Weber jet recommendation |
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Weber jet recommendation |
SKL1 |
Nov 22 2015, 09:32 PM
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#1
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Senior Member Group: Members Posts: 1,602 Joined: 19-February 11 From: north Scottsdale Member No.: 12,732 Region Association: Upper MidWest |
2.0 with Webcam and Mallory distributor. Timing set and carbs synched, but really flat just off idle. Runs better when further up in the revs.
At 1800' in AZ. Currently: 40 IDF, 200 air correction, F11 emulsion tube, 115 main, 58 idle, 55 float bowl, 28 venturis TIA... |
ThePaintedMan |
Nov 24 2015, 04:07 PM
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#2
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Advanced Member Group: Members Posts: 3,886 Joined: 6-September 11 From: St. Petersburg, FL Member No.: 13,527 Region Association: South East States |
OP - you did you due diligence with the fuel pressure, good to know. As Kevin mentioned, go ahead and check/confirm your timing (around 34 degrees @ 3400 RPM) and make sure you have a good valve adjustment on it. As was mentioned, float height plays a role here too, but hopefully you got that right when rebuilding the carbs.
Those 28mm venturis are a good size for that engine and a good place to start. You might get a little more top end out of it later with 30mm chokes, but it's going to mean retuning the idles and mains and probably best done on a dyno. For the time being, I would go with the specs that 72Hardtop suggested. As you are at altitude, you're dealing with a less dense charge which will require less fuel. 58 idles does indeed sound big. 50 idles should do the trick, and go ahead and bump the mains up. Down here at sea level, 130s were right in the ballpark, so maybe you could split the difference at 125. Running a little rich won't be a bad thing. There is a guy on Ebay, Alfa1750 who sells quality Weber stuff from Italy. I've dealt with him before and he has been prompt and gotten my order right each time. You could also try buying used jets from somewhere like TheSamba, but keep in mind that a lot of people like to drill them and you may never know exactly what size you're getting without a jet guage. Darren, have you checked the sync on the carbs? What you're suggesting sounds like a lean overrun, explained like this to me by Racer Chris himself: a lean condition means that ignition does not occur on one compression stroke, then the next time around the excess fuel ignites, causing the overrun (again, only as I understood it). While the 55 idles do sound a little big, you might have one bank, or even one cylinder leaned out too much. Check the sync on both carbs first, with all bypass screws closed. Verify that synch at both idle and at part-throttle. Then move to bringing up the "low" cylinders with the bypass screws. Finally, adjust mixture screws for lean best idle - some folks add an 1/8 turn to make sure they stay a tad bit rich as these engines tend to run best that way (again, just my understanding). If having any issues tuning out the mixture, or if you're more than 2 turns IN, than your idles are too big. |
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