Holley Secondaries Not closing after WOT. |
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rnaquin
Newbie Joined: February-13-2009 Location: United States Status: Offline Points: 22 |
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Posted: July-08-2009 at 7:57pm |
Recently completed the rebuild/install of motor on boat.
Atttempting to follow breakin recommendations from previous posts. 4160 carb was rebuilt with new vacuum diaphram. Boat idles at 800 rpm. Attempts to back down off WOT runs, the boat won't idle below ~1800 RPMs. The secondaries are staying cracked open a bit. I shut the motor off, closed the secondaries, re-start and all is well until the next WOT. Please be patient, I'm NO mechanic. Is there way to properly adjust this. All the part numbers on the rebuild were correct/matching on the carb rebuild/cleaning and the boat runs pretty good except for this. I noticed on the passenger side of the carb, there is a connecting rod from the primary to the secondary shaft. This rod attaches to an elongated hole on the secondary shaft (see photo). I assume that this rod serves 2 purposes, 1 to prevent the secondaries from opening too soon and 2, to close the secondaries. I can rotate the shaft and open the secondaries slightly when sitting at idle position causing the increase in rpm. So is this rod used to close the secondaries, and can I just adjust the bend in the rod to force the secondaries closed? Or is there a "more better" way to tune/adjust? Thanks Rick |
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Luchog
Grand Poobah Joined: April-17-2007 Location: Argentina Status: Offline Points: 2135 |
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you need to adjust the air mix screws for each side of the carb. Possibly have them out some.
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rnaquin
Newbie Joined: February-13-2009 Location: United States Status: Offline Points: 22 |
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I'm confused. There are no air mix screws on the secondaries. If you are referring to the primary side air mix screws, how/why would that stop the secondaries from closing?
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GottaSki
Grand Poobah Joined: April-21-2005 Location: NE CT Status: Offline Points: 3333 |
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Perhaps I can help.
Yes, the rod is bent to force the secondaries closed fully. HOWEVER, these rarely unbend themselves. Most often the idle mix screws go unresponsive when the idle fuel orifice clogs. The user then upps the idle screw to get it to run at idle, but it is now running on the transition slots and sometimes the main venturies can drip while idling. This causes the secondary-closing rod to go slack, causing the symtom you describe. TO SUM UP, it could just be the rod, but could also be the primary metering block is still boogared up. |
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SNobsessed
Grand Poobah Joined: October-21-2007 Location: IA Status: Offline Points: 7102 |
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Rick - Tom has good advice, make sure your carb is properly adjusted.
I too had a high idle problem & bent the rod you are referrring to (called a closer rod). It slips out easily if you open the primaries a little. Google a Holley website & it will detail high idle problems; bending this rod is one fix. I left a small amount of clearance so it wouldn't bind under any circumstance. |
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rnaquin
Newbie Joined: February-13-2009 Location: United States Status: Offline Points: 22 |
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Thanks for the info. Now I understand the correlation between the air mix screws and the secondaries.
It's a little too late to fire it up in the driveway to test the air mix circuits, I'll look into that in the morning. I had just rebuilt/cleaned the carb and let the metering block soak over night in cleaner and blew out all passages with compressed air. I re-assembled the carb setting both air mix screws to exactly 1.5 turns out. When it was re-installed the boat started immediately, and I haven't futzed with the screws at all. I was able to see how far the idle set screw was tightened. I removed the throttle cable and backed out the idle set screw until it no longer touched the stop, 3/4 turn. after that I was just backing out the screw. So it doesn't seem to that the idle stop screw was overly tightened to compensate. Thanks again for the info. |
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Luchog
Grand Poobah Joined: April-17-2007 Location: Argentina Status: Offline Points: 2135 |
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You wont be able to reproduce this on the driveway, the engine needs some load on it, so a water test is the way to go.
Try opening them 1/4 of a turn each first and see what happens. you could try with another 1/4 then. Also... when you rebuilt the carb, did you check the secondaries shaft was in good shape? |
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Brktracer
Senior Member Joined: December-20-2007 Location: South Carolina Status: Offline Points: 387 |
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The linkage does help the secondaries close but you have a problem with corrosion also. Corrosion on the throttle shaft is causing the secondaries to stick. Pull the carb and spray a bunch of WD-40 on the shaft where it goes through the throttle body. Move it open and closed a few dozen times. With the primaries open, the secondaries should spring back by themselves.
I've had this same problem with other carbs before, even double pumpers. |
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