Fuel foam in Holley vid.

General engine tech -- Drag Racing to Circle Track

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Coloradoracer
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Re: Fuel foam in Holley vid.

Post by Coloradoracer » Sun Aug 06, 2017 12:11 pm

pamotorman wrote:
Coloradoracer wrote:
pamotorman wrote: 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.

The needle and seat isn't in front of the float, so the notch that is cut and sealed cannot be for it. The needle and seat sit near the pivot.
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Re: Fuel foam in Holley vid.

Post by DaveMcLain » Sun Aug 06, 2017 12:49 pm

Coloradoracer wrote:
pamotorman wrote:
Coloradoracer wrote:

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.

The needle and seat isn't in front of the float, so the notch that is cut and sealed cannot be for it. The needle and seat sit near the pivot.
I think its needed to clear the end of the power valve which sticks out from the middle of the metering block.

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Re: Fuel foam in Holley vid.

Post by pamotorman » Sun Aug 06, 2017 4:34 pm

Coloradoracer wrote:
pamotorman wrote:
Coloradoracer wrote:

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.

The needle and seat isn't in front of the float, so the notch that is cut and sealed cannot be for it. The needle and seat sit near the pivot.
you are correct I did not have my thinking cap on when I posted that. the brass float is cut back there for that reason

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Re: Fuel foam in Holley vid.

Post by pamotorman » Sun Aug 06, 2017 6:43 pm

pamotorman wrote:
Coloradoracer wrote:
pamotorman wrote: 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.

The needle and seat isn't in front of the float, so the notch that is cut and sealed cannot be for it. The needle and seat sit near the pivot.
you are correct I did not have my thinking cap on when I posted that. the brass float is cut back there for that reason to clear the PV

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Re: Fuel foam in Holley vid.

Post by levisnteeshirt » Tue Aug 08, 2017 2:54 pm

I wonder if moving the vent away from the inlet of the mainbody would help the foam , even with just a piece of hose to air with less disturbance

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Re: Fuel foam in Holley vid.

Post by jmarkaudio » Tue Aug 08, 2017 8:57 pm

Moving the vent won't likely help with foam but easily can help keep bowl pressure consistent. Some hood and scoop designs can screw up vent pressure, sending AFR's lean as the car speeds up. Coming is volume pressure, more volume at low pressure creates less. Think of turning on an open hose into a bucket of water, then put your finger over the end to spray it. More pressure, more foam.
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Re: Fuel foam in Holley vid.

Post by pamotorman » Tue Aug 08, 2017 10:24 pm

this is not to keep debris out of the engine. it prevents carb problems caused by hood scoop air turbulence..
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Re: Fuel foam in Holley vid.

Post by MadBill » Wed Aug 09, 2017 12:16 am

Wouldn't the hood-mounted filter do that?
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Re: Fuel foam in Holley vid.

Post by pamotorman » Wed Aug 09, 2017 3:14 pm

MadBill wrote:Wouldn't the hood-mounted filter do that?
yes if you run the hood mounted filter but a lot of people road raced without them. I tried my 68 Z/28 with the thru the cowl cold air cleaner setup without the paper filter and had the same misfire till I installed the L-88 basket. this is the type if air cleaner setup I used. this is the Z-11 set up but the Z/28 was the same
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Re: Fuel foam in Holley vid.

Post by MadBill » Wed Aug 09, 2017 8:33 pm

Ah yes, a lot of people assume the filter is a restriction, but not many verify it. A few years back I was tuning a 700 WHP SB2.2 in a Trans Am Series Corvette. After dialing in spark and fuel on a chassis dyno, we did an A-B-A removing the 3.5" x 16" filter element but leaving the case sealed to the cowl intake and gained..one HP with zero effect on the AFR.
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Re: Fuel foam in Holley vid.

Post by pamotorman » Wed Aug 09, 2017 9:57 pm

MadBill wrote:Ah yes, a lot of people assume the filter is a restriction, but not many verify it. A few years back I was tuning a 700 WHP SB2.2 in a Trans Am Series Corvette. After dialing in spark and fuel on a chassis dyno, we did an A-B-A removing the 3.5" x 16" filter element but leaving the case sealed to the cowl intake and gained..one HP with zero effect on the AFR.
I believe doug roe Q jet book has some tests on air filters and their restriction. I know when at daytona qualifying slitting the paper filter with a razor blade made you go faster till NASCAR caught on. :D the forced air at speed is what causes the turbulence around the carb air bleeds

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Re: Fuel foam in Holley vid.

Post by levisnteeshirt » Thu Aug 10, 2017 7:59 pm

Capture+_2017-08-10-19-55-50.png
Wonder why Grump went to that much trouble just to vent the bowl , always thought it would be better after I saw it in his book years ago , pic from net
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Re: Fuel foam in Holley vid.

Post by pamotorman » Thu Aug 10, 2017 9:05 pm

levisnteeshirt wrote:Capture+_2017-08-10-19-55-50.png

Wonder why Grump went to that much trouble just to vent the bowl , always thought it would be better after I saw it in his book years ago , pic from net
looks like the original vents are plugged because they were allowing fuel to come out and get pulled into the carbs at speed

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Re: Fuel foam in Holley vid.

Post by levisnteeshirt » Thu Aug 10, 2017 9:08 pm

Other pics he had hoses ran to the back of the scoop , just a thought

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Re: Fuel foam in Holley vid.

Post by Bob Hollinshead » Sat Aug 12, 2017 10:43 am

levisnteeshirt wrote:Capture+_2017-08-10-19-55-50.png

Wonder why Grump went to that much trouble just to vent the bowl , always thought it would be better after I saw it in his book years ago , pic from net
notice how the vents favor the front of the car and the needle and seats are positioned towards the rear to work with the sidehung floats.
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