How to Modify your Weber Carburetor properly OR
Weber Carburetor Porn!!!! OR
How to turn your expensive Italian/Spanish engine bit into an undriveable piece of crap . . . . Part three . . . . (yes, this will be a multi-step tutorial . . . .)Although these modifications will be specifically for Weber Carbs,
the concepts behind the ideas will work for most throttle shaft carburetors that utilize fixed venturies ("chokes")and fixed boosters ("aux venturies").I shouldn't have to say this, BUT, if your carb is not clean and in PERFECT working order, deal with that beforehand. Buy a rebuild/tuning manual SPECIFICALLY for your carb, as I am not going to cover basic rebuilding/installation/synchronization/vacuum leaks/linkage. LOTS of time is wasted trying to tune Weber carbs that need to be rebuilt. DO NOT waste your time on an old, used Weber! Just clean and rebuild it first. Replace any/all worn and/or questionable parts. If you can't tell if the part needs to be replaced, you should not be rebuilding the carb! Take/send the carb to a Weber specialist, it's cheaper in the long run.Before starting, a disclaimer:
Carb modification, especially Weber carb modification, should not be undertaken lightly. Weber parts are expensive, often difficult to obtain, AND, easily turned into junk by the enthusiastic, unwary, would be tuner. The best method is to amass a large pile of GENUINE Weber parts to start with, AND, have access to a flow bench LARGE ENOUGH TO FLOW CARBURETORS, to verify your work/"improvements". Caveat emptor. So Ya Wanna "Fix/Improve" Your Weber Carburetor?What you need to get started.Below are a couple of photos of a flowbench adaptor I constructed to flow Weber carbs, one side at a time. This particular adaptor is designed for Weber DCOE/DCO side drafts. You will need to adapt to your carb in a similar fashion. This adaptor is constructed from MDF (medium density fiberboard) and sealed with 2 coats of polyurethane varnish. Before anybody comments about wood Vs. metal adaptors, you need to realize that your Superflow flowbench is made from plywood, covered with laminate material and sealed with silicone caulk. Effective, non-leaking adaptors can be made out of various substances, say beryllium or platinum if you have enough time and cash. Wood/plywood/MDF works great, is easy to shape and doesn't leak when sealed. You just need to check for leakage after you fabricate them and resolve any leaks you find. This adaptor had zero leakage.
6.5"/7" squares provide enough material for the S/flow 5" square bolt pattern extra height provides room for throttle lever actuation & better simulates a manifold.
The mounting studs are drilled & tapped into the MDF and sealed. This adaptor has a 45mm "manifold" opening to match the throttle plates of this size carb. You need a flow bench that will draw approximately 300 cfm @ 28" inches of water for 45 Webers, one side at a time. Flowing one side at a time doubles the flowbench time to flow a 2 barrel carb, but you can be aware of any differences in flow, from one side to the other . . . . . . and take the time to find out why and correct the problem.
Flowing both barrels together or larger carbs requires a flowbench with a higher flow capability. Flowing 4 barrel carbs requires a REALLY big bench, AND, they still test at reduced pressures.
That's enough to get you started. Put on your thinking caps and start makin' chips . . . . . .
Fordboy
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