ArdWrknTrk Posted March 27, 2019 Share Posted March 27, 2019 you said you screwed the idle air/fuel adjustment screws all the way in and it didn't make a difference. Houston, we do have a problem.... But in my experience if you turn the idle air/fuel screws all the way in on any carb that is working correctly the engine will die. That's because you **should have** just shut off all the fuel going into the engine. **unless the throttle is open far enough to uncover the transfers** Engine still runs with the idle mixture screws all the way in? Seems like the power valve is ruptured, stuck or the gasket is not seating. A vacuum leak will cause a high idle, but the engine needs to be getting fuel from somewhere. Link to comment Share on other sites More sharing options...
Gary Lewis Posted March 27, 2019 Share Posted March 27, 2019 you said you screwed the idle air/fuel adjustment screws all the way in and it didn't make a difference. Houston, we do have a problem.... But in my experience if you turn the idle air/fuel screws all the way in on any carb that is working correctly the engine will die. That's because you **should have** just shut off all the fuel going into the engine. **unless the throttle is open far enough to uncover the transfers** Engine still runs with the idle mixture screws all the way in? Seems like the power valve is ruptured, stuck or the gasket is not seating. A vacuum leak will cause a high idle, but the engine needs to be getting fuel from somewhere. Good upgrades, Jim. If the throttle is open past the transfer ports it'll pull fuel through them, even with the screws closed. And, I forgot it is a Holley, so could be getting fuel through a blown power valve or one w/a bad gasket. Thanks! Link to comment Share on other sites More sharing options...
jstone4646 Posted March 27, 2019 Author Share Posted March 27, 2019 you said you screwed the idle air/fuel adjustment screws all the way in and it didn't make a difference. Houston, we do have a problem.... But in my experience if you turn the idle air/fuel screws all the way in on any carb that is working correctly the engine will die. That's because you **should have** just shut off all the fuel going into the engine. **unless the throttle is open far enough to uncover the transfers** Engine still runs with the idle mixture screws all the way in? Seems like the power valve is ruptured, stuck or the gasket is not seating. A vacuum leak will cause a high idle, but the engine needs to be getting fuel from somewhere. Good upgrades, Jim. If the throttle is open past the transfer ports it'll pull fuel through them, even with the screws closed. And, I forgot it is a Holley, so could be getting fuel through a blown power valve or one w/a bad gasket. Thanks! The hose connections may be incorrect, I will double check that! Regarding the 1:35, Yes I was adjusting the vertical screw, which I thought was idle adjustment but clearly I need to read some more on the holley manual then and verify if I was or was not adjusting the right component (I count all my turns and return everything to its previous position after adjusting so its back to what it was before I messed with it. Regarding the air/fuel adjustment screws, yes....I ran them both all the way in and all the way out, and nothing motor running wise was affected. She just kept on chugging along with no studder, no shakes, no indication of struggle, just kept on running. We (son and I) actually picked up another truck last night, same motor, holley carb (different model carb)....my plan with that truck is to get her running, and flip for profit, but to also compare her engine compartment with the current project to see whats different in the vacuum system. The new purchase is a lot more equipped than my project truck....a lot more, but that is all conversation for another thread! I was turning this spring loaded screw here in the photo which I was fairly sure is the idle adjustment, need to double check. Link to comment Share on other sites More sharing options...
Gary Lewis Posted March 27, 2019 Share Posted March 27, 2019 The hose connections may be incorrect, I will double check that! Regarding the 1:35, Yes I was adjusting the vertical screw, which I thought was idle adjustment but clearly I need to read some more on the holley manual then and verify if I was or was not adjusting the right component (I count all my turns and return everything to its previous position after adjusting so its back to what it was before I messed with it. Regarding the air/fuel adjustment screws, yes....I ran them both all the way in and all the way out, and nothing motor running wise was affected. She just kept on chugging along with no studder, no shakes, no indication of struggle, just kept on running. We (son and I) actually picked up another truck last night, same motor, holley carb (different model carb)....my plan with that truck is to get her running, and flip for profit, but to also compare her engine compartment with the current project to see whats different in the vacuum system. The new purchase is a lot more equipped than my project truck....a lot more, but that is all conversation for another thread! I was turning this spring loaded screw here in the photo which I was fairly sure is the idle adjustment, need to double check. I think that is the correct screw for idle speed, but turning it in/clockwise should have raised the idle speed, not lowered it. So, I'm confused. On the other truck, if it is a factory 4bbl carb then it'll be a very different one than you have. It'll be the 4180C, as discussed here: Fuel Systems/Carburetors, Chokes, & EFI/Holley 4180C. And, check it out but I'm very sure those hoses are wrong, and may be causing a problem. Having said that, there were some Holley-designed Motorcraft 2150 carbs that had an external connection to the power valve. But I'm pretty sure no recent Holley uses that. Link to comment Share on other sites More sharing options...
PetesPonies Posted March 28, 2019 Share Posted March 28, 2019 you said you screwed the idle air/fuel adjustment screws all the way in and it didn't make a difference. Houston, we do have a problem.... But in my experience if you turn the idle air/fuel screws all the way in on any carb that is working correctly the engine will die. That's because you **should have** just shut off all the fuel going into the engine. **unless the throttle is open far enough to uncover the transfers** Engine still runs with the idle mixture screws all the way in? Seems like the power valve is ruptured, stuck or the gasket is not seating. A vacuum leak will cause a high idle, but the engine needs to be getting fuel from somewhere. Well the way the fuel comes in when the idle screws are closed is through the nozzle. The vacuum leak draws enough air that the nozzles will trickle enough out to run.Also, the throttle plates sometimes need adjusting. When they are open too far, the transition slot is uncovered and can supply fuel as well. Link to comment Share on other sites More sharing options...
vjsimone Posted March 29, 2019 Share Posted March 29, 2019 "I tried adjusting only the idle screw 1/4 turns at a time in both directions and all I could get it to do was increase idle speed instead of lower. " So what was the idle rpm at its highest when you were doing this ? Do you have a Vacuum Gauge ? What model carb do you have ? Link to comment Share on other sites More sharing options...
vjsimone Posted March 31, 2019 Share Posted March 31, 2019 So this is where am I at now, I only had about 30 minutes to give it a once over, but I think I covered all the bases of the vacuum system...what little of it there is. Please educate me if there are components I am missing, and keep in mind since I do not have heat or A/C in the truck, I am sure there are several bits missing on that end which are just plugged now. If you have done this; “"I came over here to the idle adjuster" and then you said you turned it clockwise all the way in. “ I suggest at some point, after you plug the vacuum ports as Gary suggested, that you turn your curb idle screw out to the point that it just lifts off the throttle stop, this will close your throttle plates. Check to see that the choke system is not keeping the plates from closing all the way. Then bring the curb idle screw up to where it just touches the stop, + ¼ turn. This is a good starting point. Link to comment Share on other sites More sharing options...
jstone4646 Posted March 31, 2019 Author Share Posted March 31, 2019 If you have done this; “"I came over here to the idle adjuster" and then you said you turned it clockwise all the way in. “ I suggest at some point, after you plug the vacuum ports as Gary suggested, that you turn your curb idle screw out to the point that it just lifts off the throttle stop, this will close your throttle plates. Check to see that the choke system is not keeping the plates from closing all the way. Then bring the curb idle screw up to where it just touches the stop, + ¼ turn. This is a good starting point. I read up more on the electric choke, along with a visual inspection and found that my electric choke has a ground attached but there is not a 12v hot wire running to it...I assume this would cause an issue? Picture for reference Link to comment Share on other sites More sharing options...
Gary Lewis Posted March 31, 2019 Share Posted March 31, 2019 I read up more on the electric choke, along with a visual inspection and found that my electric choke has a ground attached but there is not a 12v hot wire running to it...I assume this would cause an issue? Picture for reference If the choke not working is an issue, then yes you'll have an issue. If your truck came equipped with a 351HO, meaning the Holley 4bbl carb, then it should have had a choke relay, as shown below. If so, then you are looking for the white/black wire. Link to comment Share on other sites More sharing options...
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