Weber carb and possible vacuum hose

[DarwinT]

My Midget had a Weber carb. There is a tube sticking out of the side of it that looks like a vacuum line should be hooked to it.


https://i2.photobucket.com/albums/y2/darwin-t/CARB.jpg

What is it for? Should I plug it up? Hook something to it?

Thanks.

 

[lbc_newbie]

That's the vacuum advance for your distributor. Now, I've been told, that with the Weber set-up, it might not be necessary. I know someone on the Forum here will clarify that for us Weber guys.

 

[DarwinT]

That's the vacuum advance for your distributor. Now, I've been told, that with the Weber set-up, it might not be necessary. I know someone on the Forum here will clarify that for us Weber guys.

My vacuum advance is hooked up to the intake manifold.

 

[lbc_newbie]

Should be fine where it's at and you don't have to tap or drill into your manifold.

 

[DarwinT]

lbc_newbie,

My vacuum advance hose is hooked to the intake manifold and nothing is hooked to the thing on the carb. If both are equal vacuum sources, I should plug up the unused one, right? And then re-adjust the carb.

I can't start it right now because I have the exhaust off. I got my Harley muffler today.

 

[Roger]

I know little about Webered Midgwets, but in my experience it's unusual to connect vacuum advance to the inlet manifold, but rather to the carb. They are not, to use your expression, equal vacuum sources.
For example, on closed-throttle overrun, you have maximum depression in the manifold. Do you want maximum advance under that condition? Probably not!

 

[DarwinT]

That's what I thought! I assumed the guy that sold the car to me knew what he was doing - he had built two dragsters which are stored in his barn. He isn't physically able to drive them any more.

I'll change the vacuum line to the carb and plug off the one to the manifold then.

Thanks.

 

[jvandyke]

maybe you can use the manifold source to help with crank case venting, made a world of difference on my Weber equipped 1098 (BTW I don't remember where my vac adv. line hooks up, pretty sure carb base, but I'm going to look now)

 

[bthompson]

I have my distributor advance disconnected entirely. (Weber carb, 45D dizzy.) I think I got the tip from John Twist: just make sure the mechanical advance maxes out at 32 degrees BTDC, and let the idle timing fall where it may. I'm <span style="font-style: italic">way </span>off of the recommended 2 ATDC idle this way, which causes some hard starts when it's cold. Not the ideal solution, but it runs well enough.

 

[regularman]

That tube at the bottom of the carb comes before the butterfly in the carb IIRC. and gives vacuum when the throttle is opened, but very little at idle. The intake vacuum would be just the opposite with the vaccum at max at idle and minimum at full throttle. I put a tap in my pierce manifold and ran it to the valve cover vent to stop the oil leaking when the engine is running and this worked great.

 

[DarwinT]

Fixing that should make it run a lot better. I had a lack of power and vibration at lower RPMs. I had to floor it to get up to speed. That was no big deal, because I ALWAYS floor it.

I'll need to adjust the carb again. I'll start a new thread on that subject.