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MG MGB Technical - Just bought a Weber

Just received my Weber, Manifold and linkage that I bought on eBay recently for, what I think is, a good price.

Just got a few questions really
-Do you use the standard throttle and choke cable?
-How do they attach? I've only had a brief look but I'm not getting much sense out of the throttle linkage.
-What trumpets and air filter should I be looking at?
-Is there anything I need to change that I haven't got?

It will be bolted onto an engine which is +30, Ported & Polished head, 270 cam, Lightened flywheel and fully balanced.

(And yes I know it needs a good clean!)


K Goldup

What age of car is it going on? Is that the servo vacuum take off? What dizzy? Is there a vacuum take off on the carb if so is it up or down stream of the butterfly?
Allan Reeling

The stock throttle and choke cable should work. Mine did. The throttle cable feeds through the bracket and is held to the carb linkage by the stock locking screw. The choke cable has to loop around to the front of the carb to allow it to reach the starting jets. I was able to order one that feeds from the rear, but these are difficult to locate. Longflow and K+N make air filters that will fit it. I purchased a set of small trumpets, that fit inside the air filter, to reduce turbulence and aid in the atomization of the fuel. RAY
rjm RAY

Again, what age of car? From October 68 crankcase ventilation was from carb ports and not a PCV valve. If your car is later than this you will need to retro-fit a PCV or suffer the effects of internal condensation and corrosion.

The port on the upper branch looks big enough to be a servo takeoff to me, and should be a one-way valve or you will lose servo assistance if the engine stops spinning. Not that that makes a lot of difference unless you have the master with integral servo, when it is significant.

The distributor is irrelevant, all distributors work with both inlet manifold and carb vacuum.
PaulH Solihull

Its a '77 GT, 45D (I think?) distributor, For the crankcase breather can you just fit a filter like the small K&N ones on eBay?
K Goldup

The K&N filter only allows equalisation of pressures through a filtered orifice, which is exactly what the oil filler cap is doing anyway. For correct crankcase ventilation you need manifold suction on the crankcase from a PCV valve, in conjunction with the standard oil filler cap.
PaulH Solihull

Can someone explain to me why you would want to change to a Weber carb, when in theory you would not see any benefit below about 4000rpm and may indeed loose some torque up to that level.
Graham
G Cherry

For 5 years I was constantly playing with my SU's. Rebuilt them and was always playing with them. I am fair with a wrench so I feel confident in my work. I got tired, put on a 32/36 Weber, set it up and in 10 years and over 80K I have not had to play with it more than the traditional spring tune-up. I also have a Mallory Unilite distributer which I put on at the same time and I only check timing once a year and it has yet to be off. They might not be traditional but they allow me to spend more time driving and less time getting dirty. That is why someone would install a Weber. Ed
E kulick

Ed.
Perhaps the problem was that you were constantly playing with them!

David
David Overington

Don't do it !!!!! Sorry guys, I had one on mine for a couple years and it was crap, no power under 3000 rpm and had to disconnet and block off the vacuum advance and advance the timing to get it to run sort of ok.
Have a look at previous threads about this, there plenty and they're not good.
Good luck.
Spoggy.

Dave ( spoggy )

My 79 is bored +30, w/270 Crane cam and also a DGV Weber. Webers like advanced timing. Mine is set at 17 B.T.D.C. @1500 RPM Runs great on regular 87 fuel.

cheers

Gary
gary hansen

"Perhaps the problem was that you were constantly playing with them!"

Exactly so. Set up correctly to begin with, no faults, and not fiddled about with afterwards SUs will keep their tune - I'm tempted to say indefinitely, in terms of classic use. American emissions regs required them to stay in spec for 50k, i.e. not even a 10-year tune-up for very many classics, let alone annual.
PaulH Solihull

The other immediate thought is; where did this weber come from? What is the current jetting? The engine sounds ideal, and with a long induction track and suitable cam, it may still give reasonable torque low down.Bear in mind what a weber might do that the SU MIGHT not. it may give a more instant initial pick up,( Because of accelerator fuel pumps) off idle. But an SU can do this if tuned. The only reason our racing boys go for webers is the almost countless number of jets , emulsion tubes etc to account for all situations and all states of engine tune. Unfortunately, at present there is no guarantee that your set up will run better than the SU set up.
J.M. Doust

This thread was discussed between 07/06/2011 and 17/06/2011

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