Holley carb - Float bowl adjustment
I bought a new Holley 670 about 5 months ago. From the day I put it on the secondary float bowl would fill up to the very top of the sight plug (yes I adjusted the float). I changed the needle/seats and float. The original secondary float was the nitrowhatever type, I changed to a brass for the hell of it. I have taken it apart numerous times to inspect for grit , dirt or any abnormalities but found nothing that caught my eye. If I drain the bowl and set the float to its lowest point the fuel will stay well bellow the sight plug. As soon as I start to adjust it so I can begin to see fuel at the bottom of the sight plug the bowl will fill up to the top again.
Any attempts to lower the fuel level after it has filled the bowl results in nothing
Primary bowel has no problems and stays right at the bottom of the plug
FYI - When I originally put it on I used a stock mechanical pump (5-6 psi), I have since installed an electric pump set about the same psi
Any thoughts would be helpful
Change the needle and seat again. It took 4 needle and seat sets to finally get one that worked. See if you can find an old one offa known good carb. Good luck.
What is your LIST # (eg 1850-1 stamped into the air horn / choke plate area) and what is the brand and part number of the kit or needle and seats that you have been supplied?
There are 2 different types of needle and seat assy's.
The original Holley type uses a seperate adjusting nut and screw, and some of the aftermarket replacements use a needle & seat with a slot cut into it to do the adjustment with and a much thicker lock-nut to secure it.
Holley Tech float adjustment instructions
I always like to start with a "dry" setting method, which will get you VERY close, followed by a "wet" sight plug inspection and minor adjustment.
Do you have a regulator and pressure guage that you are using with that electric pump, or are you assuming the pressure is "as advertised"?
well its a 670 VS street avenger, so I beleive it uses the smaller needle/seat...something like .097 (going off of memory here). I purchased both a new holley float and needle through Jegs .. I dont recall what the needle/seat part number was
the numbers on the airhorn are
"I always like to start with a "dry" setting method, which will get you VERY close, followed by a "wet" sight plug inspection and minor adjustment."
I do the same
yes, I have a regulator and a pressure guage inline
Try swapping the N&S from the front bowl that you know works properly to the rear bowl. This will let you know if the problem is in the N&S assembly or possibly the bowl itself. Also, make sure to put some lubricant on the o-ring so that it doesn't get cut when you install the N&S into the bowl.
Ill do that, I appreciate the suggestion
Get a real holley N&S. I hate the knock offs.
Look to see if you are running out of adjustment from the float tang bending.
Adjusting the secondary side while running...you will need to wait untill the eccess fuel is burnt off before the level will drop. If you don't have four corner idle then it never drop while at idling.
I'm using genuine holley N&S, floats
Took the carb off the car and removed the bowls. Switched the primary n&s to the secondary and vice versa (as BG Tech suggested). I then set the floats dry but I also took a good look at the brass float in the secondary and i didnt like how little adjustment I had (for lowering the fuel level). The brass floats dont have a tang to be bent so I switched back to the Nitrowhatever float and bent the tang up. this float was not the factory float but a new one I had
I also set the fuel pressure to 5psi apposed to the 6-7psi I had before.
I got the engine running and had to raise the primary float a bit, secondary looked good just at the bottom of the plug... then tuned it. By this time the secondary bowl filled to about mid way and the garage was full of eye burning exhaust from being to rich at start up.
If the same bowl is having a problem setting the float level with different floats, and N&S assemblies the hole through the bowl may be a touch over sized causing fuel to leak around the outside of the o-ring on the N&S assembly. If you have some extra o-rings you might have one that is a touch bigger and it would help otherwise you'll want to check with Holley.
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