Hot Rods Running problem 350 sbc

I am having major running problems with my 350 sbc with a 2 jet Rochester carb. The car was running fine once it warmed up but now it will not idle, it stumbles and when driving down the road and you take your foot off the accelerator it dies out. My first thought is fuel related. I tested the mechanical fuel pump pressure and I am getting 5.5 pounds, which I think is O.K.. Do you think it could need a carb rebuild? I did not perform a compression test as like I said ,it was running ok up until now. I have only owned the car for a short while and really havent driven it much. It may have sat around for awhile before I purchased it.
This engine is in my 1947 Chevy and I am not positive what year the 350 sbc or carb came from. I called all the local auto parts stores and unless you tell them an exact application they have no idea how to get me a Rochester 2 jet carb kit.
Any help is appreciated.

 

sounds like a vacuum leak-hose pull off or crack?carb base gasket?good luck

 

could be **** in the carb. You running a filter?

 

Sounds like its time for a tune up man.

 

I know this isnt an exact science but to check for a vacuum leak I put my hand over the top of the carb and the car died out. If it had a vacuum leak It would have kept running, but rougher.
There is an inline fuel filter and possibly one in the carb.
All tune up parts appear to be newer.

 

old gas? or fresh?

 

Here's a good thread that talks about some possible issues with the 2 jet Rochester carb....Might be of some help.

http://www.jalopyjournal.com/forum/...hester-2-barrel-float-needle-sticking.718828/

 

Actually, it may be time to apply a little more science.

Does it have a working choke? Manual or automatic choke? Is the choke fully open at operating temperature? Does the choke pull-off work? Are the carb mounting bolts tight? Have you checked the manifold vacuum? How many inches?

What's the initial timing set at? Is the distributor tightened down? Does the vacuum advance work properly? Does the exhaust smell rich or make your eyes water?

If you partially blocked the carb with your hand and it dies then it means it didn't like being richened up. Try pulling a vacuum hose off and see if it likes being leaned out.

 

This is NOT how you check for a vacuum leak

 

Could be bad gas or something in the tank. A good filter should keep the junk out of the carb but the liquid they call gasoline these days isn't always good for the older carbs. The carbs have a tag on them but many people don't put them back on. Does it have points or electronic ignition. If the key is on without the engine running the points can burn and cause rough running. You could have a fouled spark plug.

 

Since the car has never run correctly while you have owned it. I would suggest pulling the tank, getting it clean, replacing the sock on the pickup and any fuel filters, check the line carefully and be sure it's not crushed anywhere. Blow out the fuel lines, replace any rubber line with fuel injection line that will stand up to ethanol blend gas. rebuild the carb.
None of this is high buck, just time and labor. Eliminate some variables.

Once you have a good fuel system, start tuning.

 

The 2GC is probably the easiest carb to rebuild. ID is pretty easy and can narrow it down a bit. The '55 to '67 models had the tag, '68 and up had the ID numbers on the side of the fuel bowl towards the front on the p***enger side.

 

The idle circuits are plugged or have water in them. Take the idle screws out and squirt some carb cleaner through it. Put them back in and bottom them out by hand and back them out to about 1 1/2 to 2 turns out. See if it runs better.

 

I bought a carb kit today but unfortunately it must have been wrong as the needle valve seat threads were larger than the original. I did take the whole carb apart and cleaned everything out and reused the old parts as they appeared brand new. I also replaced the internal filter and dis***embled and cleaned out the inline fuel filter. I am beginning to think that one of the fuel hoses is falling apart as there was black crud in the inline filter. I was only able to start the car in the garage as it was raining out and the car has no working wipers. The car did run better at least just sitting there idling. I will let you know how she does on the road. Thank you for all the help.

 

Does it have a heat riser in the exhaust manifold? Is it working?

 

To set my mixture screws I turn them out one at a time until I get my best reading on my vacuum gauge and then I turn them back in a 1/4 of a turn. I was surprised that they are out almost 5 full turns to get the best reading.

 

Could be hoses, or could be crud from the tank. Better find the source of it, either way. You don't want a plugged filter, or a burst fuel hose.

 

5 turns out is too much. Something is still plugged. While you have it apart, blow it out with compressed air (idle circuit).

 

Montana1, I agree 5 turns out seems too much to me also. That is about how many turns out there were when I bought the car. I did blow out every orifice I could find when I had the carb apart. In which section of the carb is the idle circuit, the air horn, float bowl or the throttle plate? I'm guessing the lowest section the throttle plate?

 

This shows the layout of the idle circuit... The lower idle air bleed look to be pretty well concealed.

https://www.carburetor-parts.com/2-Jet-Idle-Circuit_ep_656.html

 

Claymart, thanks for the diagram.

 

'Tis a thing of beauty, ain't it? Lots of other good diagrams on that site too...

 

It's hard not picturing klink trying to figure this out

 

You said it "was running fine". What did you do since then? Often the last thing we did or "adjustment" we made is the culprit.

 

Try pulling the idle mixture screws and then spraying some good carb cleaner down through the idle air bleeds in the air horn. Sometimes a bit of crud gets stuck in those p***ageways or on the air bleed hole in the air horn it's self.

 

If it is a 350 then the carb kit for a '76 Truck will work unless someone put an early carb on it. That would be the bigger one and most kits will work on either. but if you tell them '76 Pickup you should be just fine with it.

It could be something as simple as a vacuum leak so first check for that but it never hurts to freshen the carb on a car of unknown pedigree anyway if you are planning on driving it.

 

I took the carb apart again and blew compressed air through every orifice along with running a wire (Extra thin)through them and carb spray. The car is running better than ever now but as I stated in an earlier post the adjusting screws are out about 4-5 turns with a 17-18 inches of mercury on the vacuum gauge. I don't think it is running 100% yet but it is a step in the right direction. It seems to be idling OK.

 

I had one of those 2bbl. on a 70's wagon one time and the thing had two different size holes in the needle jet orifices. One was out about 5 turns and the other was at 2 turns.

I unscrewed the jet needles and got out my # drill bits and opened the one that had to be out 5 turns a couple of thousandths, and that thing ran perfect! I don't remember how big they were though, it was about 30 years ago.

I almost always find myself re-inventing the wheel!

 

Answer the question if you want help.

 

I had a 2GC many years ago on a '65 C30 truck.. nothing but trouble. Parts store had new ones for a reasonable price, so I went with that. See how much they are just as an option.