View single post by Mark Rosenbaum
 Posted: 03-14-2005 04:36 pm
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Mark Rosenbaum



Joined: 03-12-2005
Location: Kingman, Arizona USA
Posts: 532
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 In my younger days, shade trees were generally in short supply and much of my Brit car repairing was done in ditches, culverts, or the occasional grassy meadow.  I once had the fairly memorable experience of replacing a rear axle outer seal while being closely observed by a large and somewhat aggressive cow....

For troubleshooting on Stromberg-fed cars, all the vacuum lines can be capped, giving you a classical basic gasoline engine whose various systems have few if any unexpected interactions.

If the vacuum retard mechanism is not working, there's no point to running a vacuum line down to it, and the line can be removed.  This leaves an open port on a tee, which you'd need to cap.  Alternately, the tee and its lines can be removed and replaced with a single hose from intake manifold port to vacuum switch (the tower-like gadget added to the rear carb).

I do recommend leaving the vacuum switch and its associated plumbing in place and functional.  This is notionally an emissions system but it also aids in maintaining the correct thin layer of fuel on the inside walls of the intake runners.  If you do remove it, then neither the vacuum port in the center of the intake manifold, nor the throttle bypass valve on each carburetor, is necessary; the former can be plugged, the latter ignored or replaced with  blockoff plates.

You may also wish to leave the carbon cannister and its plumbing in place.  This is one of the few early emissions systems that not only (a) works more or less as advertised but (b) does not hinder performance.  However, the cannister and its lines can all be removed without harming anything.  In the event you do remove things, you'd need to cap the metal line running back to the fuel tank.  I would then also recommend replacing the spigot on the manifold flange of each carb with a small brass pipe plug, rather than using a rubber cap which will eventually crack and leak.  IIRC, these have a standard 1/8" pipe thread.

As a reminder, the brake booster is also vacuum operated, and failures there may cause apparent carburetion problems.