Carb issue
Thread Starter
Joined: Dec 2008
Posts: 16
From: Texas
Carb issue
Hey guys new to the forum and introduced myself on the new members link.
I have an issue with my 750 holley carb. Cant get it to start.
The carb shoots gas out the blow vent when I try to start.
I tried tapping the carb to get the float to come down but still does it.
Do you guys have any other suggestions, is this a common problem? Thanks in advance!
I have an issue with my 750 holley carb. Cant get it to start.
The carb shoots gas out the blow vent when I try to start.
I tried tapping the carb to get the float to come down but still does it.
Do you guys have any other suggestions, is this a common problem? Thanks in advance!
4th Gear Member
Joined: Sep 2008
Posts: 1,839
From: Connecticut
Is gas shooting out of both vents or just one side? This could be high fuel pressure (shows up on both sets of barrels), crap caught under the seat (usually only one side), a stuck float, etc. Best bet is to try and adjust it if it is one bowl and if that doesn't work, take it apart. If it is both sides, check your fuel pressure.
5th Gear Member
Joined: Apr 2007
Posts: 2,100
From: Texas Hill Country
Good point about the trash and fuel pressure. I had my car go dead rich the other day and die from trash sticking the bowl valve until the old girl coughed up the hair ball. Not fun in rush hour traffic! High fuel pressure will cause the float to not be able to keep the gas out of the bowl thus blowing out the vent. Do you have an electric fuel pump or aftermarket high pressure pump? Do you have a pressure regulator?
Thread Starter
Joined: Dec 2008
Posts: 16
From: Texas
guys thanks for the reply. It shoots out one side. Its an electric pump. I do have a pressure regulator. Will have to check to see what psi it is. The motor is a 351w. I will use your suggestions and work on the car tomm. We are going through a cold front here (in the 30's) and sleet. Wish me luck!
5th Gear Member
Joined: Apr 2007
Posts: 2,100
From: Texas Hill Country
Install a permanent pressure gauge if you are running a pressure regulator. That way you can keep an eye on it because they do require adjustment from time to time.
Also keep in mind that a 750cfm carb is way big for a 351CID. You cannot generate enough air flow velocity, volumetric efficiency, or rpm to need that much carburetion. Because you are so over carbed, it is going to be very difficult to tune that carb for the correct AFR on that motor, and you will always have fuel atomization issues. I have a Holley double pumper 750 on my 383W and should have gone with a 700. It has taken a lot of trial and error to get things right.
Good luck and keep in mind that tuning this time of year in Texas is going to force you to tune again in a few months so it does not run rich during the summer months when we have less air per volume.
Also keep in mind that a 750cfm carb is way big for a 351CID. You cannot generate enough air flow velocity, volumetric efficiency, or rpm to need that much carburetion. Because you are so over carbed, it is going to be very difficult to tune that carb for the correct AFR on that motor, and you will always have fuel atomization issues. I have a Holley double pumper 750 on my 383W and should have gone with a 700. It has taken a lot of trial and error to get things right.
Good luck and keep in mind that tuning this time of year in Texas is going to force you to tune again in a few months so it does not run rich during the summer months when we have less air per volume.
