Hot Rods Rochester 2GC Small Base Carb Help

I am no carby guy, so you will need to be patient with me.
The story is as many would know I have a 1926 Model T with Cadillac flathead engine which a Burrell twin carb manifold.
Life has gotten in the way of me completing this project but I have not given up and I am very close to the finish line now.

I purchased a pair of carbs from a so called expert in TX some years ago.
Never did get around to studying them closely.

Several years later I installed them and eventually tried to get the engine running, which it would do but not idle.
It can be seen ruuning in my YouTube video.

I never gave it much thought initially, but later when I attempted to get it to idle I discovered neither base plates came with an idle adjustment in them.

That seemed wrong, so sometime later I scored a base plate with the adjust in it.
Now, I have a setup that wont run at all and I figure it is time to ask the audience what do I need to do to get the darn thing to run and idle.

The front carb is the idle carb simply for ease of access to the adjustment screw.
Picture attached.

 

I couldn't tell by the images, but if they are large base 2G's, like came on Pontiac tri powers, etc., with no idle screws, the odds are they are the end carbs for a tri power setup. No mod will ever get them to run as a single carb as far as idle, etc. Your best bet is to find or buy the big base rebuilts set up for standard carb performance (with idle screws).

 

That is a good possibility but the front carb has a choke pulloff on it, the rear doesn't. Do either carb have choke plates? If so, they aren't from a 3X2 setup. It sounds like the carbs are pieced together to me.

 

I am NOT familiar with the Burrell intake.

Having said that, the old Detroit Racing Co. intakes were set up for a pair of Carter WCD carbs. The normal set-up was to use the original carb, and acquire another EXACT matching carb. Common were the Carter 595s used on 1946~1948 Cadillac engines.

Do you have any documentation from the original seller denoting what carburetors you purchased?

The WCD Carters are the smaller common base, not the larger base.

The side inlets like in your picture are common to many small Chevrolet engines.

When using a 2x2 set-up, such as yours, best results will be obtained by using two MATCHED carburetors, BOTH with idle circuits (unless it is a trailered race car, and no idle is desired), and running solid linkage.

Switching throttle bodies on Carter, Rochester, Stromberg, or Zenith carbs is, at best, a crap shoot, with loaded dice (I am not expert with either Autolite or Holley, so no comment on these).

I know the following is NOT what you want to hear, BUT:

In my opinion, trying to do anything with what you have is throwing good money after bad! Take the carbs off and replace with MATCHED carbs the proper size for the engine.

I, and I am certain others here, will be happy to help (see last paragraph for caviat); but any of us are going to need more information.

We need engine displacement (the 595s was used on a flathead 346 CID, but I don't know if that was the only displacement for flat head Caddys), a "picture" (either word or actual) with measurements of the intake carburetor footprint. Common measurement would be center to center on mounting bolts both side to side and front to rear.

Engine modifications, if any, would be nice to know; such as different camshaft, downgrade to an electronic distributor WITHOUT upgrading to an alternator, headers, etc.

Either post here, or will be happy to take your telephone call: 573-392-7378 (9-12, 1-4 Mon-Tues central time).

And no offense, if you have downgraded to the electronic distributor without upgrading to an alternator, my offer is void, other than to tell you we did several sets of the Carter 595s WCD's on the Detroit intakes, always with happy customers.

Jon.

 

What I will do is get a couple of close up pic's and post them here of the current setup with carby bases that you guys can eyeball.
I am not at my shop right now so it will happen in about 8 hours time.

 

Prob. good advice on just forgetting the current ones you have and go with a matched set that belongs on your setup. Multiple setups ain't cheap and they never bolt on and forget like a single carb. Potential future problem areas will include the linkage, a fuel regulator, vacuum leaks, flooding, and other little nasty's that are just part of it. It only takes $$, a lot of time--and some hair.

 

One other comment:

If the carbs came with bases that have no idle adjustment; it is probable that there is NO IDLE CIRCUIT in the carburetor.

Changing to a throttle body with idle adjustment would not add the idle circuit, only add a vacuum leak.

If anything, this would make the idle worse.

Jon.

 

Those carburetors came with brass or aluminum ID tags mounted on one of the top screws, be sure to get the tag numbers in the picture when you post more photos. That's the key to identifying what you have whether you end up using them or not.

 

Just to take a step back and put things into perspective.
The carbs that I got from TX were rebuilt and seemed to be as described etc.
The only issue was that this guy sent me both carbs with the same base plate, which meant I had no base plate with idle adjustment screws.

Even with those two carbs the engine would run fine but not idle obviously.
Being a dumb ass when it comes to carbs, the penny did not drop right away that I needed idle adjustment screwed base.

I acquired the correct base also new rebuilt from Charlie Price (who I was unaware of earlier - nice guy and very helpful.) Upon receiving the idle screw adjuster base, I tried to run the engine and now it wont idle or run.

I'm assuming I need some hints/procedure as to how to setup the adjustment screws to get the engine to run from scratch so to speak...

Surely I am close!!!

 

On the plus side, if those carbs are indeed end carbs from a tri-power setup they are sought after and worth some good money.

John

 

Those photos show idle speed screws and air mixture screws, so what is missing ?

 

The knowing how to set them up for the engine to run.
Simple I'm sure for those who know.
Just that I'm a dumb ass when it comes to such carby matters...

 

Hard to say just what is there. The throttle arms on both carburetors are as fitted to a normal 2 bbl, or the primary carb on a tri-power setup.
The secondary carbs have a smaller link on the passenger side with a rod to connect them.

 

@carbking touched on that in post #7, there may not be idle circuits in the carbs.
Try to screw the adjusters in, easy does it, just seat them. Now back them out 1 1/2 turns and see if that helps the idle circuit become effective. If the engine does respond then adjust to suit.
And there’s another thing to check, there may be a secondary carburetor gasket in that front carb blocking off the idle circuit.

 

OK, I will start with the screws all the way in and the out 1.5 turns.
Gotta start somewhere...
I'll be back.

 

OK, did the screw adjustment, had a little trouble getting started, probably cos it was a cold start.
Played a little with the choke and it fired up.
I think I am screwed in about 1.25 turns.

Right now, it will start and idle at about 1,000rpm.
I can not seem to get it to want to run much slower.
Should I now be looking at timing???

 

Fordors nailed it. Those look like typical Chevy primary carburetors. As mentioned, real secondary carbs have small levers. So the carb body should have the necessary idle circuits in the main body. Check to see if the base to body gasket is blocking any passages and while the base is off, check to see if the builder installed plugs in there somewhere. Post pictures of the bottom of the body and the top of the base.
You should get another base with the idle circuits so that both carburetors are identical. Hang in there, it should be ok with a little tinkering.

 

Its Friday morning where I am and my birthday to boot, so even getting to this stage is a great start to the day.
I will take the carbs off over the weekend and post some more pics.
Mucho gracias amigo's

Be back tomorrow.

 

Before you take the carbs apart for pictures try some fine adjustments. If you have a vacuum gauge adjust for the highest reading, if not then adjust for the highest idle, and naturally you want to trim the idle speed to what you find acceptable.
If you can’t get the engine to respond to those steps then it’s time for Jon’s
( @carbking ) expertise.

 

See below.

 

Great, thanks for the tips.
Does that include playing with timing now???
These Cadillac flatheads are famously known for their slow quiet idle so at 1000rpm for now,
I've a got a ways to go...

 

Just wondering why you want it much slower than 1k idle. My bone stock truck motor with 3x2 (avatar) idles o.k. at 900 but 1k even better-especially if i turn on the a/c. Any lower and it has tendencies to die in turns, quick stops, etc.

 

Does this mean the engine dies if you lower the idle speed any further? Or does it mean you can back the idle screw out further but the rpm's don't drop below this rpm?

 

Mostly form what I had heard about these engines but upto now I dont have the option/choice and feel that there is probably a little less available.
However you are probably right about the rpm.
I'm just feeling my way right now.
That is why I mentioned timing as a means to slow it down just a tad more in the first instance.
More trial and error, but vacuum could be my friend as mentioned by Fordors in this case.
Trying to borrow a vacuum guage for now...

 

You are attempting to get stock performance (idle, etc.) out of a modified engine--rarely, if ever, works-for anyone. Modified beasts are set up the best way to gain performance normally, there are trade offs that you must make for that however.
Stock performance=stock engine.

 

This may or may not be of any value but it has been suggested on other carb adjusting threads that you should be adjusting the carbs with the linkage disconnected FWIW.

 

Both carburetors SHOULD have idle adjustment for a better idle.

Jon

 

Is that a thermal valve (I may not be calling by proper name) (used on California carbs) I see on the back of the front carb? These types of carb body's have a circuit that goes down to throttle plate body cavity to pull air in and lean mixture out.

 

^^^^^ Ok, it's called a idle compensator valve. Shown on page 3 as parts 61 60 59 58 57 of diagram per Mikes link https://www.carburetor-parts.com/assets/instructionsheets/K636.pdf

 

Whats going on here?



The idle adjuster screws are not screwed in near the same and the idle cam appears missing/mis-oriented on the right carb.