I've been having an intermittent issue with missfiring and one time an absolute lack of power. Most of my ignition system was 10 years old and I did find some issues there and have corrected them. Hoped that was it. While checking timing after the install of the ignition stuff it would not idle well but it did eventually clear up. The real short test drive went well and when I got to my driveway it was idling poorly again.
It seems to rev and hold higher rpm well well but won't idle well in the garage, no load. It will stall unless I give it some throttle once in a while and is difficult to start if it does stall like it is flooding So I pulled the aircleaner and looked down the venturis and found fuel coming from the passenger side primary booster, with the throttle closed, in the idle position. Further, I turned the idle adjustment screws all the way in and it kept running. So my thought is bad power valve or gasket or bad needle/seat assembly, or a sunken float. I then unscrewed the sight plug and fuel poored out like a miniature fire hose for about half a second, seeming to support the bad float or needle idea.
Then I though "what about fuel pressure." The pump is electric. I checked that and 12psi is indicated on the gauge, the maximum of my regulator. I tried another gauge and still 12psi so no issue with the gauge. The problem there is that the fuel pump is rated for a 7-9psi but when I installed it, the most I could get was about 5psi so I'm confused about this 12psi indication. If I just let the pump run with the engine off, no fuel overflows anywhere,as if the needle seat, and float is working properly.
The carburetor is a Holley 570 Street Avenger, center hung float bowls. I did remove the needle and seat assembly. The o-ring looks grey and powder like on the outside, where it contacts the bore of the needle/seat cavity of the float bowl. It looks like it may be cracked part of the way around the perimeter but it could also be a molding line from the original manufacturing of the o-ring as I don't know what these should look like when brand new. The needle itself looks ok. I don't really know what to look for but it looks good to me. I can see where it contacts the seat but I don't think it looks significantly worn or anything like that. The carburetor is about 10 years old at this point about July of 2009 that it was installed.
I didn't dig any deeper because I don't understand how there can be 12psi of pressure if the pump is not capable of that. That must mean something.
Maybe if the pump was dead headed it could peak higher than it's rating? But, particularly, if the engine is getting flooded at idle, and seems to rev and hold higher rpm, it wouldn't have that issue, right?
It seems like it may no longer be intermittent. Hopefully it stays that way so I can get to the bottom of it.