This is just an FYI tuning tip for all those running a Holley.
I just got my engine running and the upgraded tranny installed from last year's catastrophe. My engine has always idled rough and rich, fouling spark plugs way too fast. I finally decided to t/s and ultimately what I found was that the fuel pressure was too high. I had read that a Holley would work OK without a pressure regulator up to 7.5 psi, turns out not to be true (at least on a real street car that needs to be able to idle). The carb was a new out of the box Holley, so I didn't think it was likely the culprit although after taking it apart I did discover 2 gaskets on the power valve... it didn't solve my problem. After playing with the idle bleeds to no avail all day Saturday, I decided to investigate the fuel pressure today. I'm using a Carter mechanical pump with 1/2" line from the tank to the pump, and 3/8" from the pump to the filter and then to the carb. I measured 7.2 psi ahead of the fuel filter. I thought this was a little close to the limit, so I put a restrictor at the pump and knocked it down to 6.1 psi and the idle smoothed out and the plugs look good. I should have thought of this a long time ago. I missed a local Mustang show chasing my tail all day yesterday trying to set the idle screws and throttle stop.
I just got my engine running and the upgraded tranny installed from last year's catastrophe. My engine has always idled rough and rich, fouling spark plugs way too fast. I finally decided to t/s and ultimately what I found was that the fuel pressure was too high. I had read that a Holley would work OK without a pressure regulator up to 7.5 psi, turns out not to be true (at least on a real street car that needs to be able to idle). The carb was a new out of the box Holley, so I didn't think it was likely the culprit although after taking it apart I did discover 2 gaskets on the power valve... it didn't solve my problem. After playing with the idle bleeds to no avail all day Saturday, I decided to investigate the fuel pressure today. I'm using a Carter mechanical pump with 1/2" line from the tank to the pump, and 3/8" from the pump to the filter and then to the carb. I measured 7.2 psi ahead of the fuel filter. I thought this was a little close to the limit, so I put a restrictor at the pump and knocked it down to 6.1 psi and the idle smoothed out and the plugs look good. I should have thought of this a long time ago. I missed a local Mustang show chasing my tail all day yesterday trying to set the idle screws and throttle stop.