Chevy 4bbl 350 SB rochester

Hello guys, I have a serious problem with my carburetor.

I have recently restored a boat "Boesch 510" (swiss built waterski boat in mahagony) from 1971 with a chevy 350 engine named Crusader 220 with a rochester 4 jet carburator but i have a problem that it only runs for about 30 sec before it stops, takes less time on higher rews, but if I give some throttle whilest it is about to die it kicks back up again, because the acceleration pump gives it an extra boost of gas. Then it just repeats, slowly going towards a standstill and i have to give it some gas with acceleration pump agian.
I think its because it doesnt get enough gas, i could have accepted this fact if it only happened on idle drive, but as i said it happens on higher rews to.
it might be slightly plugged injection.??? will be checked this weekend..
Have anybody any manuals for this type of carburetors, as I want to tune it to perfection or at least get to run smoothly ( I want the good "mumble" from a 350 out of the pipes)
A manual would be wonderful because things like this might happen again in the future so its more of a precaution. Although any tips would be really nice considering i've done everything i can think of.. We have already taken the carburetor apart once but it might have plugged after that, i cant really tell, but when i blow in the "full throttle" pipes, the 2 up front, it drops down gas, but when i do the same, or blow allot harder in the back once i cant see any evidence of any gas making its way down, are they lower set than the top 2? Have anyone had any similar experiences? The interesting thing about it is that when i start her back up after she has died i don't have to give any throttle it just kicks back up and there is of course not any auto choke. So that tells me that it gets gas somewhere but not enough? Or it vaporizes? I have no clues to go on, or i might have but i cant make any since of them. So, please, Help!

Ignition is timed and works well, it is only a fuel problem.


Best Regards, Per and Erik Sundblad in Gothenburg, Sweden

Have you checked the fuel pump?

Also there is a filter in the carb inlet fitting that is commonly overlooked, if clogged that is what will happen, as you describe.

hmm, the fuel pump works fine, I've checked that..

I haven't checked this filter but if it was clogged it wouldn't run on the acceleration pump because that one sucks gas thru the same pipe. So I don't think that is the problem either. :S Its really strange, i will check the filter to, I'll get back when that's done but i don't think its the problem. Any other ideas? I really need to get this worked out because the summer is well on its way and my boat is in the garage.. :(

Not so fast, buckweat. Listen to the guys who have been doing this for a while! First, how did you check the fuel pump, with a pressure gauge? Were you able to get the engine running at a running RPM (say, 2000-3000) long enough for you to get an 'at speed' reading? Did it ever drop below 3-6 PSI?

Now, for Maxwedge's suggestion. The accelerator pump well sits pretty low in the carb, the bottom of which is below the bottom of the float bowl. Since gasoline flows downhill, a restriction in fuel flow will allow the jets to be uncovered from time to time (which results in fuel starvation), while the accelerator pump well has enough fuel in it to give a nice 'squirt'.

Maxwedge, thank you for the suggestion as I had completely forgotten about the filter! I've had that filter plug once on my current car and it resulted in exactly this running condition.

If the filter checks out, make sure it isn't flooding instead of going lean. Flooding could create similar symptoms, including the easy restart, and opening the throttle would admit additional air to relieve the flooding condition.