VENT TUBES ON YOUR CARBS..........

Posted By: Thumperdart

VENT TUBES ON YOUR CARBS.......... - 02/28/09 10:53 PM

I was talking to a member on here about my bowl vent tubes and the possibility of vaccum pulling fuel from them at speed so, what do you guys do if anything to eighther extend or re-locate to avoid this issue if it even is one.....Thankxx....

Posted By: RemCharger

Re: VENT TUBES ON YOUR CARBS.......... - 02/28/09 11:07 PM

Just a thought... if you're running out of fuel, its hard to believe the level is high enough that it can pull over...espescially in high gear..

Rem

Posted By: mopardad

Re: VENT TUBES ON YOUR CARBS.......... - 02/28/09 11:16 PM

run a piece of rubber fuel line from one to the other looped about 3" high in the center with a slot cut in to the top of the high point of the tube

Posted By: Thumperdart

Re: VENT TUBES ON YOUR CARBS.......... - 02/28/09 11:25 PM

I`m looking at any and every possibility to explain the 99 jets in this thing. I did have rubber extensions and now I tied the two together with a long slit 1/8th wide in the BOTTOM of the bend so it clears the air filter top/scoop.

Posted By: ToddP

Re: VENT TUBES ON YOUR CARBS.......... - 02/28/09 11:32 PM

What size is the high speed air bleed?
Too large will cause lean condition on Dominator at wot.

Posted By: Anonymous

Re: VENT TUBES ON YOUR CARBS.......... - 02/28/09 11:34 PM

Quote:

I`m looking at any and every possibility to explain the 99 jets in this thing. I did have rubber extensions and now I tied the two together with a long slit 1/8th wide in the BOTTOM of the bend so it clears the air filter top/scoop.

with the air cleaner on it normally wouldn't be an issue. and you don't want the slit on the bottom since the incoming air (to the carb) could potentially create a siphon effect on it.
without the air cleaner on is when you would normally see a problem, mostly at high speed from the air rushing into the scoop and over the vent tubes. that's when a tube connecting the vents and a narrow slit on the top or side side might help.

Posted By: 2QUICK4U

Re: VENT TUBES ON YOUR CARBS.......... - 02/28/09 11:42 PM

Quote:

run a piece of rubber fuel line from one to the other looped about 3" high in the center with a slot cut in to the top of the high point of the tube

dom are you running a dominator or 4150? when i ran the 4150 car was quick out of the hole but slowed on big end,went to dominator car left good but came on the big end and picked up et and mph..never went back to 4150

Posted By: MR_P_BODY

Re: VENT TUBES ON YOUR CARBS.......... - 02/28/09 11:56 PM

Looks like this

Posted By: Quicktree

Re: VENT TUBES ON YOUR CARBS.......... - 02/28/09 11:59 PM

Quote:

Looks like this

is that pic from the 50s?

Posted By: 10 o to go

Re: VENT TUBES ON YOUR CARBS.......... - 03/01/09 12:13 AM

we run 90 degree spark plug boots and put a tube drilled holes in tube across .
don

Attached picture 5060295-challengerfavorite.jpg

Posted By: dthemi

Re: VENT TUBES ON YOUR CARBS.......... - 03/01/09 12:14 AM

Quote:

run a piece of rubber fuel line from one to the other looped about 3" high in the center with a slot cut in to the top of the high point of the tube

Same here, and if the float sticks is less likely to burn your car up, and it dumps into the carb. Not good for the cylinders, but it's the lesser of evils I think.

Posted By: Thumperdart

Re: VENT TUBES ON YOUR CARBS.......... - 03/01/09 12:14 AM

I`m running an 8082-3 hp 1050 dominator w/ 25 hi-speed bleeds in the rear and I believe 31`s ft. w/90`s and a 3.5 pv-and 99`s w/out.

Posted By: MR_P_BODY

Re: VENT TUBES ON YOUR CARBS.......... - 03/01/09 12:25 AM

Quote:

Quote:

Looks like this

is that pic from the 50s?

Why do you say that Tony

Posted By: ToddP

Re: VENT TUBES ON YOUR CARBS.......... - 03/01/09 12:35 AM

Try .025"s in the front as well.
This may help.

Posted By: moparacer

Re: VENT TUBES ON YOUR CARBS.......... - 03/01/09 12:43 AM

I always thought that would change the fuel curve?

I have ran all sorts of hood scoops and air filters and carb combs never had to do that hose trick...

Posted By: Thumperdart

Re: VENT TUBES ON YOUR CARBS.......... - 03/01/09 12:48 AM

We tried smaller bleeds in the ft at the chassis dyno and it went dead rich but, havn`t tried it at the track yet.....was told that`s WAY too rich but if I race on the 8th I`ll try it.

Posted By: MR_P_BODY

Re: VENT TUBES ON YOUR CARBS.......... - 03/01/09 12:51 AM

Quote:

we run 90 degree spark plug boots and put a tube drilled holes in tube across .
don

I'm sure that looks better but if you needed more
vertical column you would have to loop it up, the
loop has about 4" more vertical column

Posted By: ToddP

Re: VENT TUBES ON YOUR CARBS.......... - 03/01/09 12:53 AM

It should, that is change the fuel curve in the primarys to not run lean at wot

I would also measure the kill bleed in the metering block.

Also how many emulsion bleeds in the main well are drilled 2,3,or 4?

does the metering block use a tube in the main well to feed the idle circuit?

I run my dominator high speed bleeds the same size as the kill bleed in the metering block.Same size in primary and secondary .026"

Posted By: MR_P_BODY

Re: VENT TUBES ON YOUR CARBS.......... - 03/01/09 01:05 AM

Dom, is your scoop sealed, if so you wont see a vacumn
in the scoop area, specially on top end, that area will
be under a slight pressure, about 5"-8" of water at
your speed. The loop tube is for a hard leaving car,
when you launch the fuel sloshes up and out of the vent
falling into the carb causing the carb to go dog rich
EDIT
also a set up that didnt have a air cleaner and
usually no hood, the air passing over the carb would
suck fuel out of the vents and spray on the windshield

Posted By: ToddP

Re: VENT TUBES ON YOUR CARBS.......... - 03/01/09 01:09 AM

You will no doubt have to take main jet out after reducing the hs air bleed size.

It seems like your current carb set up is lean on the primary and rich on the secondary.

Also I would measure the power valve channel restrictors to determine proper jet stagger.

99 is a very big jet.

Posted By: tjmarcus1

Re: VENT TUBES ON YOUR CARBS.......... - 03/01/09 01:19 AM

dom, i've never had a prob with the carb sealed. if it's not sealed or if you are not running a hood, then you might need those ugly hoses. either way, don't put the slot on the bottom of the curve. i don't like the hoses because i don't like anything messing with airflow.

Posted By: dthemi

Re: VENT TUBES ON YOUR CARBS.......... - 03/01/09 01:30 AM

The neatest ones I've seen are 180 tight radius bends of tubing the same size as the vent tubes connected with compression fittings pointing down at the carb.

Posted By: Thumperdart

Re: VENT TUBES ON YOUR CARBS.......... - 03/01/09 01:52 AM

Lots of ideas here.........I don`t know all of the specs on these metering blocks as far as the holes you mention but I`m taking the carb apart to fully clean and re jet so I`ll check. My carb is sealed to the scoop and actually picks up 1 mph and a bit of et w/out the air filter so that`s how I race it. Thankxx guys.

Posted By: tjmarcus1

Re: VENT TUBES ON YOUR CARBS.......... - 03/01/09 02:49 AM

did you say it picks up et and mph without the seal?

Posted By: Thumperdart

Re: VENT TUBES ON YOUR CARBS.......... - 03/01/09 02:53 AM

Sorry tj, I just fixed it.

Posted By: tjmarcus1

Re: VENT TUBES ON YOUR CARBS.......... - 03/01/09 03:10 AM

not trying to hi-jack, but did i tell you i have a 72 dart? [actually, it's my son's that i bought for him when he was maybe 16]

Posted By: Thumperdart

Re: VENT TUBES ON YOUR CARBS.......... - 03/01/09 04:08 AM

72 Darts rock don`t you know.

I got your photos....nice stuff thankxx.