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1963 AP5

Weber 34 ADM carb conversion info

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Here is some info on the Weber 34 ADM carb as found on the XE/XF Falcon. This was a popular carb for retrofitting onto other vehicles but they are have a couple of little quirks that can  cause problems if you are not aware of them.

Firstly there is the 2 stage low speed jet solenoid. This was an emissions control system that allowed the engine to run with one jet size when cold (think it was a 70) and when the engine warmed up it switched to a smaller jet to reduce emissions (possibly a 55). Problem is they get old and the little diaphragm inside fails allowing fuel to flow from the primary low speed circuit through the failed solenoid and into the line that supplies vacuum to the system. this causes the engine to run super rich. But don't worry there is a solution. 

The products that solve the problem can be found here.

https://www.weberperformance.com.au/product_info.php?cPath=6_268&products_id=631

https://www.weberperformance.com.au/product_info.php?cPath=6_268&products_id=1345

This is a larger jet holder that deletes the solenoid and the appropriate jets to go with it. You will need to mess around with the jets to find the right one for your engine. I think I ended up with a 60 or 65 in mine.

Here is a picture of the system on the standard carb and another of the carb on my car with the system deleted.

You will note that all the vacuum ports except the vacuum advance are simply capped off because all the emissions control stuff is gone (EGR etc).

 

Vac line pic.jpg

20200710_110756.jpg

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Second trap is the one that catches most people out.

The vacuum port for the power valve is in an odd place on these carbs and some off the shelf adaptor plates will blank it off causing the engine to run on the power valve all the time and run very rich. The port is actually under the base plate and is not open to either of the carb barrels.

The common adaptor plate available for a Holden 6 is a redline product designed for a 23/36 weber and there are a few problems with it when using a 34 ADM. The first one is it too low and the accelerator pump lever hits the adaptor. Secondly the barrels on a Weber 34 will not align with the adaptor. I chose to make an additional spacer to adapt the carb to the adaptor. Yes I know it seems silly to make and adaptor for the adaptor but it worked and solved both problems. 

You need to drill a vacuum port for the power valve in the adaptor plate and this port needs to also be drilled all the way through the stock manifold. If this port is omitted, vacuum will not be supplied to the power valve or the accelerator pump boost diaphragm and the carb simply wont work properly.

If you look at the underside of the carb you will find the port (it might even be blocked with crud). The port is located between the primary and secondary bores and continues up through base and into a tube in the carb body. The tube also acts as a locating dowel and can sometimes become damaged and obstructed if the carb hasn't been assembled correctly at some stage in the past.

Useful info on this can be found here

http://www.mbs.id.au/tuning/Carburettors/Weber/34ADM.htm

I wish I had documented this part of the process better and taken photos but I will try to show this with pics from the internet. 

ADM_carb.jpg

Exploded carb.jpg

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This may be useful to you to as well it shows the correct jets for the carb in stock form and this is exactly what I run in my car. These carbs are getting old and often people have messed around with them, changed jets for a particular application or drilled the jets. You can get tools for measuring the jets to ensure the orifice is the correct size, they are cheap and a very good investment.

ADM carb jetting picture.jpg

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One more pic showing the other side of the carb. I have the throttle nudger blanked off on my carb, I think this is supposed to hold the throttle slightly open momentarily if the throttle is snapped shut suddenly to smooth things out. On some models it may also have been supplied vacuum as an idle up system for air con etc. The diaphragm can fail and cause a vacuum leak and most of the carb rebuild kits don't include this particular diaphragm. You don't need it so I just capped the rather large vacuum port.

Alt view.jpg

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After a little digging through files on my old laptop I found the overhaul instructions for the carb.

If all else fails we can always read the instructions.

Weber 34ADM - Gregorys - Page 11.jpg

Weber 34ADM - Gregorys - Page 12.jpg

Weber 34ADM - Gregorys - Page 13.jpg

Weber 34ADM - Gregorys - Page 14.jpg

Weber 34ADM - Gregorys - Page 15.jpg

Weber 34ADM - Gregorys - Page 16.jpg

Weber 34ADM - Gregorys - Page 17.jpg

Weber 34ADM - Gregorys - Page 18.jpg

Weber 34ADM - Gregorys - Page 19.jpg

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Great info there mate, this one needs to be pinned.

 

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