Weber DGV Baseline Jetting

[Dickf]

I have dual Weber DGV carbs on a 73 240Z with a stock engine other than a slightly modified cam. I beleive that someone has done some re-jetting of these carbs in the past because they do not appear to have the stock jets.

Since the car does not run particulary well I am in the process of trying to re-jet these, and was wondering what jetting others are using with these carbs to help me establish a baseline as to where I may need to go.

I realize that I won't be able to solve all of my problems by just slapping in whichever jets others are using, but I hope to save myself some time in the test and evaluation process by obtaining some baseline information.

Thanks.

[senkyoshi]

It would be great if you could tell us what jets are curently being used in the carbs. Also check timing and ignition. When you say "the car does not run particulary well" what do you mean? Check your spark plugs. Are they black? white? brown? What kind of gas mileage are you getting.

I also have Webers (DGV) and have been working on getting mine running well and am almost there.

Good luck!

[Dickf]

Senkyoshi:

Plugs are black. Gas mileage is poor. Timing is good.

I know that the Mixture is rich.

Present jetting:

Mains: 132/145

Idle: 55/60

Air Correc.: 160/170

My understanding is that the Carbs would have been delivered with the following jetting:

Mains: 140/135

Idle: 55/50

Air Correc.: 165/160

As you will note, with the carburetors as delivered, the secondary jets are always smaller than the primary jets; whereas the jetting on my car is just the opposite.

What jetting are you running?

What process have you gone through to get yours running well.

I haven't started changing anything, yet. I'm trying to get the information in order before I tear into it. I've read the Weber Haynes Manual and Pat Braden's Weber Book; and I've searched the internet looking for information. I've also surveyed the existing conditions of the carburetors and I've checked the engine with a Colortune.

Tentatively my process will be to work from the primary idle circuits through the progression circuits to the main circuits.

Any guidance will be appreciated.

d***

[senkyoshi]

I will be able to help you some more when I get home from work tonight. Have you synched the carbs? If the carbs are not synched then changing the jets will have little effect. I will try to post some more help tonight.

[71ZZZZZ]

You might try giving the guys at Top End Performance in North Hollywood a call, they are Weber distributors and have a couple of rebuild kits that are correct for this carb set on a Z

http://www.racetep.com/rebuildrejet.html

...I'm planning on taking mine in for a rebuild shortly(no time or knowledge to rebuild/jet myself)...I know this carb set doesn't seem to get alot of good press but I've not had any problems with mine over the years...good to see other users...

:beard:

[senkyoshi]

I tried to post last night when I was home but I couldn't get on the site. I could get everywhere else on the net but not here. Was this site having problems last night? Now I am at work again. Here is what I remember about my jetting.

Main:115,120

Idle:45,50

Air:170,175

I think those are whats on mine. I also think I am running a little lean. I am still working on them. Remember that you need to synch the carbs as well. All the jets in the world will do you no good if the carbs are not synched. Do you have a synchrometer and DGV adapter? Do you have instruction on how to synch them? VERY VERY helpful.

These are good carbs they just take some time getting right. There have been a few times that I have almost given up and gone to SUs but I am glad I stuck with it. I have learned a lot in the process and I have a feeling of accomplishment instead of giving up.

[Dickf]

I have a synchronometer with a DGV adaptor and I have sunched the carbs. Of course, as I start making changes I will have to be re-doing all of that.

Interesting comparison between your jetting setup and mine. You're running significantly smaller jets than I am.

I'm running rich whereas you are running lean wich would be expected.

Also, your jetting is across the board smaller than these carbs "as delivered" and my jetting is across the board larger.

How did you get to this point with your jetting?

What kind of gas mileage are you getting?

[senkyoshi]

Right now I am getting around 21-22 MPG. The way I got to where my jetting is at is going down increments of 5 to 10. For example, I started with 140 main and went down to 130 and then went down by 5 until I got to where I am at. Same thing with the Idle jets. Also, my timing was around 5 BTDC and I took it to about 16-17 BTDC. It is running alot better now. If anyone else sees anything that I am doing wrong let me know. I am still learning too.

[Dickf]

I had the opportunity yesterday to do some more "research". I swapped the idle jets (primaries for the secondaries). The primaries had been 55 and the secondaries 50. I'm now running the 50s in the primaries and the 55s in the secondaries.

It's better, but still very rich. Presently the "best lean idle" is at 950 RPM with the Mixture Screws at less than one turn and the Idle Speed Screws at 0 (no turns).

I'm in the process of ordering more jets.

[ezzzzzzz]

Sounds a lot like the float(s) aren't set right. A high float will allow excess fuel into the emulsion tube area and dribble into the venturi. No adjustment will correct that.

[Dickf]

Took the carbs apart again over the weekend and the floats are at spec.