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Weber 32/36 DGV Tuning

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pauleh317 Avatar
pauleh317 Paul Holyfield
Yakima, WA, USA   USA
1980 MG MGB
Hi all,
I have a 1980 MGB that had a Weber 32/36 DGV when I got it. I was doing some work on it and wanted to make sure the carb was set properly. I have followed the directions on the redline/weber website and I am not sure I am correct.

I started with a warm engine and set the idle and mix screws as they should be according to the instructions.

Set the Idle stop screw (speed screw see fig 1) by backing out the Idle speed screw until it is not in contact with the throttle stop lever. Cycle the linkage again to be sure that the linkage comes to close without any assistance. (Checking for linkage bind) Now bring screw back into contact with the lever and continue to open or screwing in 1 turn no more than 11/2 turns.

Set the mixture screw (see Fig 1) by first screwing in until the screw stops, bottoms out. Back out the screw 2 full turns.


At this point the engine will not stay running so I have to adjust he idle in another turn or two. When I do get a rough idle and start to adjust the mix screw it ends up running best with the mix screw almost all the way seated or out maybe 1/4 to 1/2 turn. This just seems not right. I have checked for vacuum leaks, but have not found any. The only vacuum hoses I have come from the port on the base of the carburetor to the vacuum advance on the distributor and another from a port on the manifold to the brake boost.

My timing is set to 10 degrees btdc.
Any ideas would be appreciated.
Thank you all.

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Sinewave Avatar
Sinewave T. Keith Vezina
Kenner, LA, USA   USA
Sounds like your idle jets are too large. A good starting point is:
Primary idle - 70
Secondary idle - 65

Check the size of your mains, should be something near:
Primary main - 150
Secondary main 145



T. Keith Vezina
British Motoring Club New Orleans
1976 MGB, 1976 MGB Trailer & 1967 MGB MK. I

sws615 Avatar
sws615 Stephen Struck
Grand Haven, MI, USA   USA
1967 MG MGB GT
1975 MG MGB "Commission # G23N124120"
2015 Acura MDX
Once you get the jets sorted and the car idles well, don't be afraid to advance the timing. I can't give you a number, but years of experience have shown that my roadster runs better with the timing advanced more than the local LBC garage set ti up with.

FWIW, I also believe that Webers run better when set pretty lean. Again, the LBC garage set it too rich; runs very well after some tinkering to the lean side. Good luck.

Steve

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jdriley83 Avatar
jdriley83 Gold Member David Riley
Macon, GA, USA   USA
1976 MG MGB "Reluctant"
What was the car doing before you started adjusting the carb?

Stock idle jets are 55 and 50
Stock mains are 140 and 135


Attachments:
3236DGV.pdf    385.8 KB

ClayJ Avatar
ClayJ Silver Member Clay Johnston
Mt. Olive, MS, USA   USA
1972 MG MGB
I agree with Stephen, the Weber seems to prefer more advance.

As Keith notes, if your idle is more than 900-950 and the idle-mixture screw is almost closed, the mains are picking up (you're not running on the idle jets). You need a really low idle to properly set the idle-mixture, the lower the better. You might need to adjust the timing up for better/lower idle, 800 is a good target to get the idle-mixture set, you do not want any input from the main jets when setting the idle-mixture.

tvrgeek Avatar
tvrgeek Silver Member Scott S
Bowie, Maryland, USA   USA
1965 MG MGB
Does no one do any SEARCHING before posting? This has been covered ad-nausium.

Stock is set up for a Ford 3.0 V6. Start with Michael C's basic setup. To get more precise, you need real instrumentation. That means either a DYNO or a good wideband O2 sensor.

Disclaimer: On my roadster, I had to go past his setup to change primary e-tube and modified the acc jet. On my GT, it was much closer. Advance probably depends more on what distributor you have. The engine should not care one hill of beans how the charge gets in there, just what it is. More advance would imply incorrect mixture to me.



Cogito ergo sum periculoso

Gremlin Steve G
Antioch, Illinois, USA   USA
Paul,
I had the same problem as you on my 77. I posted on this forum asking how many other weber users actually were taking advantage of a progressive carb and were within 2 turns of idle speed screw contact, no replies.

I once bought an old Weber tuning guide that referenced our problem. The solution in that manual was one I was always reluctant to try but eventually it did solve my problem. I added a wideband O2 sensor to aid in my diagnosis and track my results.

My engine wasn't getting enough air at idle. The weber does not have replaceable/adjustable idle air jets, only an orifce. As the manual instructed, I drilled a small hole in the primary throttle opposite the progression hole side. The idle picked up and I moved up in drill bit size until I could idle with the progression holes still covered. I was then able to adjust the mixture screw and it actually responded properly. Everything fell into place and the O2 sensor proved it.

Do yourself a favor and get an O2 sensor. Then do yourself another favor and get a Schlemmer distributor curved for your setup. Installing Jeff's distributor was the best thing I did for my car. The shop next door to mine is a dyno tuning shop that came over to say "it sounds like I'm making horsepower over here" when I was tuning with that new distributor. It really woke up the car. Thanks Jeff!

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spikemichael Avatar
spikemichael Platinum Member Michael Caputo
Ocean Shores, WA, USA   USA
1973 MG MGB "Freebie"
1973 MG MGB
1974 MG MGB "Spike"
1979 MG MGB "MegaBeanie"    & more
In reply to # 3491426 by pauleh317 Hi all,
I have a 1980 MGB that had a Weber 32/36 DGV when I got it. I was doing some work on it and wanted to make sure the carb was set properly. I have followed the directions on the redline/weber website and I am not sure I am correct.

I started with a warm engine and set the idle and mix screws as they should be according to the instructions.

Set the Idle stop screw (speed screw see fig 1) by backing out the Idle speed screw until it is not in contact with the throttle stop lever. Cycle the linkage again to be sure that the linkage comes to close without any assistance. (Checking for linkage bind) Now bring screw back into contact with the lever and continue to open or screwing in 1 turn no more than 11/2 turns.

Set the mixture screw (see Fig 1) by first screwing in until the screw stops, bottoms out. Back out the screw 2 full turns.


At this point the engine will not stay running so I have to adjust he idle in another turn or two. When I do get a rough idle and start to adjust the mix screw it ends up running best with the mix screw almost all the way seated or out maybe 1/4 to 1/2 turn. This just seems not right. I have checked for vacuum leaks, but have not found any. The only vacuum hoses I have come from the port on the base of the carburetor to the vacuum advance on the distributor and another from a port on the manifold to the brake boost.

My timing is set to 10 degrees btdc.
Any ideas would be appreciated.
Thank you all.

135, 145 mains are not enough, 145 150 are a better starting place with 135 you will be constantly starved for fuel at speed.

Your set up procedure is incorrect.

PLEASE read the skeletons in the closet thread.
The proper setup procedure is therein.

Your idle timing with vacuum disconnected (shouldn't matter anyway since you are using ported signal) is between 13 and 16* BTDC and you should be able to get the car to idle anywhere you want from 650 RPM on up, though 850 is a great idle speed. Your air correction jets at 165 is also a good starting place.

Return spring tension and linear tension are likewise important. Make sure your gaskets are trimmed to the base ofthe carb / manifold, do nto obstruuct the flow out of the bottom of the carb. Make sure you use the hick gasket, it is also thermal isolation as well as a seal.

Once you have it forget it any problems are in the need of a tune-up or someone has fiddled with the timing.

Call me if you have questions I am always happy to help over the phone too.



Michael J. Caputo
'79 RBB and '73 CBB owner with extensive experience in 12v Audio System design and installation.
Vendor of Regalia and Promotional Products. Forum Member with a warped sense of humor.


Member Services:
Pre-Order NOW for shipping in early December! Call me at 978-249-5760 PST for help with your Weber DGV Carburetor, questions about the calendar or just to talk MGBs!
jdriley83 Avatar
jdriley83 Gold Member David Riley
Macon, GA, USA   USA
1976 MG MGB "Reluctant"
I just got my '76 running great after months of fiddling. My weber 32/36 DVG came with a 60 primary idle jet. The mixture screw was adjusted 3 or more turns and the motor would stall at just about every stop sign if I did not add a little choke. I upped the primary idle jet to 65 plus I changed the primary main to 145 and the secondary main to 140 ( from 140 and 135 respectively). This completely corrected my problems. The mixture screw is now 3/4 turns out for best idle and it will start with no choke needed most times (at least with current morning temps). Timing is around 13 deg btdc @ 800 RPM idle.

Document what your jet sizes are before you change anything.
Small changes to primary jets have big effects on how the carb performs.
Completely understand what each jet does and how it effects performance.

In reply to # 3491437 by Sinewave Sounds like your idle jets are too large. A good starting point is:
Primary idle - 70
Secondary idle - 65

Check the size of your mains, should be something near:
Primary main - 150
Secondary main 145

Rick Fawthrop Avatar
Rick Fawthrop Gold Member Richard Fawthrop
Seattle, WA, USA   USA
Don't be afraid to have the secondary jet larger than the primary.

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jdriley83 Avatar
jdriley83 Gold Member David Riley
Macon, GA, USA   USA
1976 MG MGB "Reluctant"
I have a 150 and may put that in the secondary main at some point just to see what the difference is. But the car is running so sweetly right now I hate to mess with it.

In reply to # 3494485 by Rick Fawthrop Don't be afraid to have the secondary jet larger than the primary.

tvrgeek Avatar
tvrgeek Silver Member Scott S
Bowie, Maryland, USA   USA
1965 MG MGB
Don;t be afraid to use actual instrumentation to help dial it in when close. Then go back and tweak the timing as the closer to 14.7 you get, the less advance you need. If you are staying a tad rich for performance, maybe you can take another degree.



Cogito ergo sum periculoso

pauleh317 Avatar
pauleh317 Paul Holyfield
Yakima, WA, USA   USA
1980 MG MGB
Thank you all for the information you have provided. I will be trying some of these suggestions along throughout the summer.

kareski63 Gold Member Peter Kareski
Front Royal, Virginia, USA   USA
1977 MG MGB "Freddie"
I just installed the same system this year on my 77 B. I had the problem you had but with research it was suggested to set the timing at 15 vice 10 at a 1000 rpm. Made a world of difference and I was able to adjust to specs. Make sure you adjust to the starting specs before going to fine tune. I still have a little hesitation upon take off but I am not going to worry about that until I put a few miles on it for break in. Runs like a champ, better than the old Stromberg.

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