Upgrade for check ball style acc. pump on Holley float bowls

[Troy Patterson]

I've had a collection of older Holley float bowls I've had to remove due to mediocre functioning accelerator pumps with aged, old style check ball system.

In some cases, some guys need to keep the vintage carburetor's appearance authentic, so it was necessary to retain the original float bowl (or at least the original float bowl style) so I've modified them when their accelerator pumps no longer worked, and I've not wanted to throw otherwise good float bowls away so, I devised a way to upgrade them to use the modern umbrella style check valve.

I'll have a picture or two up in a while.

Troy Patterson TMPCarbs.net TMP Carbs

[af2]

Just thinking out loud but would not a ceramic ball be better? I was thinking weight and longevity.

[Troy Patterson]

The umbrella check valve style responds faster because it doesn't require fuel to pass by it to move the check ball to a seated position before fuel moves toward the discharge nozzle. The faster response is better with a performance application.

The lighter check ball is good and would response faster than the steel or aluminum check ball, but still not as desirable in my opinion. The umbrella check valve seals with very little pressure and movement. It only really comes away from a sealed position (not saying it's sealed just sitting there) when fuel is drawn into the accelerator pump cavity.

Troy Patterson TMPCarbs.net TMP Carbs

[MadBill]

Might not the umbrella design be more susceptible to "resonant vibrational pumping", aka high frequency shooter dribble?

[Troy Patterson]

I am retro-fitting it to Holley float bowls with check ball style valves that would otherwise be thrown away with accelerator pump check valves that do not work for a variety of reasons. I have covered the gauntlet with repairs to this style of accelerator pump and check valve over the years with marginal success at best.

Do accelerator pumps with umbrella style check valves pump fuel as a result of resonant vibrational forces where check ball style check valves do not? No, not in my experience. In fact, I've never experienced such a problem that I can recall. Tunnel ram applications where the engine's vibrations and harmonics are amplified due to the leverage of those forces afforded by the height of the tunnel ram itself on the carburetor(s) well, yes, there's a whole lotta shaking going on there of everything in the carburetor in some applications, the remedy is vibration absorbing spacers.

Are umbrella style accelerator pump check valves more susceptible? Maybe, but if it's not a problem, does it matter?

Troy Patterson TMPCarbs.net TMP Carbs

[MadBill]

I agree that damping the vibration is the best approach. Reducing same likely also cuts N&S and other component wear as well as bowl foaming.

Wilson list damper gaskets for only a couple of bucks, but they never seem to have them or the steel-backed rubber washers for under the hold down nuts in stock... http://www.wilsonmanifolds.com/shop/ind ... tail&p=106

[The_Countdown]

Troy,
Any pictures of this available yet? This is something I've thought about, but never took the time to experiment with it.

Thanks

[DaveMcLain]

How about in a hot soak situation is the elastometer valve style check more prone to forcing fuel out of the shooter than the ball type which would allow built up vapor/pressure to escape back to be bowl?

[JDR Performance]

How about in a hot soak situation is the elastometer valve style check more prone to forcing fuel out of the shooter than the ball type which would allow built up vapor/pressure to escape back to be bowl?

They WILL do that sometimes. You can see the squirter nozzle spray fuel out as the car sits. There's a fix for that too.

[Procharged 434]

How about in a hot soak situation is the elastometer valve style check more prone to forcing fuel out of the shooter than the ball type which would allow built up vapor/pressure to escape back to be bowl?

They WILL do that sometimes. You can see the squirter nozzle spray fuel out as the car sits. There's a fix for that too.

I know this thread is ancient, but I so happen to be dealing with a problem with a quick fuel Q-750 currently doing the very thing when the truck is shut off. You can sit there and watch it spit fuel out of the primary nozzle. What got us to looking at it, is while we were testing it on the street, only drove about a mile, romped on it once just testing it, and then back to the house, we had it fall on its face going to wide open throttle from a dead stop, but only one time, most of the time it opens up without a problem at all. I let out of it, immediately stomped it back open, and it opened up without a problem and starting smoking the tires on the second attempt. With the engine shut off, you can throttle the carb by hand, and sometimes it appears that it only squirts a bit of fuel, and you can hear air in the system. Other times it will squirt nice solid streams like it is suppose to. It has a good green alcohol pump diaphram, nothing wrong with it. It has a pink pump cam. The pump arm is adjusted correctly with .015" of clearance at WOT position. The only thing I can think of that may be the problem is the Umbrella check valve? I can't figure out how it is getting air in the system though, since it gets it fuel supply from the bottom of the bowl? Could you go into more detail of what the issue is and how to fix it? Only seems to happen on the primary side so far.

Thanks!

[Procharged 434]

btw, our application is a 1989 GMC short bed 2wd truck with a mild 350 and with a B&M 144 supercharger/ 6 psi boost, Comp Xtreme Marine 270H camshaft 226/236@.050 112° lobe seperation, Timing is locked at 36°, using a Mallory 685 to pull timing back to 30° under boost. 700R4 trans and bone stock 1400 stall converter(needs a higher stall converter bad! Lol).

[Walter R. Malik]

Just thinking out loud but would not a ceramic ball be better? I was thinking weight and longevity.

Probably ... but, you need to remember the target of production parts;
if BEST will cost more then it won't be used ... ADEQUACY is all that is necessary

[steve cowan]

btw, our application is a 1989 GMC short bed 2wd truck with a mild 350 and with a B&M 144 supercharger/ 6 psi boost, Comp Xtreme Marine 270H camshaft 226/236@.050 112° lobe seperation, Timing is locked at 36°, using a Mallory 685 to pull timing back to 30° under boost. 700R4 trans and bone stock 1400 stall converter(needs a higher stall converter bad! Lol).

I had this happen to me at the track a few years ago on my 950 hp carb
I replaced acc/ pump diaphragm and umbrella as well,there was nothing visible but it fixed the issue
The problem occurred with cold engine so I think it wasn't a heat soak / vapor issue.
The last few years now I replace these items prior to start of race season and it has not happened again.