Holley 650 Issue
Thread Starter
Instructor
Joined: Mar 2020
Posts: 108
Likes: 8
From: Fort Lauderdale, FL
Holley 650 Issue
Hello All,
I am running a 650 Holley #4777-3 on my 350 SBC. The car sits a lot but always runs good. I only use Non Ethanol fuel. I started it yesterday and it was running rough and stumbling. I pulled the air filter off to see that it was dropping fuel into the secondary side while at idle. I assumed maybe the float needle was stuck and not closing so pulled the bowl off the secondary side and found it clean inside. I blew into the fuel inlet while lifting the float with my fingers and the air flow stopped so the needle appears to be seating. Any idea what else would cause this problem?
Thanks
I am running a 650 Holley #4777-3 on my 350 SBC. The car sits a lot but always runs good. I only use Non Ethanol fuel. I started it yesterday and it was running rough and stumbling. I pulled the air filter off to see that it was dropping fuel into the secondary side while at idle. I assumed maybe the float needle was stuck and not closing so pulled the bowl off the secondary side and found it clean inside. I blew into the fuel inlet while lifting the float with my fingers and the air flow stopped so the needle appears to be seating. Any idea what else would cause this problem?
Thanks
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,809
From: Cool Northern Michigan
Captng1,
I too have the Holley 4777.
I think there maybe a couple of things going on here.
You should have a fuel level sight plug on each bowl, primary & secondary.
With the car idling, remove the sight plug. Fuel should just barely dribble out.
Rock the car sideways to verify fuel is at the correct level.
Double pumpers may need an adjustment at the accelerator pump arm & linkage.
If the gap / clearance is too tight, fuel will drip into the venturi at idle. Too tight can also damage the accelerator pumps diaphragm.
It doesn't take much vibration to activate the pump and discharge nozzle.
Holley specs calls for a 0.015 clearance. But, that is too loose and may cause a bog on acceleration.
Some people set it at zero gap. But that can lead to the dribbles your carb is showing.
There is a happy medium of 0.05 - 0.08.
You will need two small wrenches for the acc arm and a feeler gauge. If you are unsure how to set the clearance, Summit Racing has a video of the process. The gap should be checked at W.O.T. also, to avoid over stretch of the diaphragm.
I too have the Holley 4777.
I think there maybe a couple of things going on here.
You should have a fuel level sight plug on each bowl, primary & secondary.
With the car idling, remove the sight plug. Fuel should just barely dribble out.
Rock the car sideways to verify fuel is at the correct level.
Double pumpers may need an adjustment at the accelerator pump arm & linkage.
If the gap / clearance is too tight, fuel will drip into the venturi at idle. Too tight can also damage the accelerator pumps diaphragm.
It doesn't take much vibration to activate the pump and discharge nozzle.
Holley specs calls for a 0.015 clearance. But, that is too loose and may cause a bog on acceleration.
Some people set it at zero gap. But that can lead to the dribbles your carb is showing.
There is a happy medium of 0.05 - 0.08.
You will need two small wrenches for the acc arm and a feeler gauge. If you are unsure how to set the clearance, Summit Racing has a video of the process. The gap should be checked at W.O.T. also, to avoid over stretch of the diaphragm.
Tech Contributor
Joined: Aug 1999
Posts: 14,370
Likes: 6,364
From: At my Bar drinking and wrenching in Lafayette Colorado
I pulled the air filter off to see that it was dropping fuel into the secondary side while at idle. I assumed maybe the float needle was stuck and not closing so pulled the bowl off the secondary side and found it clean inside. I blew into the fuel inlet while lifting the float with my fingers and the air flow stopped so the needle appears to be seating. Any idea what else would cause this problem?
Thanks
Thanks
Thread Starter
Instructor
Joined: Mar 2020
Posts: 108
Likes: 8
From: Fort Lauderdale, FL
HeadsU.P. and Lars,
Thanks for your replies. The last time I ran the car which was not long ago, it ran fine. I don't understand why the float level or accelerator pump adjustments would have changed for any reason, which is why I believe it this issue is a different problem. Your thoughts?
Thanks for your replies. The last time I ran the car which was not long ago, it ran fine. I don't understand why the float level or accelerator pump adjustments would have changed for any reason, which is why I believe it this issue is a different problem. Your thoughts?
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,809
From: Cool Northern Michigan
One thing that can change the acc pump arm linkage clearance is when a fuel bowl has been removed and reinstalled.
There is enough play in the four bolts to allow shifting of the bowl.
Holley recommends checking acc arm every time the bowls have been removed. ( I never do)
Normally I would question the actual fuel bowl float material. Sometimes the brass units will get a pin-hole that sinks the float or slightly submerges.
However, I see you incorporate Ethanol free, so float damage is rare.
In my opinion, you are wasting a lot of money buying that overpriced fuel unless it's the last full tank of the season and storage is long term.
The extra money you spent per gallon is more than any cheap gaskets or "O" rings that you MAY need to replace.
Most newer carbs / gaskets today can handle the newer fuels w/o issues.
Storage is the worst issue with Ethanol. Not daily / weekly use.
There is enough play in the four bolts to allow shifting of the bowl.
Holley recommends checking acc arm every time the bowls have been removed. ( I never do)
Normally I would question the actual fuel bowl float material. Sometimes the brass units will get a pin-hole that sinks the float or slightly submerges.
However, I see you incorporate Ethanol free, so float damage is rare.
In my opinion, you are wasting a lot of money buying that overpriced fuel unless it's the last full tank of the season and storage is long term.
The extra money you spent per gallon is more than any cheap gaskets or "O" rings that you MAY need to replace.
Most newer carbs / gaskets today can handle the newer fuels w/o issues.
Storage is the worst issue with Ethanol. Not daily / weekly use.
Thread Starter
Instructor
Joined: Mar 2020
Posts: 108
Likes: 8
From: Fort Lauderdale, FL
Thanks HeadU.P.
Since the engine started running bad the bowls had not been removed since it was running good. Nothing had changed other than it sat for a while (although I have never had this problem before). This car is not a daily driver or even a weekly driver. Thus why I use Non Ethanol fuel. Ethanol fuel is absolute crap! The bottom of my carb bowls are pitted from letting ethanol fuel sit in them too long! I also had to put a new fuel tank in the car from Ethanol fuel attracting moisture (water) from the air and rusting pinholes in the bottom of my fuel tank. It may be possible that the secondary air bleeders may be plugged from sitting or something like that because the needle on the float seems to be closing all of the way. I think that is the only other reason that could possibly cause the carb to be dropping fuel into the secondary at idle?
Since the engine started running bad the bowls had not been removed since it was running good. Nothing had changed other than it sat for a while (although I have never had this problem before). This car is not a daily driver or even a weekly driver. Thus why I use Non Ethanol fuel. Ethanol fuel is absolute crap! The bottom of my carb bowls are pitted from letting ethanol fuel sit in them too long! I also had to put a new fuel tank in the car from Ethanol fuel attracting moisture (water) from the air and rusting pinholes in the bottom of my fuel tank. It may be possible that the secondary air bleeders may be plugged from sitting or something like that because the needle on the float seems to be closing all of the way. I think that is the only other reason that could possibly cause the carb to be dropping fuel into the secondary at idle?
Tech Contributor
Joined: Aug 1999
Posts: 14,370
Likes: 6,364
From: At my Bar drinking and wrenching in Lafayette Colorado
...and why don't you just pull the bowl level plug and check the float level...? You could have done that in less time than making the post here. So is your level high or low..?
Ethanol fuels have nothing to do with your issue. I have ethanol pump gas in all my collector cars and they sit through the winter with no problems re-starting in the spring. Any type of gasoline can gum up or cause a deposit in the needle/seat. If the float level is high, you have lost fuel level control and it will cause fuel drip out of the nozzles. Just pull the bowl plug and check it. If the level is high, clean up the needle/seat and re-set the float level. This is normal maintenance.
Ethanol fuels have nothing to do with your issue. I have ethanol pump gas in all my collector cars and they sit through the winter with no problems re-starting in the spring. Any type of gasoline can gum up or cause a deposit in the needle/seat. If the float level is high, you have lost fuel level control and it will cause fuel drip out of the nozzles. Just pull the bowl plug and check it. If the level is high, clean up the needle/seat and re-set the float level. This is normal maintenance.
Thread Starter
Instructor
Joined: Mar 2020
Posts: 108
Likes: 8
From: Fort Lauderdale, FL
Thanks Lars,
I am well aware that Ethanol fuel has nothing to do with my problem. There is no Ethanol fuel in my car. When the car was last run, it ran fine. Now it does not. There is no reason for my float level to become high from the car sitting. It was obviously not high when I last ran the car..
I am well aware that Ethanol fuel has nothing to do with my problem. There is no Ethanol fuel in my car. When the car was last run, it ran fine. Now it does not. There is no reason for my float level to become high from the car sitting. It was obviously not high when I last ran the car..
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Drifting
Joined: Sep 2019
Posts: 1,355
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From: St. Louis
By your logic, there is no reason the car should be running poorly at all. If nothing changed, nothing is wrong. However something did change since the car is not running correctly now. So, first check the float level as recommended. If that is fine, start looking at other potential causes for fuel dripping into secondaries such as a metering block gasket has gone bad or a power valve diaphragm has cracked. These things can happen just due to aging. You are getting good advice here. You can act on that advice or if this is beyond your capabilities, you will have to get someone else to fix your car.
Tech Contributor
Joined: Aug 1999
Posts: 14,370
Likes: 6,364
From: At my Bar drinking and wrenching in Lafayette Colorado
Thread Starter
Instructor
Joined: Mar 2020
Posts: 108
Likes: 8
From: Fort Lauderdale, FL
Thanks RacerRik,
When replying to HeadsU.P. I mentioned nothing had changed when referring to the acc pump linkage which he mentioned can change when the bowls are removed. I had not removed the bowls and was saying nothing had changed in regards to the linkage. I agree with you 100% that obviously something has changed which is why the car is not running right. I am definitely more than capable of any type repairs that need done. I have the carb off the car right now. I will check the jets for dirt or debris, check the power valve, remove the floats and check the needle valves, change the gaskets, and reinstall the carb and check the float levels as recommended. Being that the power valve is on the primary side, if it is bad can it make fuel spill into the secondaries? Just curious.. I thank you and everyone here for their advice.
When replying to HeadsU.P. I mentioned nothing had changed when referring to the acc pump linkage which he mentioned can change when the bowls are removed. I had not removed the bowls and was saying nothing had changed in regards to the linkage. I agree with you 100% that obviously something has changed which is why the car is not running right. I am definitely more than capable of any type repairs that need done. I have the carb off the car right now. I will check the jets for dirt or debris, check the power valve, remove the floats and check the needle valves, change the gaskets, and reinstall the carb and check the float levels as recommended. Being that the power valve is on the primary side, if it is bad can it make fuel spill into the secondaries? Just curious.. I thank you and everyone here for their advice.
Thread Starter
Instructor
Joined: Mar 2020
Posts: 108
Likes: 8
From: Fort Lauderdale, FL
I'm sorry Lars. I will take your advice and check my float levels. I am not arguing...
Can you please explain to me how the float level changes without manually changing it yourself? I am no carburetor expert and just trying to understand. I thank you for your help...
Can you please explain to me how the float level changes without manually changing it yourself? I am no carburetor expert and just trying to understand. I thank you for your help...
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,809
From: Cool Northern Michigan
Captng1,
On your 4777 which is a Holley 4150, there is no connection between primary & secondary fuel bowls or other transitions.
As stated earlier, if a float is sinking which does occur regardless of material its made from, will hold the needle valve open.
Any crud in the fuel system from the tank sock to the carb filter can jamb the needle valve open a smidge also.
It doesn't take much. A little piece of rubber fuel line, rust, even crud from the underground tanks at the station can cause issues.
As far as the Ethanol storage, Lucas makes a product just for that. Anti-Ethanol fuel saver. Green plastic bottle, Walmart, $9.
Put a couple ounces in the tank. Of course, you will need to allow the product several minutes to reach the fuel bowls.
On your 4777 which is a Holley 4150, there is no connection between primary & secondary fuel bowls or other transitions.
As stated earlier, if a float is sinking which does occur regardless of material its made from, will hold the needle valve open.
Any crud in the fuel system from the tank sock to the carb filter can jamb the needle valve open a smidge also.
It doesn't take much. A little piece of rubber fuel line, rust, even crud from the underground tanks at the station can cause issues.
As far as the Ethanol storage, Lucas makes a product just for that. Anti-Ethanol fuel saver. Green plastic bottle, Walmart, $9.
Put a couple ounces in the tank. Of course, you will need to allow the product several minutes to reach the fuel bowls.
Safety Car
Joined: May 2001
Posts: 4,740
Likes: 1,639
From: Fairfax Virginia
I used to use the Holley sight plugs that allowed the fuel level to be seen through a clear plastic lens. Then Ethanol appeared, and the clear plugs be came "opaque" and then fell apart very quickly. I then decided to use the Holley provided holes to verify the float level.
Never park your car for the winter without putting some anti-Ethanol protection in the fuel. Pilot training taught me to never park anything with an empty fuel tank/s or it will get condensation inside the fuel tanks.
We are still very grateful for your time and help Lar's! You are truly an asset to this Corvette Forum and most of us appreciate what you have done here!
If the float adjustment never went out of wack, they would not have made it adjustable. That little float needle/seat assembly "cycles a lot" while the engine is running and each time it cycles it is wearing away at the settings and components.
Never park your car for the winter without putting some anti-Ethanol protection in the fuel. Pilot training taught me to never park anything with an empty fuel tank/s or it will get condensation inside the fuel tanks.
We are still very grateful for your time and help Lar's! You are truly an asset to this Corvette Forum and most of us appreciate what you have done here!
If the float adjustment never went out of wack, they would not have made it adjustable. That little float needle/seat assembly "cycles a lot" while the engine is running and each time it cycles it is wearing away at the settings and components.
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To answer the question about how it's possible for the float level to change when it ran fine earlier.....
The float could have absorbed fuel and be heavier now. Not uncommon. Or a brass one has a leak and has some fuel in it.
Normal "jostling" can change float adjustments over time. You might not have noticed it running richer last time you drove it. Depends on how close it was to "too high" previously.
Certainly some trash can be in air bleeds or jets...but that's not causing a float level issue...which you had.
Ck float condition and reset the level. As mentioned "it happens" and you could have checked and adjusted it in about 10 seconds without removing the bowl.
JIM
The float could have absorbed fuel and be heavier now. Not uncommon. Or a brass one has a leak and has some fuel in it.
Normal "jostling" can change float adjustments over time. You might not have noticed it running richer last time you drove it. Depends on how close it was to "too high" previously.
Certainly some trash can be in air bleeds or jets...but that's not causing a float level issue...which you had.
Ck float condition and reset the level. As mentioned "it happens" and you could have checked and adjusted it in about 10 seconds without removing the bowl.
JIM
Thread Starter
Instructor
Joined: Mar 2020
Posts: 108
Likes: 8
From: Fort Lauderdale, FL
7T9182,
I was just trying to understand how a float goes out of adjustment without actually manually changing it. Didnt make sense to me. I guess it happens on these carbs. I apologized to Lars and have taken his advice and will check the float level. I have to reinstall the carb to the engine first...
I was just trying to understand how a float goes out of adjustment without actually manually changing it. Didnt make sense to me. I guess it happens on these carbs. I apologized to Lars and have taken his advice and will check the float level. I have to reinstall the carb to the engine first...