Fuel starve, or something |
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Fuel starve, or something |
arsprod |
Jul 26 2024, 02:56 PM
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#1
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Member Group: Members Posts: 210 Joined: 14-March 15 From: Indianapolis Member No.: 18,519 Region Association: Upper MidWest |
Teeners,
I swapped out the single carb that came with my 74 2.0 for new to me dual Weber 40's. It took a bit to get them jetted and adjusted but it's at least very close. The car runs great - and then it doesn't. With no consistency, it will start to stumble, cough, and backfire. Most of the time it works itself out though seems to be getting worse. I'm befuddled. (IMG:style_emoticons/default/confused24.gif) Here's what I know: - carbs are jetted main 145, air 200, idle 65, venturi 28 - plugs look ok, if anything rich - I don't seem to have any vacuum leaks - steady 3psi fuel pressure - timing and valves adjusted - new plugs Help! thanks Aaron |
Superhawk996 |
Jul 27 2024, 11:17 AM
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#2
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914 Guru Group: Members Posts: 6,469 Joined: 25-August 18 From: Woods of N. Idaho Member No.: 22,428 Region Association: Galt's Gulch |
Go smaller on idle (55) and maybe . . . Maybe . . . larger on main. Rule of thumb is main = 5x the Venturi. You’re already there. If it were me I’d just do the idle 1st.
Webers run off the idle about 70% of the time at light throttle, light load and 50-60 mph cruise. What you want is a seamless transition from the smaller idle circuit to the larger main (under acceleration and higher loads). Once it’s running consistently then I would run some high speed high load runs where I know I’ll be in the main 100% and then re-read the plugs to decide if I need to go bigger on the main. Post photo of plugs. To reiterate my 1st post . . . Randomness leads me to suspect ignition more than fuel. I ran a 009 back in the 80s for tens of thousands of miles and could never make it work properly, there were always holes especially when accelerating from lower engine speed. Eventually had to have it re-curved to make it work properly. But having said that it was always reliable and drivable. See post #12 to get an idea of how poor the 009 is vs ideal advance curve. http://www.914world.com/bbs2/index.php?sho...370919&st=0 |
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