Fitting for '56 Dual Quad Carbs

[Brooks G.]

Guys, I am still working on my 1956 trying to eliminate one problem at a time. When the engine is cranked, I have a vacuum leak on the back of the rear carburetor from a threaded hole where I believe the vacuum advance line would plumb in. My distributor is mechanical advance and has no provision for a vacuum advance line. Does anyone have a picture of what the correct fitting or plug looks like for a dual quad carburetor system like I have? Thanks in advance. Brooks Glover (2141)

[Tom B.]

Re: Fitting for '56 Dual Quad Carbs

I checked a '56 set I have in the garage but it has a newer brass hex plug in it, not correct. I have a rear carb throttle plate in my WCFB parts box that had a square head pipe plug in it. This may be original. When I took it out I found someone had over tightened it and cracked the casting. When you find the right part be gentle when you install it. These castings are fragile around that hole.

Tom

[Alexander C.]

Re: Fitting for '56 Dual Quad Carbs

I ordered a plug from CC to fill the hole. The plug they sell fits well and blends in very nicely.

[Brooks G.]

Re: Fitting for '56 Dual Quad Carbs

Tom and Alexander, thanks for your reply to my post. Tom, the fitting you mentioned sounds like it could be the one I am looking for. Alexander, do you have a part number for the one you are using? I am also wondering if it is hex shaped or square. All dual carburetor pictures I have show either the front or one or the other of the sides. What I am looking for is on the bottom of the rear carburetor. Thanks again! Brooks Glover (2141)

[Alexander C.]

Re: Fitting for '56 Dual Quad Carbs

I used 351064, my 1x4 carb has the vacuum port on the rear at the bottom. I'll be watching this thread though in case anyone comes up with something more factory correct!

[Edward M.]

Re: Fitting for '56 Dual Quad Carbs

Guys, I am still working on my 1956 trying to eliminate one problem at a time. When the engine is cranked, I have a vacuum leak on the back of the rear carburetor from a threaded hole where I believe the vacuum advance line would plumb in. My distributor is mechanical advance and has no provision for a vacuum advance line. Does anyone have a picture of what the correct fitting or plug looks like for a dual quad carburetor system like I have? Thanks in advance. Brooks Glover (2141)

Sorry, Brooks, I forgot to check my two 56 single four WCFBs last night. I'll do that, and check the parts book and see what it says.

I am pretty sure the rear fitting is not for vacuum advance. My 56 Belair carb has a fitting in the rear to provide vacuum to the vacuum operated windshield wipers. The vacuum advance for the distributor is another port on the base plate.

I sent myself a note to check this all out for you. Sorry I missed your call last night.

[Bob B.]

Re: Fitting for '56 Dual Quad Carbs

Brooks,

My best guess is that it is plugged with the standard pipe plug, a small one with the square head.

There is another fitting that is used if vacuum is needed for a washer vacuum canister. I'm out of town, but I think you can see this one by looking up washer items on Zip or other supplier websites.

What kind of fitting do you have in the same place on your other carb?

Bob

[Steven N.]

Re: Fitting for '56 Dual Quad Carbs

If your car has a powerglide , shouldn't you have vacumm at the base of the rear carb. The fitting that goes on a fuel injection for vacumm is the same fitting. it has a square block with a tube.I'm , doing a dual quad with powerglide and that is the fitting i've found to be correct, works perfectly
Best of luck
Steven j...................

[Edward M.]

Re: Fitting for '56 Dual Quad Carbs

If your car has a powerglide , shouldn't you have vacumm at the base of the rear carb. The fitting that goes on a fuel injection for vacumm is the same fitting. it has a square block with a tube.I'm , doing a dual quad with powerglide and that is the fitting i've found to be correct, works perfectly
Best of luck
Steven j...................

56 & 57 Powerglides did not have vacuum modules. That started in 1958.

[Steven N.]

Re: Fitting for '56 Dual Quad Carbs

Its also the source for vacumm on the wiper washer system ..........I belive ?

Steven j.

[Edward M.]

Re: Fitting for '56 Dual Quad Carbs

Its also the source for vacumm on the wiper washer system ..........I belive ?

Steven j.

56 & 57 used foot pedals for the wiper washer system. On 56 & 57 cars, this is a plug. Just not sure what the plug looked like.

[Edward M.]

Re: Fitting for '56 Dual Quad Carbs

OK, here is what I found. My 2366SA carb has a hex head plug in the rear base area (see pics). Both the 56/57 AIM and the 56 Chevy Passenger car AIM list part numbers 444819 / 444820 (with the phrase OPT) as the part for this plug.

Both AIMs also picture this plug as a hex head plug, wich leads me to believe that the one in the pictures is correct. No telling how or when the orange paint ended up on the head of the plug. My suspicion is that this should be a natural finish.

Brooks, you are welcome to this plug if you want it.

[Brooks G.]

Re: Fitting for '56 Dual Quad Carbs

Thanks Ed, a picture is definitely worth a thousand words!
Brooks Glover (2141)