Fuel foam in Holley vid.

General engine tech -- Drag Racing to Circle Track

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Fuel foam in Holley vid.

Postby 1972ho » Mon Jul 31, 2017 7:54 pm

https://m.youtube.com/watch?time_contin ... 91GhyWqfr0 Wow the fuel bowl level almost stood up in the bowls upon launch on this 11.0 second car and it is full of fuel foam I wonder how this can be fixed the jets seems like they would be completely uncovered.

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Re: Fuel foam in Holley vid.

Postby cgarb » Mon Jul 31, 2017 8:01 pm

Sounds like it ran ok, no missing and popping. Holley's have been doing that for a long time...way before the Gopro was invented.

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Re: Fuel foam in Holley vid.

Postby MadBill » Mon Jul 31, 2017 10:00 pm

I just developed a lot more appreciation for BLP Bottom Feed N&Ss. :shock: Probably have to jet down 6 sizes with them!
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Re: Fuel foam in Holley vid.

Postby cgarb » Mon Jul 31, 2017 10:35 pm

Still doesn't account for the g forces. Wonder how an angled spacer would help with that. I'm sure that's why they were made, just would be nice to see the video evidence.

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Re: Fuel foam in Holley vid.

Postby MadBill » Mon Jul 31, 2017 11:27 pm

That's where jet extensions come in...
Somewhere back in the S/T archives there's a vid from RyanBrown Racing that shows the fuel action through a clear-walled float of a perhaps ten second run. At launch, the fuel 'level' is 60°+ from horizontal.
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Re: Fuel foam in Holley vid.

Postby BOOT » Mon Jul 31, 2017 11:50 pm

I'd bet the front jets never got uncovered in that vid despite the highly visible foam. I'd like to know what size N&S, type of fuel, spacer material, some other fuel system details and see him try less psi.
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Re: Fuel foam in Holley vid.

Postby jmarkaudio » Tue Aug 01, 2017 7:34 am

Low pressure with larger N&S will help.

Here is a dyno video with a standard N&S and pressure.

https://www.youtube.com/watch?v=PehQUKwQX8E

Large N&S, low pressure.

https://www.youtube.com/watch?v=FOJKcvTKQAg

Left bowl Standard N&S and pressure, right bowl larger N&S and low pressure.

https://www.youtube.com/watch?v=zftUFW9MfrM
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Re: Fuel foam in Holley vid.

Postby AMXstocker1 » Tue Aug 01, 2017 7:43 am

APD advertises a bowl that eliminates foam there used to be a couple videos of it on youtube but i can't seem to find it, anymore

http://www.apdracing.com/billet-fuel-bowls.html

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Re: Fuel foam in Holley vid.

Postby pamotorman » Tue Aug 01, 2017 7:46 am

MadBill wrote:I just developed a lot more appreciation for BLP Bottom Feed N&Ss. :shock: Probably have to jet down 6 sizes with them!

brasswell was selling those 15 years ago. you had notch the nytrophyl float to clear them if you extended the float out on the arm to get the same leverage as the brass float on the needle seat
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Re: Fuel foam in Holley vid.

Postby 70MC » Tue Aug 01, 2017 9:41 am

This is my friend Chris's car. He doesn't post here but I can find out anything anyone wants. I know it is a LS motor on pump gas in a G body Malibu. This past Sunday he ran a 10.98.
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Re: Fuel foam in Holley vid.

Postby Coloradoracer » Sat Aug 05, 2017 8:50 am

pamotorman wrote:
MadBill wrote:I just developed a lot more appreciation for BLP Bottom Feed N&Ss. :shock: Probably have to jet down 6 sizes with them!

brasswell was selling those 15 years ago. you had notch the nytrophyl float to clear them if you extended the float out on the arm to get the same leverage as the brass float on the needle seat



That float was modified for a sideways application, not a different needle and seat. The bottom feed n&s that BLP sells are a drop in part.
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Re: Fuel foam in Holley vid.

Postby pamotorman » Sat Aug 05, 2017 9:01 am

Coloradoracer wrote:
pamotorman wrote:
MadBill wrote:I just developed a lot more appreciation for BLP Bottom Feed N&Ss. :shock: Probably have to jet down 6 sizes with them!

brasswell was selling those 15 years ago. you had notch the nytrophyl float to clear them if you extended the float out on the arm to get the same leverage as the brass float on the needle seat



That float was modified for a sideways application, not a different needle and seat. The bottom feed n&s that BLP sells are a drop in part.

the epoxy you see in the front center is to seal a notch cut into the float to clear the longer needle seat that uses a Q jet needle. yes it was used in circle track application so the float was angle cut.

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Re: Fuel foam in Holley vid.

Postby DaveMcLain » Sat Aug 05, 2017 9:49 am

Those bottom feed needle and seats can be a mixed blessing. I've had them cause trouble in a circle track application(4412) where they would make the car want to hesitate coming off of the corner. It was as if the seat would close down when the driver lifted off of the throttle and then it took longer or more float drop to get it to open again and for just a split second the fuel level in the bowl would get too low. Going to a conventional needled cured the problem.

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Re: Fuel foam in Holley vid.

Postby pamotorman » Sat Aug 05, 2017 2:20 pm

DaveMcLain wrote:Those bottom feed needle and seats can be a mixed blessing. I've had them cause trouble in a circle track application(4412) where they would make the car want to hesitate coming off of the corner. It was as if the seat would close down when the driver lifted off of the throttle and then it took longer or more float drop to get it to open again and for just a split second the fuel level in the bowl would get too low. Going to a conventional needled cured the problem.

if you don't move the nitrophyl float out further on the float arm you do not have as much leverage as a brass float to close the needle. that is why bo laws says their setup can not be used with a brass float. the float picture I posted has the float moved on the arm to the same distance as the brass float so you need to notch the front of nitrophyl float to clear the extended needle seat
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Re: Fuel foam in Holley vid.

Postby Tuner » Sat Aug 05, 2017 3:39 pm

DaveMcLain wrote:Those bottom feed needle and seats can be a mixed blessing. I've had them cause trouble in a circle track application(4412) where they would make the car want to hesitate coming off of the corner. It was as if the seat would close down when the driver lifted off of the throttle and then it took longer or more float drop to get it to open again and for just a split second the fuel level in the bowl would get too low. Going to a conventional needled cured the problem.

Vapor bubbles form when the pressure drops as the fuel passes through the needle valve and seat orifice, just like vapor bubbles form as the pressure drops when opening a bottle of carbonated beverage.

Prior to introducing the "Window" type needle and seat in the mid-'60s, the externally adjustable Holley N&S had four holes (.093" or so ?) in the same vertical location as the "Window" type. The reason for the larger "Window" (to paraphrase the statements in catalogs and magazines) was to provide more area to allow the vapor to escape above liquid level inside the baffle so the foam could more effectively collapse back into liquid form, rather than be injected below the baffle into the liquid fuel in the bowl. Side-hung bowls have the baffle inserts. In center pivot bowls the hinge bracket is the baffle.

Less fuel pressure (with appropriate N&S size for required flow) reduces foaming because there is less pressure drop through the seat orifice.


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