C2 3810 Carb Question

[Mike Swanson]

It has been a while since I took the carb off and am putting everything back together now. I notice something that doesn't quite look right, or at least I don't remember it looking this way.

I have attached a photo of my Holley 3810 to illustrate ny question:

On the front of the carb there is a black rubber disc attached to lever. With everything at rest and carb return spring installed, the rubber is away from the bowl. If I open the throttle a bit it seems to seal against the bowl.

Is this normal?

Thanks as usual for all your help

Mike

[Wayne K.]

Re: C2 3810 Carb Question

Mike,

Yes this is normal.

Wayne

[Mike Swanson]

Re: C2 3810 Carb Question

Thanks Wayne,

I just wanted to check since I don't need gas spewing everyehere when I fire her up this weekend.

Mike

[Wayne K.]

Re: C2 3810 Carb Question

Mike,

If your float is adjusted properly and your needle/seat is good you should not be concerned about fuel coming out the hole. I would suggest after connecting everything to pull the coil wire so the car won't start and crank it over to fill and pressurize the system to check for leaks before actually running the car.

Wayne

[Mike Swanson]

Re: C2 3810 Carb Question

Wayne,

I will definitely follow your advice. I don't really anticipate any problems since I didn't adjust anything when I took it off and everything was fine before removal but it is best to be safe here.

Thanks again for the wise advice.

Mike

[Gerard F.]

Idle vent, what's it for?

Mike,

It is supposed to be open at idle, but maybe not as much as yours. The adjustment of the gap is confusing depending which manual you are going by.

I have often wondered what the vent does and what the consequences are if one were to plug it or adjust it so that it was always closed. It seems to me that the vent hole guarantees that your engine compartment will always smell of gasoline, and that if your float sticks you will be spewing gasoline over a hot intake and exhaust manifold.

Later model Holley's eliminated the vent hole, I guess in response to emission control regulations. There is a 68 holley which uses the same metering block (4743) which has no vent hole.

So, maybe one of the carb experts out then can tell us what the consequences are of plugging the vent hole or adjusting it to zero clearance.

Jerry Fuccillo
#42179

[Rob A.]

Re: Idle vent, what's it for?

I bought a good Holley carb book before I rebuilt my '66 #3367 carb. The old style, external idle vent, according to the book, prevents fuel from boiling during extended idle periods by letting heat out. I don't have any fuel spilling out, and if you do, just adjust your float level until it doesn't.

[Gerard F.]

Re: Idle vent, what's it for?

Rob,

I was just wondering if anyone has tried plugging the vent hole, and seen any difference in performance or idling. On a 3810 and most 67 holley's, it is a major project to adjust the float with non-externally adjustable float bowls. You have to take the bowl off to adjust it, or replace the needle valves. (One of GM's worst cost cutting nightmares to save a few bucks, I think it only lasted one year.)

I noticed in Chev by the Numbers book that a 4210 (68 Camaro, 302) uses the same 4743 primary block as the 3810 and 3367 but does not have the idle vent. I really wonder how necessary the idle vent is, the way we now use our baby's these days.

I might try it once I replace the double pumper (4776) on my 67/327 with the original 3810 I'm working on now.

Jerry Fuccillo
#42179

[Rob A.]

Re: Idle vent, what's it for?

Jerry,

Didn't realize I was fortunate to have externally adjusted floats on my #3367. The original #3367 I rebuilt and put on my '66 is doing fine, no leaks, which I really appreciate since I drive the car almost every day. I didn't recolor it or anything fancy, just the standard Holley renew kit. Good luck with your #3810.