73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: McClainMoldenhauer on September 22, 2016, 08:55:33 pm
-
Ok, I just recently installed a Holley 670cfm carb on my 1979 454 suburban. I am having trouble with it dripping fuel through the boosters. Put a vac gauge on it and it's got about 6-8 in/hg at idle. I'm thinking I've got a vac leak but can't find one so if anybody has a vac diagram or any experience dealing with Holley carbs/emission systems any help would be greatly appreciated. Thanks in advance
-
Check the float levels and fuel pressure. Stock cam? How did you check for vacuum leaks? Have you verified ignition timing?
-
Check the float levels and fuel pressure. Stock cam? How did you check for vacuum leaks? Have you verified ignition timing?
Floats are good, pressure is at 4.5 psi. As far as I know, stock cam. Haven't checked for leaks because I can't keep it running. As far as timing, I pulled the original quadrajet to clean it up and the truck was running good. I'm thinking about just reinstalling the quadrajet at this point
-
Great idea! I have never liked Holleys. They leak like sieves! Unless you get an aftermarket carb like an AED, the stock castings can be really porous and all those gaskets below the fuel level just make for nightmares. Your Quadrajet has zero gaskets below the fuel level!
Guess what...I have a Holley 4150 on my '77 and it has been nothing but problems! I have a Shawn Murphy Quadrajet just waiting to go back on it!
-
I wholeheartedly agree that the QJ is difficult to beat, making it the best choice for any stock to mild performance build. Holleys can be downright temperamental and uncooperative - though when properly set up and matched to an application, they perform well. Essentially, every carburetor has its proper application and use, not-to-mention learning curve.
McClainMoldenhauer, there may be some fine debris caught under the fuel inlet needle(s) or the needles/floats may be binding. In addition, air bleeds could be plugged causing early tip-in. Check for free movement of the floats, check and clean the inlet needles, and spray the air bleeds with some carburetor cleaner followed with compressed air. DO NOT blow compressed air directly into the fuel bowls or you could damage the floats. Does your Holley have wet float level adjustments?
Once you get the engine running, spray carb cleaner around the carburetor base, along both sides of the intake manifold and around the various vacuum lines and fittings.
-
X2 on the float level. You could also have a piece of trash lodged between the needle and seat causing it no never shut off the fuel flow. I love holley's, and use them exclusively on my turbo cars. Like any other carb, they're great if you know how to tune them properly, there is a whole lot more to tuning a holley than a couple of air screws and main jets.