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MG MGA - Judson vacuum advance

I've got a "George Folchi" rebuilt Judson Supercharger that I'm starting to get organized for my MkII. I have all the parts, and have gone over the installation steps. The unit was rebuilt for a previous owner, and it only has a few hundred miles on it, so I'm pretty sure I can install it as is. One unresolved issue is how vacuum advance is handled for the Judson. The period instructions suggest that the vacuum advance is not used (set timing to 10 deg BTDC ??), but George's hand-written notes make reference to a vacuum advance correction:

"Use a T fitting to connect your vacuum advance line from the distributor, and take vacuum from the outlet manifold (brass plug). This is also where you should connect a boost gauge".

Anyone have any advice on this ? Or any other tips I should be aware of ?

Thanks
Chuck Mosher
Chuck Mosher

Chuck,
You may wish to post this question on the supercharging page.
mike parker

I took the vaccum from the back of the intake manifold to show both vaccum and boost, the vaccum for the dist. was taken from the side of the carb with an adapter to get the advance.Let me know if you need more information. I have a Judson Guage in the dash and it works great.
JEFF BECKER

Chuck. Mayhaps you should contact George? To my knowlege, there is no generally accepted term which refers to an "outlet manifold". The only "outlet manifold" I can think of is referred to, by most of us, as the exhaust manifold.

However, most of the vacuum advance system are either hooked up to the carbs or, in the later model MGBs, to the intake manifold.

Thus, the originator of the conversion would be the best one to tell you what he intended to mean.

Les
Les Bengtson

The outlet manifold is in reference to the pressure side manifold on the supercharger.

Jeff's experience is the same as mine. The oiler went to a brass barb on the vacuum side manifold, the gauge to the pressure side, and the distributor on mine went to the carb via an 1/8" copper tube plumbed to the carb with a compression fitting.
Kemper

there are two vacuum outlets available on the Judson /Holley setup.

The one for a vacuum gauge is in the middle of the top surface of the inlet manifold (flat aluminium casting next to the rocker cover)

There is also a vacuum outlet on the carb, just to the left of the fuel inlet. This is normally blanked off with a bolt, but there is a fitting available to connect a pipe for a vacuum take off here too. (this is what Jeff is talking about)

If you want to make a 7lb gauge without paying a fortune for it, mail me off board and I can give you some material to do this - I made mine up for about $50, it works well and has a judson face on the gauge.

For instructions on the Judson and the Carb, look to the links on the vwjudson site. http://vwjudsonregister.tripod.com/mga_instructions.htm If you click the link, John will mai you the carb instructions too.

You may want to get a distributor that has the right advance profile for the Judson. I had mine done by Aldon in the Uk. Also a good idea is a J&S Safeguard knock sensor.

If you have a heater fitted, it is easier to reverse the stay bar between the thermostat housing and the blower.

dominic clancy

Thanks, everyone for the tips.
The vacuum locations and connections are clear to me now. On to the next problem now ...

-Chuck
Chuck Mosher

This thread was discussed between 07/10/2005 and 09/10/2005

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This thread is from the archive. The Live MG MGA BBS is active now.