There's a metal disc in the center, with a raised portion in the middle. The raised portion is where the pump arm contacts it. That side would be down against the arm. If it's not then that's your problem.

 

the spring also performs that function.

 

With the spring tightened down as much as it is there is still preload on the diaphragm arm. You can see the diaphragm arm is also angled upward.

 

Did you put a 50cc pump diaphragm in it? Anyway, looks like you went opposite on the pump arm. You're supposed to extend it to take the play out between the arm and the diaphragm. In other words the longer the bolt/spring the less slack there should be.

 

No it's a 30 cc pump diaphragm and if you compress the spring it is suppose to take tension off of diaphragm arm, if the spring was fully extended there would be a lot of tension on diaphragm arm,spring, and diaphragm.

 

 

Does anybody see anything wrong or does all look well? I am going to replace the green diaphragm with a regular black rubber one just to see what difference it will make on the accelerator arm spring tension. I run regular old fashion gas in my truck not non-ethanol.

 

You had it on the correct way. For the past 15 years I've run my 331 with three Holley 2 bbls on a mix of 91 octane conventional gas ( less than 5% ethanol) and E10 93 octane fuel, alternating between fillups. It sits for a month at a time between startups. Ain't touched those carbs but once about 12 years back to rejet after adding spacers under them. The rubber diaphragm will make no difference in the spring tension. I would replace the steel ball check valve with the rubber umbrella style valve though. The steel ball can get gummed up and stick, preventing the diaphragm chamber from refilling. Holley ditched the steel ball valve decades ago. That could be your problem if it's sticking

 

Thanks baddad457 for all your input, I called the Holley tech line and they said it is not possible to change over from the ball check valve to the umbrella because of that metal bar that sits below the ball. I took the float bowl off and sprayed the ball with carb cleaner and it doesn't seem to be gummed up at all. At this point I checked everything out and everything seems to be in good operational order as far as the carb goes and even the green diaphragm on the bottom of the float bowl is supposed to be a premium diaphragm and the Holley tech recommends I keep it. So I am going to put he carb back together and back on the truck. The hesitation has got to be in my tuning maybe timing issue.

 

The Holley tech asked what my fuel pressure was and said the recommended pressure is around 6 psi. I need to get a adapter for my fuel line so I can check it, any recommendations? I will post a picture of my fuel line, I may replace the entire section around the black hoses, fuel filter, and connection to carb.

 

 

As having been advised previously, you need two additional fuel line clamps at the fuel filter or you may experience something no one ever wants to see...

In addition, after installing tubing headers and a low restriction exhaust system, the fuel calibration curve will be leaned so you have to compensate for that.

You also need to study that HOLLEY HP book you bought not only for ACCELERATOR PUMP ADJ but overall theory.

BTW- The carb is not too big. It may be/most likely calibrated for another application. The better way to go about it (IMO ... ), is to take the LIST NO. and find the original calibration and go from there.

OH! That gauge you bought is a combination VACUUM-FUEL PRESSURE GAUGE. You should be able to attach it to the fuel filter outlet nipple (after adding two fuel line clamps) to get base fuel pressure. You would then need a TEE to check pressure and delivery at all RPM's.

 

Been a long time but I was under the impression all you needed to do was remove the thin metal bar and ball bearing and install the umbrella. If not You could also replace the bowl with a newer bowl with the umbrella valve.

 

In case you haven't already checked, the accelerator pump pushes the fuel through this tiny passage in the pump chamber that has to pass through a tiny hole in the metering block, through a tiny hole in the gasket between the block and the carb body. If the gasket, block, and body aren't aligned properly, the flow will be obstructed. You can check this by looking at the impressions on the gasket after you take it apart. I've always felt that the Holley castings seemed a little coarse, and sometimes they just don't want to line up.

Due to problems I was having in other parts of my fuel system at some points in the past, I was having to take one of my carbs apart every week. I noticed that the Holley gaskets were designed to stick to the metal parts, and each time I took them apart, I would destroy them, and had to clean off entrails from the carb. I ended up getting some re-usable neoprene rubber gaskets made by Moroso. They're 3X the cost of Holley's but they're well worth the price when you're tuning your carb. Just not having to scrap off remnants from the carb parts each time saved a lot of time and effort.



The last time I had to get into one of my carbs, I had to replace the accelerator diaphragm because it had stiffened up, and was responding too slowly, causing stumbling during tip-in. It was one of the standard black versions that I estimate had been in there for about 8 years. I replaced it with a similar model as it's what I had lying around. If I had to do it again, I would try the fancy green one to see if it lasts longer.

 

Not an authority, seem to recall fuel cross over tubes are different lengths depending upon type of fuel metering bowl? Do not believe one can not mix and match bowls, either umbrella or check ball and I believe depending upon type determines length of the cross over tube?