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MG MGB Technical - Weber 32/36 DGAV

Hey Guys- On my 1969 MGB GT, I have 32/36 DGAV. Fuel pressure around 2-3 lbs; new float needle/ valve seat. Won't idle; secondary barrel provides great acceleration and under-load performance. Tried adjusting the idle (primary side)- won't idle well. Came off a Volvo- should I be looking at jet sizes? Or something else? Thanks, Lee
Lee Kosow

Lee. Yes, you need to look at the jet sizes and see what they are. You also need to clean the carb throughly and install new gaskets (a "rebuild kit") after doing so. I have seen similar problems with the Weber which required a through cleaning and re-gasketing. Post what jets you are running and check the archives to see what it contains on Weber DGV series jet sizes. I have a spare carb I can pull apart if we cannot find the standard jet sizes anywhere else. My daughter wanted a manual choke carb rather than an electric choke carb, so I have a spare until I get the next car up and running. Les
Les Bengtson

Les- I just dipped and cleaned scrupulously, an old DG Webe32/36 I had from somewhere, to makedo while I sent out the HS4 for rebush. I adjusted the idle mix at 2 full turns, hooked up the 02 sensors and got a slightly rich mix in another 1/2 turn which held steady up the rev range. This was my first play with the Weber and it seems to be running strong. I tossed the "progressive" and used the simul-lingage, and I dare say the carb feels snappier and "slightly" more powerful than the SU's. No flat spots, and idle ( 285 Piper, with rollers) is just barely lumpoid. Does anyone make a stubstack for these? Finally, I'll assume old jets were sea level configured, but at my 6700 foot elevation and K $ N filters, I'm thinking its about right.Any reports out there on the "Outlaw" being offerred by Bob at BriTTek??
vem myers

Vem: http://www.pegasusautoracing.com has DGV stubstacks but they are quite expensive. What jets are you using? I assume they are the same for each choke. You should have at least 180's if you have also had some headwork.
Terry

Vem. I have not heard of anyone using the Weber 38/38 carb that Bob is selling. Since I already have a 32/36 on my 79, I may well give it a try and write it up. My engine is .040" over with a stock CB cam a Mike Brown cylinder head and Peco header and exhaust system. The DGV is still progressive linkage. It meets Arizona emissions standards every year, but does not really begin to pull properly until the second barrel of the carb is opened. The single 32mm venturi is just not large enough to provide the fuel the engine wants. I had planned to swap over to a set of SU HS-4s for testing next fall, but it would be very interesting, and easier, to see what the 38/38 is capable of doing. When I have time to do it and do some testing, I will post the results. A fellow from California (Bill ???) originally mentioned the use of the 38/38 on the BMW 2002 models with good success by friends. It would be interesting to see what one would do on a B. Les
Les Bengtson

Les- Holding my breath for your report. So far, I am surprised at this "makedo" and it may become a fixture. The "outlaw" offers significant, synchronous volume increase potential and may be worth a 300 dollar bill.Terry-Thx for the lead.V
vem myers

Terry- No Luck. How much and how are they called. I spent a while and got nowhere and didn't want to spend the day on cat-download. Why you recommend the 180/180. Remember, you are talking to an idiot here...I only know SU and have used the Weber in my lifetime only for excellent outdoor grilling results and nothing else.
vem myers

I have tried the 38/38, from Brit-tek. Very nice set-up, and acceleration is much more snappy, rather than having to wait for the last third of travel to wait for the second barrel to open. I have an O2 sensor that tell me I am a little rich for a stock cam, mild head work. You can reuse the old manifold, it just needs opening up. Not sure if you care, but I got 35 MPG with the 32/36 and about 28 with the 38/38, but still leaning the mains out.

Shareef
Shareef Hassan

Vem:
I'll check my Pegasus cat tomorrow at the office and get back with more info. I seem to recall the stub stack is, hold onto your hat now, about $140. Only worth it for race apps., I'm sure.

As to the jets, the standard setup is 140 primary main and 135 secondary main. Satisfactory for stock B's but I know you upgrade all your B's to a higher performance spec. I'm running a DGEV with a Piper 270 and some basic head mods. Talked to the folks at Top-End Performance, described the engine, and they put together a jet kit (all 6 jets) with 180 for the secondary and 150 for the main,cost $35. Noticeable increase in power and no bog on full throttle. Your engine is considerably hotter than mine so if you are using stock jets you aren't getting all the carb has to offer. 180 jets may a good starting point for your sync-linked carb but maybe 170's or 190's would work better. You may want to check out Topend for yourself and get REAL expert advice. http://www.racetep.com

Again, not sure which jets you have now, but certain some rejetting could pay dividends.

And for an "idiot" you certainly have posted some good info here for the last several years and I've learned a lot from you. So I guess I'm idiot, second class!
Terry

T- Thanx you for the kind words, but my Web-idiocy hasn't changed yet. Got reply from Peg-Sales. Horn is $270!!! with no provision for filters!! I'm gonna consider bastardaptation of the 1 1/2 mini-stacks from the old SU a see if I can create a FrankenWeber. Did the quick math on 38/38 and their area is essentially same as 1 1/2 SU. Shareef's testimonial continues to make that $270 bill look smaller compared to HS6. Lately, and in the archives, the considered opinion steers us away from the DGV:" its a moderate performer, and really just an economy carburetor". Well, I'm impressed, and after all those crusty years, that's hard to do. If precise jetting can further improve this bad boy, more the better.Finally, Shareef, I feel all facts, figures, costs, mileage, that you can include are valuable. V
vem myers

Lee,

Vacume leaks and improper timing will affect idle. My stock 79 "B" also has the 32/36 weber. After I rebuilt the carb, I was not satisfied. I contacted Top-End Performance, discussed my vehicle, and ordered new jets to match my engine. My idle improved, and the lag off idle I experienced dissapeared. I strongly suggest visiting your situation with them. My expierice with Top-End was a good one.
Thomas Nolan

Checked my year 2000 cat and the price was $240. Hard to believe but it really is a low volume specialty piece used for racing apps. It always amuses me to hear the DGV referred to as "just an economy carb" when it is used in several racing classes, most noticeably in Sports 2000 and Formula Ford 2000. These 2 litre engines put out 140 to 150 HP with the Weber-of course this is with sync-link, careful jetting, ram-air and that $270 velocity stack. Pete Burgess has stated that he sees 1 or 2 HP MORE on his dyno with the "economy" progressive Weber over dual SU's on MGB's. (He still prefers SU for originality and throttle response). Another advantage I can see for the SU's is the relative ease of fitting cold air induction- there isn't enough clearence for this with the Weber. The sync-link sounds good for high performance engines like yours and could very well improve initial throttle response but the progressive linkage works well for stock or moderately tuned engines. When I want max power, I always floor it anyway and this opens both chokes nearly simultaneously. And the part throttle fuel economy when cruising even at 70 MPH is impressive.

I hope you get a chance to try the 38 on your engine and report on the improvewment. I've heard from carb experts that the 38 can be considered as the downdraft performance equivalent of the sidedraft 40.

Finally, anyone using the Weber can get more air flow though the filter by using an oval air filter with the element also exposed at the top from ITG or others in place of the small rectangular stock K&N with top and bottom plates. Pegasus and Paeco both sell these versions and the price is a reasonable $35-$40.
Terry

This thread was discussed between 18/07/2003 and 24/07/2003

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