psears

Hello,

I've a Motormeister-built 3.1L SC motor w/their Weber 40IDA-3C set-up and I have some problems. First, the car constantly runs rich, with the tell-tale sooty exhaust tip, and plugs that are sooty as well. My mechanic says that changing the idle mixture can't fix that problem, and the only way to change the overall mixture is to change the main jets. Is this true? If so, what jets would y'all recommend? The valves, timing, ignition, and new factory wires have all been checked/adjusted.
Secondly, The Webers seem to be leaking excess gas not only onto my freshly-painted manifolds, but into the oil as well!?! My mechanic had to change my oil (which had only around 1500 miles on it.) When looking at the carbs, there appears to be gas drops leaking out from the throttle-rod bushing end on one of them, while on the other bank the throttle rod appears to vibrate slightly in its body. While I realize that Weber no longer makes NEW carbs, I would have thought the people who sold me these would have rebuilt them properly-or am I off base?

Thanks!

Tom F

First, are your Webers "Made in Italy?" The US made (by Rochester, or Holley, or someone like that) ones are really poor quality. You'll be better off with a new set of PMOs or a properly rebuilt set of the old Italian Webers. Second, you don't say anything about checking your float level. In my experience, this is crucial on these carbs (well, on all carbs, really) and the rebuild parts (needle valves) that are around these days seem to be poor fits, making float level even more crucial. What you describe sounds like something other than a jet size problem, though you may have that, too.

Steve Weiner-Rennsport Systems

PSears:

First off, Tom is right on; the non-Italian carbs were really horrible, but no matter which ones you have, they must be in good condition and setup properly. I'd have the Haynes Weber Book handy.

Sooty pipes are no reliable indicator of rich running; the MTBE (and other things) in unleaded gas generate lots of carbon. You must either do some good accurate plug cuts or get a 4-gas analyzer to see what going on.

The first thing you should do is a thorough carb setup. This involves make sure that you have exactly 3.5 psi of fuel pressure and then setting the float levels at that pressure. You must also have a high-quality fuel filter such as the Racor #110.

With that taken care of, you can now perform the rest of the setup. This is what you should do:

1) Check and adjust accelerator pump outputs as needed. You need that little vial for that.

2) Check the condition of the throttle shaft bushings. If the shafts/bushings are worn, the engine will never idle or run right at low speed, and the carbs should be either rebuilt with new oversized shafts or replaced with PMO's.

3) Perform the air volume equalizations and idle mixture adjustments on each cylinder. You will need the Syncrometer for that.

4) After that its jetting time, assuming that MM installed jets close to what you actully need. This is where you must do plug cuts or use a load-type chassis dyno.

Idle jets, main jets, emulsion tubes and air corrector jets all must match your engine's configuration and you need to know its true displacement, compression ratio and camshaft profile to get it close.

Hope this helps, good luck!!!