Rochester Carb Adjustment

[Keller]

Originally Posted by charlief1

The link didn't work for some reason.

A shortened link was copied from another site, methinks.

Please post the original link.

[Keller]

Originally Posted by jjurva

What was that tube for?

It is used to generate hot air that will heat the choke up and put it at the right place as the car warms up.

At least it does on my Carter AFB...

[jjurva]

So where should it be hooked up to? I ran some car cleaner through it and the carb cleaner comes out of these little holes on the wall next to the throtte plates. I have a manual choke so could I just plug it. For some reason I am not getting enough gas. The engine will run when choked but will only run for a little while if it is not.

[chrisjkruse]

I believe that you are talking about the vacuum port for the vaccuum break diaphragm. Its part of the choke system that locks the choke linkage. It works in conjunction with the heated choke coil spring You probably do not have this anymore. Its a big diaphragm on the side of the carb.
If you have a manual choke, then cap this vaccuum port.
Cap all of the unused vaccuum ports.
AND don't forget the RAG trick.

[jjurva]

It still will not run if not choked. It will run for like 10 seconds then die but if im under the hood i can keep it running by choking it with my hand. So its just not getting enough gas when not choked right? how can i fix this? I took the carb took it apart and cleaned it

[chrisjkruse]

Yes, you are not getting enough fuel at idle. All fuel enters the engine by the manifold vaccuum and the velocity of the air creating a low pressure (venturi effect) which draws the fuel thru the jets. (except when the throttle is opened quickly, then there is a piston that squirts fuel down the throat of the carb to compensate for the momentary vaccuum drop that takes place)
There are idle jets at the bottom of the carb which are smaller and are the first jets to operate . More air speed/volume is required to draw fuel from the larger/higher jets above these.
By choking off the air flow you are forcing more fuel into the carb-(Not from the venturi effect-but rather like sucking on a straw.) Fuel will enter thru all of the jets.
My guesses are:

A. The idle jets are clogged
B. There is not enough vaccuum to operate the carb effectively.
1.( you mentioned something about vaccuum advance.) Make sure that your ignition timing is correct.(there probably is a vaccuum advance)
2. Make sure that there are no more vaccuum leaks.
3. Check that the timing chain has not jumped a few teeth.
4. Satisfy yourself that the carb gaskets are in good shape( both within the carb and where it mounts to the manifold. Also the intake manifold gaskets.
5.Do a compression test to determine if there are valve, head ,or head gasket problems. ( If it can't compress..than it cant suck either!) i should get a t-shirt with this on it.

[chrisjkruse]

I have never checked for vaccuum leaks with carb cleaner, but some people have suggested it to me. I"m allergic to fireballs!
But, If you convince someone else to spray carb cleaner(not starting fluid) with the hose.. along the outside of the carb, vaccuum lines, and intake manifold gaskests while the engine is running He Or She can report back to you if there was a momentary increase in idle speed. If so, then ask that Heroic Person at what location was He OR She spraying when the idle increased. Assuming that there is no fire and communication has not been disrupted, the location that was sprayed which increased the idle is the location of your vaccuum leak.

[charlief1]

Well here's a better pic for you of a blown up one, but I don't know how well it'll work. I'm also including some links that may be able to help.

http://www.carbkitsource.com/carbs/t...Jet-index.html

http://www.tocmp.com/manuals/Carbs/R...nual/index.htm

[chrisjkruse]

Charlie,
That's cool! 1964 manual with everything you need to know...Even adjusting a "six pack" on page 17. Good history lesson for sure!
Chris

[charlief1]

I figured out it might help some since it sounds like he's got an old 225 engine instead of the later 231.