine except for the second hand one that I missed seeing a crack in the body. The new 1/16" hole dump tubes are fairly floppy and easy to bend by mistake when you take the top off; if they are in the wrong place the mixture is all wrong. Don't use the 3/32" hole size tubes; they flow too much and run rich. You should be able to get your mouth onto each dump tube and blow through them equally.

The secondary needs to be cracked open a bit; adjuster is hard to get to when all mounted up.

When you say the primary is too rich; how do you know? Is there raw fuel visible coming out of some place (dump tube, venturi etc). Is the actual mixture adjuster (side of carb) accidentally closed or wide open.
06.04.22, 8:20 AM
SHutson

Quote:

Originally Posted by mark elder

When you say the primary is too rich; how do you know? Is there raw fuel visible coming out of some place (dump tube, venturi etc). Is the actual mixture adjuster (side of carb) accidentally closed or wide open.

Yes, instead of a nice "mist" in the primary carb throat, there are visible droplets of fuel jumping around and puddling on the butterfly after cutting the throttle. Its source appears to be the primary venturi (which I changed with no improvement). No dump tube in that barrel, so no other source for the fuel. The secondary side seems fine. I had my smallest main jet (145), largest air corrector (185) and leanest emulsion tube (F50) in that barrel yet I still had too much fuel.

Some person, or persons, must have thought adding that extra dump tube to the mystery port/passage was beneficial, since two of my carb tops have it. I thought someone here might know why so I could see if that's my problem. At this point I'm going to try and lean out the primary side further (I just received the bits to do that), or, if that fails, rebuild a different carb.

P.S. I now believe that port/passage was cast into the base for a potential primary-side OEM dump tube since that appears to be the function of the port/passage on the secondary side. If so, it would have no function on the primary side and would not be open to the emulsion well or the barrel. That doesn't explain why someone would connect a dump tube to it, but........
06.04.22, 5:26 PM
Jim Garry

A month ago I had raw fuel pouring thru my DGV. Turned out it was a fuel pump issue. It was a mechanical fuel pump from Dave Bean Engineering. Supposed to be stock except for the fittings. Finally put a gauge on it ... 15 to 20 psi!

Bean took it back. Said it was one of the last of a batch of bad pumps.
06.04.22, 7:19 PM
SHutson

Quote:

Originally Posted by Jim Garry

A month ago I had raw fuel pouring thru my DGV. Turned out it was a fuel pump issue. It was a mechanical fuel pump from Dave Bean Engineering. Supposed to be stock except for the fittings. Finally put a gauge on it ... 15 to 20 psi!

Bean took it back. Said it was one of the last of a batch of bad pumps.

Yeah, that was my first thought. I'm also using the Ford mechanical pump, but I checked and I'm at a solid 3psi at all revs.
11.17.24, 7:18 PM
Pdx2sxm

Quote:

Originally Posted by mark elder

I am guessing you have seen this (the original was not complete; this link is).

http://www.thelolaregistry.com/DIY/Weber.htm

The Factory dump tube needs to come out for good (the stubby tube in the pliers in your pics) and yes, the hole needs sealing (circled yellow and then red in your pics).

This Lola registry article is pretty much how most people do this (including Ivey from memory). I must have done about 9 carbs just like this now and they all worked fine except for the second hand one that I missed seeing a crack in the body. The new 1/16" hole dump tubes are fairly floppy and easy to bend by mistake when you take the top off; if they are in the wrong place the mixture is all wrong. Don't use the 3/32" hole size tubes; they flow too much and run rich. You should be able to get your mouth onto each dump tube and blow through them equally.

The secondary needs to be cracked open a bit; adjuster is hard to get to when all mounted up.

When you say the primary is too rich; how do you know? Is there raw fuel visible coming out of some place (dump tube, venturi etc). Is the actual mixture adjuster (side of carb) accidentally closed or wide open.

Bringing this one back. The lola registry link doesn't work, and I'm really looking for some photos of the dump tube install!
11.20.24, 1:03 PM
redcar9

Quote:

Originally Posted by Pdx2sxm

Bringing this one back. The lola registry link doesn't work, and I'm really looking for some photos of the dump tube install!

I just sent mine to Ivey for rebuild.
https://iveyengines.com/
05.22.25, 4:59 AM
Peterman63

3 Attachment(s)

I found a few photos of a dump tube installation in my computer, downloaded from somewhere (it might be from Lolaregistry a long time ago). My carb doesn´t have it and i´m thinking about give it a try.
Looks pretty straight forward.
General advise is to use 1/16" tubes, which must be inner diameter, right?
On the photo of the installation, there are 3 tubes going down the bowl but i can only see one in each port. Where is the 3rd tube
going?

Cheers
/ Peter

https://www.apexspeed.com/forums/att...d=115498&stc=1 https://www.apexspeed.com/forums/att...d=115499&stc=1 https://www.apexspeed.com/forums/att...d=115500&stc=1
05.22.25, 7:47 AM
Pdx2sxm

Interesting! Thanks!