3x2 center carb vent control arm and valve missing

[Flareside]

I just noticed that the center carb on my '68 tri-power is missing the bowl vent assembly I see in other pictures. The float bowl doesn't even have provisions for the vent. Should I be concerned about it? It's a lever that opens a vent on top of the float bowl when the throttle is closed.

The car does have hot start problems on occasion (excessive cranking), but I just attributed it to the carbs needing a reconditioning. (just had Jerry Luck on the phone tonight, but he's got a 6 week waiting list!)

[Jerry Clark]

Re: 3x2 center carb vent control arm and valve mis

Hi Flair, ( you really should trust us with your name ):

This usually happens when someone replaces the correct primary fuel bowl with one designed for a four barrel or a secondary carb rather than ordering a correct primary bowl.

I agree six weeks is a long time to wait for Jerry Luck but he will have the parts as this assembly was missing from mine also, ( Holleys Custom Shop didn't feel the need to replace it when they botched the first restoration / rebuild ), however Jerry did and did. The picture I sent you is of my Jerry Luck carbs.

jer

[Joe Kayser]

Re: 3x2 center carb vent control arm and valve mis

Hi Jerry,

Real names Joe Kayser. I've been using "Flareside" in discussion forums for years, so I never really give it a second thought. It's definitely not a trust issue, at least not with Corvette enthusiasts. I'll use my real name at NCRS from now on.

Do you know what purpose the bowl vent serves? Since the bowl is always vented through the carb body, I'm not clear why you need it.

[Jerry Clark]

I Wanna Know Too

Hi Joe, ( I like that a lot more ) :

As long as we are being completely trustworthy here, I dodged that part, of all the articles I've read and I have owned nine tri powers, I have never understood the vent but you can bet there are gonna be more than a few friends here who will take the opportunity to straighten us out, FINALLY. Have at us guys, inquiring guys wanna know

jer

[Wayne M.]

Re: 3x2 center carb vent control arm and valve mis

F-side --- Maybe it never had an idle bowl vent. Example; I have a 4055-1 carb with an 862 (late '68 or early '69) date which has NO vent, and another 4055-1 with a 981 date which DOES. There is something published somewhere on the introduction of the vent, and I'll dig it out if you need it. This was discussed a WAY back (archives).

3 x 2 fuel bowls are unique, because of the fuel inlet machined to the drivers side.

[Jerry Clark]

Re: 3x2 center carb vent control arm and valve mis

Wayne:

3 x 2 fuel bowls are unique, because of the fuel inlet machined to the drivers side.

Forgot about this characteristic, exactly but I bet you know what the vent is supposed to be for ?

jer

[Jerry Clark]

Well Joe...

I don't feel nearly as bad as I did yesterday. Evidently while we don't understand the intended purpose of the fuel bowl vent , the other guys don't either.

I will look over thirty years of saved articles and see what I can find and if that is not productive I'll give Mr. Luck a ring, he owes me one anyway.

Best of Luck

jer

[Joe Kayser]

Re: Well Joe...

Oh well, thanks for trying Jerry. I didn't think there was ANYTHING about these cars that would stump this group!

Don't give up, I'm sure somebody knows what the extra vent does...

After further research, it looks like some late 68's had the vent, and some early ones didn't, but nobody knows for sure. Anybody know the real deal?

-Joe

[Wayne M.]

Re: Well Joe...

Joe --- I'm sure Jer will find something on this bowl idle vent; I started to look myself, yesterday, but had other pressing matters --- maybe today. Main thing is: don't throw out your vent-less bowl yet.

[Jerry Clark]

Re: Well Joe...

Joe & Wayne:

Well, rather than to "look" through all that crap I cheated and called Mr. Luck, no Luck, he will call back and if his answer differs from this one I'll post it.

From a friend at Holley, (kinda), the bowl vent was designed to "stabilize" the fuel in the bowl when the engine is shut down, Hmmm., seems they thought pressure, under what circumstances I can't imagine, might occur in the bowl and this was its relief valve. The vent was removed as a possible hazard soon there after, ( probably along with the designer ) . I don't like this response but right now it's all I have, interesting though, he is a sharp guy and has been around since forever.

jer

[Wayne M.]

Re: Holley Bowl Idle Vents

Jerry --- Came across one article in the RESTORER by Gary Hodges, Fall '92. Lists Metering body #'s, and whether idle vent equipped (or not). I'll summarize his table:

WITH Idle Vent: All '66 s; all '67 single carb cars, except L88; '68-69 tripowers with the "dash-1" after the list # (ie. 4055-1, 4056-1); '70 LT1's; nothing for '71 LS6's or '72 LT1's. So it appears to have been used intermittently over a 4-year period.

As to the why, your source is probably on to something. I definitely think it has to do with gas boiling in the bowl under extended idle periods. In some other models, this was cured by a hot idle compensator, which allowed additional air bleed into engine to counter the excessive richness. But in the case of idle vents, they just decided to let the excess vapour escape to the atmosphere, rather than dump into the intake, so as not to kill the engine at idle. Just a thought.

[Rich Garguilo #33425]

Re: Holley Bowl Idle Vents

I read this out of one of my old tech manuals.A hot engine can cause fuel in the main well to boil,causing too rich a fuel mixture,stalling,and hard starting of a hot engine.The vent valve allows fuel vapors to escape the main well.When vapor canisters started being used in the 70's a hose went from the carb vent to canister.

[Jerry Clark]

Re: Holley Bowl Idle Vents

Hi Rich:

I like this explanation now I just wish I could recall ever seeing the replacement vent hose on any application.

jer

[Joe Kayser]

Re: Holley Bowl Idle Vents

Sounds like you nailed it Wayne. My center carb is indeed a 4055, not a 4055-1. I always wondered what the "-1" meant. It's the vent...

Thanks!

[motorman]

Re: 3x2 center carb vent control arm and valve mis

if the bowl had a external vent i would assume the the throttle arm would have the extension to move the linkage.