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Need a litttle DGEEEV help

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texas_bugeye

texas_bugeye

Jedi Knight
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Well I give up I'm not a carb savy guy I admit it
I need some help with jetting this thing to get started.
so here my story I have a 948 of unknow orgin.Engine was rebulit 30 over it has a mild cam M22 Isky quite possibly a mistake but.. A stock 948 head redone.
And of course the DGV. I have been tinkering with the eng for a while now and found my Dizzy the org. one was a mess.
I replaced it with a new unit with the pertonics pickup.
Whoa major improvment! Now that end is cleared up I need to get the carb in order. It seems to run rich and doggy on the top. It came setup for a 1275. Idle is best at about 2.25 turns out. I have an assortment of jets and airtubes but dont know where to start.Help? /bcforum/images/%%GRAEMLIN_URL%%/cry.gif
AN5L 8160
ENG.9A-U-H 20850
 
Go down with the main jet first and get it wind up good. The screws are just for idle, nothing else. If its not right when wide open throttle then change the jet. I need to go down one jet size on mine right now. Its a bit rich and aways has been, but then this makes it pickup better from low rpms under load.
 
OI!!! Radu! Welcome to the forum!


Yeah, Chris, start at the main jet. 1275 would have a larger one than you'll need. I'm kinda thinkin' the idle jet may need attention too. 2-1/4 turns out on the screw seems a lot... but I'm a DCOE guy so don't take this too seriously. /bcforum/images/%%GRAEMLIN_URL%%/wink.gif
 
I would start by getting an air fuel gauge, even somthing that you could remove later after you get the carb right. It takes all the "guess" work out of it. Just my opinion, it worked for me.
 
As stated above, the adjustable mixture screw is only for low speed (idle) settings. It does basically nothing past about 1200 RPM.

As the other guys have suggested, look at the main jets. There is a primary and secondary main jet. These jets make the real difference for 90% of your running.
Be sure the accelerator pump is squirting properly too.

This web page will list the DGV internal parts:

https://www.webercarburator.com/carbdetails//explviewparts/DGV5A.pdf

You need to look at parts #24 and #24A. The orifice in the jet (the actual hole) is probably the wrong size. If the hole is too small, it makes the car run lean...if it's too big, the car will run rich.
A decent way to check mixture is to do a "plug chop". This means to run the car up to high speed (top speed if possible, but as high as you can get away with). Run the car like that for several minutes. Then press the clutch in and shut off the engine (be carefull not to lock the steering wheel if you have a lockable steering column!).
Do not allow the engine to slow to an idle before truning it off. Coast to a halt and pull to the side of the road. Remove the plugs right there and look deep into the "cone" around the center electrode. It should be a light to medium tan colour.
Truthfully, you should discard the plugs each time you shut down and replace with fresh plugs.

In the old days, racers would solder up the jets and just drill them out to a smaller size and do a test run. They'd keep removing the jets and re-drilling them with slightly larger holes until the car ran good.

There is some decent info here too:

https://dimequarterly.tierranet.com/articles/tech_weber_tuning02.html

I just bought a car (MGB) with a DGV. My ultimate solution will be to fit a set of SUs to it.
 
Thanks for all the feed back. I have a few days off between now and xmas and 2 are slated car days.I have some jets that came off a DGV I had on the cortina I think I'll Solder them shut. Then take the car out on the current setup and do the plug chop test. then decide were to go from there. Do both the primary and secondary jets affect the full RM range or does the secondary come in at a higher RPM like the old holleys.
 
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