Autolite 1100 vent valve

[60s Refugee]

I've looked again and again at the plastic vent valve/spring on a 1100. I'll be overhauling my two in a week or so. It looks like little more than a plastic rod sticking in a hole. Its not sealed, and doesn't seem to touch anything other than the spring. The rebuilding directions from "Old Car Manual" site only say to bend a tab to adjust it. No mention of the adjustment is for. No pic or sectional view of the vent. So, what does it actually do?

Harry

 

[fordconvert]

I have never found a clear answer. Like you are observing its not a very tight fit so you would not think it would make a huge difference. Mine broke and fell out while I was doing a cam break in last spring. I have been running since then with nothing in the hole and it does not seem to be hurting anything. I have been meaning to plug it but since its been running fine it just has not been very high on the list.

 

[60s Refugee]

It seems that lotsa' these are being used without the rod. One reason I have taken this long getting another one was that every one I wanted to buy had the rod missing so I didn't. I have even seen some old professional rebuilds that were missing the rod and still sold as complete carbs!

Harry

 

[simon]

I, too, have seen quite a bunch of rebuilt carbs that had the vent rod and spring removed and the vent rod hole plugged.

basic autolite 2- and 4-barrels don't have a vent valve as well, neither do carter RBS and YF (although there were some alterations made depending on year and state, all due to emissions regulations... so it might depend on what car you drive and in which state you live)

 

[Quick 8]

I had this same problem. The little plastic rod kept coming out far enough to jam on the edge of the hole which held the throttle open!! Very dangerous!

I looked into it, and it appears that the piston is an antistall dashpot that is supposed to let the throttle plate close slower if you just instantly pull your foot off the gas pedal. With the extra driveline drag of an automatic trans, if the throttle plate slams closed too quickly, the car can somtimes stall.

Most standard transmissions do not have this at all. It is just plugged. So I pulled mine out and plugged the hole with JB-Weld epoxy. I have a c4 trans, and I have no problems at all with this arrangement. I highly recommend it. I didn't even remove the carb to do this easy mod.

Hope this helps.
~Jim

 

[60s Refugee]

So, you think the vent valve rod acts as sort of a shock absorber for the accellerator pump/anti stall system? I don't see where it could do very much, there is an awful lotta' slop in the fit 'tween the rod and the hole. Maybe that's why the spring is there.

The one I have gettin' ready to rebuild has a metal rod! First time I've see a metal one. It's pretty simple and I think you could make one by taking some brass rod, a brass washer, solder, and wind up with a kobble job that would probably work. Here's a pic.

I am watching three eBay auctions, and another forum member says he might have one. I've bid on three 1100's already this month and lost all three. I just won't pay more than $50 for one that needs rebuilt and is all corroded to hell. Heck, I don't want to pay more than $25. When you add in a rebuild kit, shipping, and missing parts you have almost what it costs for a new Weber 34. Even then, there are worn out places on these that rebuild kits don't cover. You hafta' do what Pony does to 'em and I have neither the machine shop or the know how.

I'm digressing! Anyhow, you just squeezed JB right into the vent valve hole! Heck, I can do that.

Harry

 

[Quick 8]

Yup, it was a lot easier than messing around with the rod. Just make sure you don't push the epoxy in too far or it will block the vent hole that runs to the top of the carb air horn.

I agree that based on the design it doesn't look like it could do much.

 

[Frankenstang]

Here is the description, straight out of the shop manual:

The fuel bowl requires venting to provide proper operation for the various systems. Fuel vapors may form in the fuel bowl when a hot engine is stopped, idling, or operating at very low speeds. By venting the fuel bowl to the atmosphere by means of a vent control valve, engine performance is improved. At higher engine speeds, venting to the carburetor air horn prevents calibration changes due to normal air cleaner contamination.
The restriction of air due to air cleaner contamination causes a pressure drop in the carburetor air horn, and a richer air-fuel mixture. The pressure drop will increase as demand for air (engine speed ) is increased.
The vent control valve connected through linkage to the throttle shaft and located in a bore over the fuel bowl, is at the inward position during closed or part throttle operation. In this position, the valve allows venting only to the atmosphere. At normal or wide open throttle operation the valve moves outward, sealing the external vent and opening the vent to the carburetor float.

Okay, probably more than anyone really wanted to know, but hopefully there is some useful info in there. The two interesting take aways I had from reading this 1) venting essentially helps prevent vapor lock (if I understood this correctly) 2) bowl vent serves almost like a bypass for air horn, when air filter is dirty

They're most often referred to for their rebuilts, but I believe you can get parts for these (eg rod, or valve) from pony carburetors. At least their site shows that they still sell parts for the 1100. I'm pretty sure they restore this function on all their rebuilts, and it even looks like it comes with one on the new 'vaporizer' according to the picture. I plan on checking with them for a float, because I can't seem to find one here local, or a kit that comes with one. I've also seen several of these carbs with the vent rod setup removed. I think this was standard practice for rebuilders.

-Robert

 

[60s Refugee]

Well, that explains much. Guess it wouldn't need a perfect seal to direct most of the vapor. Also shows the need for proper adjustment!

Harry