How Long Does it Take the Gas to Evaporate Out of Your Holley Carb?

[patrickt]

Well, I don't know the exact answer to that question. But, I can tell you that the answer is "less than three months." I know this because three months ago was the last time I drove the Cobra, and I decided to check the bowls this last weekend. Both bowls were bone dry. I filled them up through the sight plug holes, as warm weather (I think) is just around the corner.

[1795]

Patrick,

It would be interesting, if you have the time, to take a look at fuel level in your carb every other week until you can get it back out on the road to get an idea on how quickly it evaporates. I never checked mine with the ERA. I will check with the race car when it is built, as there will be weeks in-between races.

[patrickt]

Originally Posted by 1795

Patrick,

It would be interesting, if you have the time, to take a look at fuel level in your carb every other week until you can get it back out on the road to get an idea on how quickly it evaporates. I never checked mine with the ERA. I will check with the race car when it is built, as there will be weeks in-between races.

Hmmm, I wonder how I would do that.... Probably the best way would be to take out one of the bottom screws from the bowl and catch all the fuel that comes out. Pour that in to a graduated cylinder, put the bolt back in and pour the gas back in to the vent. Then repeat. Of course, the really easy method would be to just get a mayonnaise jar, fill it up to about the height of a sight plug, punch a hole in the lid about as large as the vent tube, stick a short run of surgical tubing in there, then punch two more little bitty holes in the top to mimic the well and bleeds, and then just put it on your garage floor and watch it.

[A98Coupe]

Patrick,

Think yourself lucky. My dual quad QuickFuel custom carbs drain down into the engine within a few hours!

After spending most of last season stripping the carbs and replacing the gaskets I finally found the root cause - the main bodies are porous! Obviously poor quality castings from the far east...........

Now trying to sort the problem out with my engine builder but apparently Quickfuel were bought out by Holley a few years back and since then they have become unresponsive to supporting customer problems

[patrickt]

Originally Posted by A98Coupe

After spending most of last season stripping the carbs and replacing the gaskets I finally found the root cause - the main bodies are porous! Obviously poor quality castings from the far east...........

Yikes. I've never heard of porous main bodies. I do know that the dichromate has slowly dripped off my Holley, and "dripped" really isn't the right word, it seems more like a very, very fine powdery mist that just drops off from the bottom up. It actually leaves a stain on the manifold that looks like an oil stain, but that comes right off with a paper towel and soap. But my Holley is now over ten years old, so I guess it's too much to ask for the coating to stay on that long.

[blykins]

Check the power valve Patrick...

[Sydney]

I can't help you with a Holley, but I can tell you that my Edelbrock will be empty in 10 to 11 days pretty consistently. I have a Schrader valve just under the fuel filler neck that I use to put 1-2 psi air pressure to the fuel tank for a minute or so to fill the carb when I haven't driven for a while.

[RodKnock]

Originally Posted by patrickt

I filled them up through the sight plug holes, as warm weather (I think) is just around the corner.

Dumb question. Can't you remove the air cleaner and pour a small amount of gas thru the butterflies instead?

[patrickt]

Originally Posted by blykins

Check the power valve Patrick...

Well, that's a good thought, but... both bowls were empty, and I don't have a PV for my secondaries.

Originally Posted by RodKnock

Dumb question. Can't you remove the air cleaner and pour a small amount of gas thru the butterflies instead?

The primary bowl has to fill up a bit -- for the past decade I've usually just cranked it, and cranked it, and cranked it. Spritzing a little gas down the primary will certainly help, but filling the bowls up is even better. Filling it up via the sight plugs is best, since you can't overfill. But filling it via the vents is just as good. Actually, an electric pump is the best way.

[RodKnock]

Originally Posted by patrickt

Actually, an electric pump is the best way.

Ya, I was going to ask about that, but assumed you had an electric pump. And thus, why you needed to do this process in the first place.

[patrickt]

Originally Posted by RodKnock

Ya, I was going to ask about that, but assumed you had an electric pump. And thus, why you needed to do this process in the first place.

No, I have an old-school Carter mechanical fuel pump. They last pretty much forever and provide a nice, even 6 psi, give or take. If you have an electric pump, you just turn the key to fill up the bowls. With a mechanical pump, it's a little more involved when the bowls are empty, but not all that much.

[DanEC]

I don't know about bone dry but my Corvette has to be primed after a couple of days. It has a 60s era bowl vent in addition to the throat vent so it gets cross ventilation to speed up drying out.

My GTX Edelbrock does a bit better - maybe 5 or 6 days before I have to prime. Carters and Edelbrocks have a pretty big fuel bowl vent.

My ERA with 600 Holleys seems to do the best. It's probably good for a week to 10 days.

They probably aren't bone dry at these periods, just too low to charge the accelerator pump and pull fuel in during initial cranking.

After that the amount of throttle pumping and cranking get too excessive for me to bear and I prime the front bowl until I see fuel drip out onto the throttle blade.

[patrickt]

Originally Posted by DanEC

I don't know about bone dry but my Corvette has to be primed after a couple of days. It has a 60s era bowl vent in addition to the throat vent so it gets cross ventilation to speed up drying out.

Jeez, if I had to prime it after letting it sit for just two days I would suspect a nice leak. The accelerator pump ought to get gas to it past that little orange umbrella seal if you just have a half inch, or less, in the bottom of the bowl.

[Texasdoc]

Fill the bowls with the pump. Drain the bowls into a cup. Measure how much comes out. That way you know how much to put down the vent to refill. Easier than removing the sight plugs.

[patrickt]

Originally Posted by Texasdoc

Fill the bowls with the pump. Drain the bowls into a cup. Measure how much comes out. That way you know how much to put down the vent to refill. Easier than removing the sight plugs.

But what if your bowls weren't completely bone dry when you wanted to refill them? If you put the same original amount back in them it would be too much and flow out the boosters.

[Texasdoc]

Originally Posted by patrickt

But what if your bowls weren't completely bone dry when you wanted to refill them? If you put the same original amount back in them it would be too much and flow out the boosters.

If it has been sitting long enough for the fuel to evaporate, then the motor is definitely cold. If it flows out of the boosters then you don't have to pump the pedal/wet the intake with the pump shot before you start it. You want it a bit rich when the motor is cold anyway, right? Me, I just turn on the electric fuel pump.

Patrick, maybe you can design an Accusump style device for the fuel system.

[Bernica]

I just use one of these to pour fuel in through the vent tubes until the bowls are full.

[ame]https://www.amazon.com/gp/product/B002FCJD36/ref=oh_aui_detailpage_o09_s00?ie=UTF8&psc=1[/ame]

[RodKnock]

Originally Posted by Bernica

I just use one of these to pour fuel in through the vent tubes until the bowls are full.

Who are you and what have you done with Bernica?

[patrickt]

Originally Posted by Bernica

I just use one of these to pour fuel in through the vent tubes until the bowls are full.

Uhhhh, twenty bucks for a plastic squirt bottle? I swear you CA guys are just dripping with money.

[patrickt]

Bernica, if you want to step up to what the pros use, I just might be able to get you what I have.... Yes, it's a condiment bottle from Bob's Big Boy with a piece of surgical tubing jammed on the top. Note, however, that it is carefully labeled as to its contents. It don't get no better than this.