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#1
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need help with a Holley carb...
Hello,
I have what I "think" is a lean surge going down the road at steady speeds. When driving at about 40-45 mph steady throttle it feels like the car is slightly surging. The rpm at that speed is about 2000-2100 rpm and am not sure if the torque converter could be causing the surge. I've never had automatics, only manual transmission cars in the past so it's all new to me. The car has an Edelbrock Performer RPM manifold with an older Holley 780 cfm dual feed. The Holley is a 3310-1, which is the older version of the new 3310 750's. The float levels appear correct, with the car at idle you can see fuel at the bottom of the clear plugs. The idle mixture screws are turned out 1.5 turns. The car idles in gear at 750 rpm. The torque converter is of unknown origin. It stalls at about 2000 rpm (if I power brake the tires spin when I get to 2000 rpm). Could the torque converter not be fully "locked up?" If I give it gas the surge goes away, and it doesn't seem to do it when going steady at 65-70 mph (3200 rpm). Any idea's would be appreciated, Mopar_Maniac |
#2
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It could be a lean surge, try backing the mixture screws out a half turn at a time to see if the surge goes away.
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#3
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John...
Thanks for the reply. I'll give it a shot later today and see if it helps. Mopar_Maniac |
#4
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It is difficult to say if you are still running off the idle circuit at 2000 rpm. Maybe you need to jet up the primaries 1 or 2 sizes. Do the idle mixture adjustment first just to see.
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#5
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I still have not taken my car out since writing about my problem. I'm hoping to get a chance later in the week.
I turned the mixture screws out to a total of 2 turns out. After I drive it this week I'll post the results. Thanks, Mopar_Maniac |
#6
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Are you running a vacuum advance on the distributor? A little too much vacuum advance can cause a surging like you have described when the total advance (without vacuum) is set in the 34-36 degree range.
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#7
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beep...
I have the Mopar Performance distributor with orange box. I have the timing set at 35 degrees total (not including vacuum) and it's all in by 2000 rpm. I do have the vacuum advance hooked up. I don't have a vacuum tool to check how much vacuum the advance is putting in, or when it comes in. I didn't really think I needed to worry about it cuz it doesn't ping. If the carb adjustment won't fix it, I'll try disconnecting the vacuum advance. Thanks, Mopar_Maniac |
#8
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It won't necessarily ping while cruising when this condition exists. And, as you know, as soon as you hit the throttle the vacuum-assisted advance goes away. The main symptom of this condition is the slight bucking/surging (in a stick shift car it may not as "slight"!) while trying to maintain a steady speed at the lower rpm's. It is real easy to test this, just pull off the hose at the canister and block it off with a screw or something (so the carb won't have an excuse to lean out!) and give it a drive. If that fixes it or most/some of it you can adjust the canister with an allen wrench through the vacuum line fitting, I can't remember which way to turn it right now though, sorry!
If you still can't get it adjusted down enough but you want it to look like it is hooked up then you can put a vacuum cap over the fitting on the canister then push the hose on over that. There will be no vacuum advance but it will look stock. Be careful not to tear the little cap or the vacuum will get through anyway. (As a Mopar_Maniac like me you may know all this already, so please excuse me. I have put the detail in here for those that may be reading this topic to gather info) Good luck, sounds like a fun ride!!!! |
#9
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beep...
I did know about the adjustable vacuum can, but thanks anyway. It's alway's nice to have others confirm things for you. I try to always make one change at a time to check the results...that way I know what fixed the problem. I'll post after checking it out later this week and let you guys know if, and what fixed it. Thanks again, Mopar_Maniac |
#10
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Right on.....
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