Holley Carburetor

[Mark]

I have a holley carb on the A2, when setting still, I'll floor the foot feed, I'll see black smoke from muffler, which I am assuming it's the accelerator pump shooting the stream of gas to the carb.When I increase the rpms by just pushing the foot feed, no black smoke.When looked at the plugs, they were black(too rich a mixture)so the only reason why I figure is the main jets in the carburetor are too big/worn is why.Now this excess gas in the cylinders will promote ring wear as the gas washes away the oil?
Or could the accelerator diagram have a hole in it so it sucks too much gas?The mixture screw is what ever setting the TM says.
So maybe I should go back the the zenith carburetor?Any feedback for me?The mutt runs good, gas mileage is 12--15MPG which would eliminate the hole in any diagram.

[rickf]

Well, the Holley has an accelerator pomp with a piston, no diaphragm. So that eliminates that hole in the diaphragm. And if there was a hole the result would be no acceleration when you stomp the gas, it would just bog. There is no vacuum operating on the gas side of the pump. As far as the plugs a lot depends on when you read the plugs. To get a true reading on how it is running down the road you have to run 50-55 mph down the road and then dump it in neutral and shut it off and coast to a stop and pull the plugs right then and there. That is the only true way to see what is happening going down the road. These engines are low compression engines so they tend to run all over the place and the fact that you only had two dirty plugs tells me either it was idling for a while and they were probably the center two plugs or you may need a valve adjustment. Or you may have just caught it at a point between rich and lean as you were driving. The Holley was at least 17 years old and obsolete when the first A2 came out. You cannot get any parts for them besides a couple gaskets. I don't even work on them anymore unless someone sends a kit with it. And main jets don't wear out, if anything it would be running lean from the alcohol in the gas.

[Mark]

Thanks a lot Rickf, I'll do what you said to do, there was no alcohol in the gas, I can still get alcohol free gas here, gotta pay more for it.

[Egorto]

If you have the vapor recovery system on your A2, with the stock fuel pump and a Holley carb then try this. Get a Holley fuel pressure regulator with the fuel dump port on the bottom. Put it in-line between the fuel pump and the carb. The fuel dump port gets connected to the fuel return line to the gas tank that the zenith would have been ported to. The other small diameter port on the Holley goes to the air cleaner. You’ll need to change a brass fitting on the air cleaner to a three way. There is a diagram in the tech manual. The fuel pressure regulator needs to be set at 4.5 psi for the Holley. There is a port on the side of the regulator for a gage. This should solve your fuel problems. The Holley runs like a champ after you modify the fuel pressure and fuel return.

[Egorto]

If you have the vapor recovery system on your A2, with the stock fuel pump and a Holley carb then try this. Get a Holley fuel pressure regulator with the fuel dump port on the bottom. Put it in-line between the fuel pump and the carb. The fuel dump port gets connected to the fuel return line to the gas tank that the zenith would have been ported to. The other small diameter port on the Holley goes to the air cleaner. You’ll need to change a brass fitting on the air cleaner to a three way. There is a diagram in the tech manual. The fuel pressure regulator needs to be set at 4.5 psi for the Holley. There is a port on the side of the regulator for a gage. This should solve your fuel problems. The Holley runs like a champ after you modify the fuel pressure and fuel return.

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[Mark]

Thanks for the feedback, I'll do asap

[rickf]

The stock fuel pump should only be putting out no more than 4 1/2 lbs. of pressure as it is. Those regulators require a differential of at least 7-10 lbs. to get a reduction of pressure so I am not so sure and reduction you see is coming from the regulator. More likely it is coming from that rather interesting filter? The Holley should have no problems at all with the pressure coming from the stock pump. Mark, have you checked the fuel pressure before throwing parts at it?

[Egorto]

My fuel pump was putting out 7psi prior to the filter and regulator install. The Perko fuel filter doesn’t cause a measurable fuel pressure drop. The regulators are cheap and and easy fix. Good way to tell if your fuel pressure is too high for your Holley is take the air intake off and look with a flashlight in the carb barrel. You’ll see fuel coming from ports inside that it should not be.

[rickf]

It sounds like someone replaced the original spring in the fuel pump with one that was stronger. These pumps never put out 7 lbs. stock, not even close.

[Egorto]

Positive displacement diaphragm operated fuel pump with an internal relief valve. With the zenith there was a fuel overflow port which allowed excess fuel to return to the tank. The Holley did not have the fuel return. Once the carb bowl got full and the fill valve shut there was no where for the excess fuel to go. Over pressurizing the Holley to the relief pressure setting of the fuel pump internal relief. The in line regulator dumps excess fuel to the tank and prevents over pressurizing the Holley. It works as installed.

[rickf]

You are wrong, This is NOT a positive displacement fuel pump. This is a spring operated fuel pump and the pressure is set by the strength of the spring pushing down on the diaphragm. The cam operates the diaphragm to pull fuel from the tank, the spring operates it to push fuel to the carb. When the float closes in the carb the spring will exert NO MORE then the preset value on the diaphragm until the float opens that valve and allows more fuel into the carb. This is how carburetors have worked for 70 years and nothing has changed. There is no such thing as a pressure fuel return on a carburetor. What you are referring to as a "Fuel" return is actually a vapor relief orifice to allow fuel vapor to return to the tank in the event of a vapor lock. Have you ever looked at the size of the orifice in the A2 return? You are not getting much gas through there! The only vehicles that have a pressurized fuel return are fuel injected and diesels. I have been doing this for 50 years and when I had my shop I specialized in carburetors and electrical.

[Egorto]

Yup, and it works perfectly as installed. You can see the pics.

[Mark]

No I haven't checked the fuel pump pressure, not lately anyway, a long time ago I did, it will take some digging to find it, will do asap.FYI , the A2 has been backfiring after letting up on the gas, so I figured the coil is going out so I drove it til it did..... 5 blocks from my house, just a couple of hours ago.LOL.
Thanks for the feedback

[Egorto]

Here is a bruise for that ego

http://militarynewbie.com/wp-content/up ... OD1620.pdf

[rickf]

Nice of you to send the supporting document. I suggest YOU read it! As far as my ego, it is safe and secure and NOT part of my username. I strongly suggest you go to that document and go to lesson 1 Task 2, Page 12 Part C, That is the section for mechanical fuel pumps. Especially concentrate on subsection #7 which explains the function of the cam and diaphragm spring on fuel pressure and how it will not move any fuel UNTIL the pressure drops.
I strongly suggest that before you go throwing out false and misleading information you actually read up on the subject yourself.
And if you want to make any more snarky comments to me do it by PM.