groho

Discovered my Edel performer carb is nowhere near the task for autocrossing, so I've moved up in the evolutionary chain and plan to build a holley 600. Through the grace of goodness I was given a 4150, 600cfm, vac sec, center hung, dual feed, but I believe its an older model because the vent tubes are part of the main body casting. They're not flush using a brass inserts. Can anyone provide some insight? I plan to use aspects of the offroad avenger in this setup; road course floats, jet extensions, spring needle/seat, and a QFT adjustable secondary kit. The cast vent tubes prevent me from installing a one-piece cross over and still clear the air cleaner lid. Any ideas around that? Second, understand jet extensions are used in the secondaries and hard launches, but has anyone considered them for the primaries to overcome hard braking and deceleration?

barnett468

hello;

i would be hesitant to use a mechanical secondary of any kind for auto cross.

what cross over are you referring to.

are the vents brass or part of the carb top.

they only need to be around 1/2" high.

jet extensions in the front are unnecessary. if it stalls under hard braking your float level is typically too high. i run the gas level a bit below the bottom of the inspection holes.

can you post a photo?
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Gun Jam

I think he said it was a vac second.

What does not appeal to you about mech 2nd in auto cross? if anything it seems it would provide smoother more predictable power than a vac 2nd.

barnett468

hello;

yes he obviously did say vac. you are being to kind, lol. i'm obviously a moron. i see vac now. no idea how i missed it.

unless one is an extremely good tuner the mechanical secondary will bog in auto cross at the lower speeds you go which will cost time. vac secondaries can be adjusted with springs to open sooner or later. same with the eddy carb. this make for a more consistent and smoother power.

if you hit the mechanical secondaries too soon in a low speed corner and the car bogs then recovers, it will send you off track and likely over a few cones.

11 time world auto cross champ mary pozzi uses efi. its much better for this app.
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Gun Jam

Thanks for your input!

groho

Carb vs EFI = free vs $3000. Pretty much a no brainer for me, this is why I'm using a center hung, 600, dual feed, tuned for road racing. Back to my original question, the cross over tube is the one-piece vent tube that replaces the two individual vent tubes. It prevents the fuel from exiting the vent tube during extreme angles and hard turns and still allows for the bowls to ventilate. My vent tubes are part of the casting, not brass. The list # is an 80145

69mach1377

Taller air cleaner lid?

barnett468

ok, i know what you are referring to with the cross over now.


yes, you mentioned that in your first post.


just shorten them like i said in my first post. you can also shorten the legs on the crossover. i could do this in 30 minutes, its a piece of cake.


here is the carb style you have. what is your question exactly?
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here is a carb with a cross over

Gun Jam

okay...I gotta ask.

Those are just vent tubes that allow air to enter to float bowl to prevent vacuum and allow the fuel to be drawn out by the idle and primary circuits correct?

How could adding that stupid tube full of holes do anything other than possibly restrict fuel flow out of the floats and **** up everything?

-Gun

barnett468

yup!



Well, the holy tube is "supposed" to be designed so that the holes in the top equal the total area of the holes in both of the vent tubes it is jambed into.

the carb i posted is called the "low rider". it is designed for low riders that jack their car all around with their hydraulics while they are driving. I KID YOU NOT, lol. It says so in the holley description.

They basically prevent gas from sloshing out of the vent under extremely extreme conditions, like when you flip your car over on the roof on the straight away at daytona like tony stewart likes to do, or when one does one of those super scary death defying barrel rolls with their car etc.. it also helps if you drive your car on rough water where the waves can jostle it around or when doing the double jumps in off road stadium races or even at the Tecate 500, which until recently, I thought was a drinking contest : ) FYI, that is a smiley face

Now, if one shortens the height of the tube, it kinda defeats the purpose of it by only allowing partial roll overs before gas comes spewing out of the vents : ) That is another smiley face.
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