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MG MGB Technical - Weber down draft setup Instructions

Hey all
Just wondering if anyone may have the setup instructions for the weber down draft carb upgrade. I have one installed on my 77B and wanted to be sure the previous owner set everyting up right.Mostly on rerouting the air pump hoses and installing a PVC plug if neccessary.(mine dosent have one). Also if there is a part# for the KN air filter as mine does have a small hole in it and I cant seem to find a replacement.
Also how strong of a vacume does the dist advance need to operate correctly. The vacume off the weber is not very noticable.(could there be a leak?, a blockage?)Thanks
Dave Noe'
Dave Noe

Dave. A copy of the MGB installation instructions is contained in Pat Braden's book, "Weber Carburetors". They run five and one half pages--much more than can be covered here in a single posting.

If you have the original distributor, it went to manifold vacuum and should be hooked up to the intake manifold. So should the hose going to the brake booster. The front tappet cover, on my two cars, is hooked to the air filter to provide a source of minor vacuum for the PVC system. This set up works well and the cars pass the Arizona emissions testing set up in that manner.

Air filter. If you have a BAP imported auto parts store near you, they have filters available, both K&N and a similar, but less expensive, model. You need one with the plastic elbow in it to hook up to the line going to the front tappet cover. If there is no BAP, check for VW specialty stores as the Weber conversion is often used on VWs.

Do not remember, off the top of my head, how the air pump is hooked up except to the head air rails. If no one else answers, I will take a look tomorrow and see what I have. Les
Les Bengtson

Thanks Les
The brake booster is hooked up to the mainfold on the right side and on the left side its just plugged. I will tap into there for the Dist and cap off the one under the carb which doesnt seem to be very strong. My air pump is already removed and I would like to make it look "cleaner". I suppose I can get a thermostat houseing without the bracket and I can plug th holes in the head but I was wondering about the rest.( the canister behind the washer pump and the hose that runs to the front of the car,and what ever else there might be)
Dave Noe

Dave: go to http://www.racetep.com for detailed set up instructions, diagrams, and some excellent tech papers on Webers as well as replacement filters and other parts.
Terry

Terry that helps alot thanks
dave
Dave Noe

Dave, Have you put a vacuum guage on the engine to see just what it's pulling? I say this because the size of the vacuum hose you install will really affect the curve of the dist. on acceloration. Try using a TEE on the brake booster side first and orfice's to measure the inch's pulling to solve your problem. Vic
victor gardino

I will try that Vic
Do you know what the reading should be by any chance?
I was having a hard time finding the correct size fitting for the hole in the manifold. anyone know what this may be. I tried 3/8npt but this doesnt fit. but is very close.
Dave Noe

Dave, Try 3/8th's ips??? You should get a reading of around 20 to 22 inch's Hg at around 3000rpm. If it rises from about "0/2" to "20/22" (((idle to 3000))), you should have enough vacuum. Have you tried sucking on the vacuum hose when connected to the dist., cap off, to observe the base plate moving? If it moves your vacuum unit is probably ok. If it doesn't the rubber diaphram inside is probably cracked or ripped and needs to be replaced. Let's see what happens. Vic
victor gardino

This thread was discussed between 23/01/2004 and 28/01/2004

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