Hot Rods Rochester 2GC Small Base Carb Help

Does that apply when in my case the 2nd carb is a secondary carb???

 

Not sure, remembering I am not expert, but figured it acted as a choke at start up.
It does not seem to be all that effective and I over rode it during my 1st cold start, but later it seemed to open up as I would expect, but did not close too well at cold start...

 

Since firing the engine up and being able to get it to idle, I have adjusted the left screw to hold idle at 1000rpm , anything below it would pitter out.
The left screw I have not touched It seems the linkage is hold that throttle plate closed until it is opened as a secondary carb.

 

The fast idle cam is missing from the carb on the right.
With a manifold of that design, fuel distribution at anything below full throttle is unequal front to back if you run it with progressive linkage. Will it run? Probably. But it will run better with solid linkage and both carbs identical to start with.
You haven’t mentioned how “hopped up” the old Caddy is. Big cam? High compression? If it’s mostly stock with a mild cam, it should idle down at least to 650-700 rpm. I think you have an air leak somewhere if it won’t idle below 1000 rpm.

 

Just waiting to get hold of a vacuum gauge and see what it tells us.
The engine has a mild grind on the cam and has later year heads which improve compression slightly.
The philosophy behind the engine build was just to gain a little efficiency with fuel, ignition (HEI) and exhaust.
I like mostly stock stuff for reliablity.
I reduced the displacement from 346 (150hp) to 322 (125hp) as I was led to believe the smaller bore was more rev friendly and with improvements I'd probably be up around 150hp anyway.
For a old style hot rod with a flathead engine giving out 150hp, I felt I'd be happy with that.

I do thank you and others for your broader comments and feel that I may need to take on board the need to have both carbs running together full time.

 

In a 2x2 setup, for BEST performance at idle, BOTH carburetors should run together, NOT progressive, due to an imbalance of fuel distribution to the cylinders if running progressive.

Driveability will also be better (although in the light body you have, probably not an issue) at all conditions other than wide open throttle.

Jon

 

Thanks for sharing all the knowledge.
This carb stuff is something I have not indulged in at all.
I can see why now.
Much easier though with good help and recommendations...

 

Look at the picture El Scotto shows with the two circles around the idle stop screws. The front carb has the choke and linkage plus the fast idle cam, the rear carburetor is missing all that. The idle screw is not working as it should be ( the rear carburetor idle screw is bottomed out ). Both carbs need to be identical in every way or you are just fighting a loosing battle. Take the back carburetor off and block the intake. If the front one will let the engine idle and rev up, then switch them and get the second one to do the same. Both should be able to idle the engine on their own with the second opening blocked off, once together, some fine adjustments will be needed. UNHOOK all external vacuum lines and plug the holes while trying to get it to idle down.

 

Russ - most of the information in the link below is applicable to your application; if you subs***ute the words "2-barrel" for "1 barrel", and "V-8" for"6".

Note the section on synchronization.

https://www.thecarburetorshop.com/Dual1barrelcarbs.htm

Jon.

 

I have not had the time to read the link above, but will definitely take the time to do so.
I have come to better understand what you are saying about running both carbs full time.
So, with that in mind I'd prefer to correct what I have and proceed in that new direction.

Where I am is not easy to get help or source 2GC stuff especially for hot rod purposes.
I did however score a bulk lot of stuff from a guy in CA about 3 years ago and just bought it cos I could and not being a carby guy I did not know exactly what I had or was getting.
Just seemed like a good idea at the time.

That is where I got the replacement base from with the air mix screws I think.
Anyway, I have gone back in my shop and found where I stashed this stuff and have found a similar base also with adjuster screws which maybe what we are looking for to run both carbs full time.

I have taken a couple of pic's to see what you guys think.
The orange one is the one I removed previously to add the screw adjuster base, while the black base is one I've just found in my stash which could be what we are looking for as it does have adjuster screws and become my new 2nd carb.

At a first look, if this new base will work, I see that I lose a small vacuum port but probably no big deal and see that adjusting those rear carb screws maybe fun...

In the meantime, I will proceed and make a block off plate so I can setup my engine running just on the front carb as suggested.
Does that sound like we are on the right track now???

 

Beyond the base plate issue, there is still the question of what the carb (secondary) looks like inside. Can you open it up and take a pic of fuel bowl area and the bottom of the top plate. Typically, mods must be done to block off areas in the carb so it plays right as a secondary. These mods, if done, will interfere with the normal operation of the carb.
In addition, check for wear play in the throttle shaft bushings of those bases. Sloppy shafts leak air. Oversize shafts are available as are the reamers to size them correctly for the new shafts.

 

I don’t have any knowledge of these carbs, but I know that when I ‘balanced’ my fixed linkage - twin two barrels on sbc the idle came down considerably.
I do not have enough knowledge to understand why, (and unless I missed it) no one else has mentioned balancing both carbs, so my point may be pointless.
Once you have the identical parts issue sorted and if running fixed linkage as others have recommended, maybe it is something to consider……

 

Yes, given a little time I can pull that other (secondary) carb off and take pics as you suggest.
I'll make the block off cover first, which save from any accidental dropping stuff into the opening.
Right now I am not feeling lucky, I am recovering from a bad Covid 3rd jab which put me in hospital for 5 days.
I am improved now and recovering well but slowly.
Problem is you get what is called a foggy head' where the old mental function kinder works in slow motion, so I am being real cautious right now about doing anything stupid.

 

A little light humour while waiting for me.

 

good advice to yourself for what you have been through……

 

good info here while you are taking a break
Hot Rods - My turn to start a Rochester 2G thread I guess... | The H.A.M.B. (jalopyjournal.com)

 

Sorry for the delay in posting my reply.
As you can see from the attached, I removed the secondary carb and blanked off the manifold.
I had a lot of trouble starting the engine which I now believe is related to a cold start.
I note that the choke ****erfly in the top of the carb can not function as it clashes with the bridge that is there to screw the air cleaner to.
I can not see how that coiuld evcr work right!!!

The only way I eventually got the engine to start was by holding a bunched up rag over the opening for a couple of seconds while cranking the engine.

Once started and warmed up, by controlling the throttle linkage by hand, I could eventually get the engine to run on the primary carb at an idle speed of about 750rpm.

What is next???

 

Hey Russ
have no carb advice for you but HAPPY BIRTHDAY!
Dan & Lucy

 

That air cleaner boss looks like it was added to the carb neck?

This looks like what I remember of casting boss for air filter being above the choke ****erfly

 

Looks like it's time to pick up a carb core or two and couple kits and go thru the carbs yourself, they are pretty simple carbs, and put together a primary with either a manual or the earlier style auto choke (the one you have was made to work with stove on the manifold). Once you get that done and running; build your secondary carb.

Can't see in any of your pictures if you have the 1/8" npt vacuum port plugged on the right side of the carbs.

 

Here is the base of the secondary carb that I removed to block off the manifold opening.
I note, that has a different air cleaner bridge support.
In my case I am not using those bridges as I am clamping my air cleaners around the uper neck with a radiator hose style clamp.

 

Thanks Dan another year older and here is hoping wiser as well.
Hope to catch up soon buddy.

 

Yes, I think you are right, as looking at the other secondary carb it looks more like what you have posted.
Starting to think I was done over on this deal...

 

Now that I've had time to digest some of the comments and the situation I appear to be in, maybe it would be better to see what I can salvage from what I have and then just buy in what is needed to fill the gaps.

I know that I am out of my pay rate here with carbs, but since it was suggested that I run a pair of full time carbs, which I accept is logical, what do I do next.
From what I can gleen off a quick surf of 2GC carb stuff, should I be looking for only 2G carbs with say a 250 cfm or there about???
The engine is 322 cubic inches.

First other question is, can I use any of the bases I have, I'm guessing yes, so then the next question is what do I put on top of this pair of bases???

 

Maybe you could swap the top off one of the end carbs onto the middle carb and stick the choke plate into it.

 

It is not a tripower, it is a twin carb setup.

 

Will make one more post in this thread.

Would highly suggest that you start from scratch, rather than trying to build on what you have. I show 708 listings in my database for Rochester 2G, 2GV, and 2GC series carburetors. Rochester did not build that many different carburetors just for the exercise. IN MOST CASES, CASTINGS ARE NOT INTERCHANGABLE!

What you currently have are "Frankencarbs".

Yes, I am quite aware this is a hot rod forum, and any good hotrodder with a lathe, a milling machine, a welder, and a few other specialized tools can make almost anything work on almost anything. But how many own a lathe, a milling machine, etc.?

Often, and especially in this case, simply easier to start with something that requires little, or even no, modifications.

If you are in love with the Rochester 2G series(opinion - they are a great carburetor), then find two from 1955 to 1967 that are identical by tag number; or find two 1968 and newer that are identical by bowl STAMP (not casting).

Other options would be two of the exact matching Stromberg WW series, all of which have a stamped identification number; or if I were doing this (I read in the first post this was a Cadillac engine, ***ume this has not changed), I would use two of the Carter type WCD carbs identification 595s original to the Cadillac, and the carburetor of choice for the early 2 x 2 setups on Caddy engines.

Right now, adding to what you have is (opinion) what my Dad used to say was throwing good money after bad!

A 2 x 2 on that engine is one of the easiest of all aftermarket multicarb setups. Just don't make it more difficult than it should be!

Jon

 

Here is a breakout of a 2GC for reference if you do not have one.
And, there are some Carters over on that auction site if you wish to look at them.

 

OK, one additional post:

USE THE EXPLODED VIEW ABOVE CAUTIOUSLY!

This is one of the "one size fits all, is correct for none", probably done by someone who has never seen a carburetor. Note that there is both a choke pull off (used on the 2-GV series) AND an integral choke (used on the 2-GC series).

Rochester NEVER made a carburetor that is exactly like that picture!

Jon

 

Need to pay better attention.