The Stovebolt Site Forums The Shop Area Engine Shop Carb Flooding....

It seems that even brand new carbs when setting after running they internally leak. I have had rebuilt and brand new ones and all of them leak internally. Is it the gas? Perhaps something else. I have rebuilt carbs for over four decades and still running into the same problem. Starts right up first thing then when set, it takes several engine turns to restart the engine. Any ideas? Frustrating! Do I need a fuel pressure regulator or adjust the floats again. I live at 1300' above sea level.

I would check the choke adjustment: too tight or too loose. Even a warm engine can benefit from a small amount of choke. Too little may not be noticable except by needing a few more revolutions to start; too much could give the same result, although black smoke after starting would be a strong indicator of too much choke. Fuel volatility can also be a factor if the condition mostly occurs during warm/hot weather. If that is the case, there isn't much you can do about it, because fuel blends are pretty strongly regulated in most areas.

Harvester

What kind of carb are we talkin' bout here Henry, what year, is it a Chevy truck????
Denny Graham
Sandwich, IL

Any time a carb floods after it is shut off fuel has to be getting by the needle & seat. It's like the tank in the toilet. When the bowl fills up the valve shuts off. If it doesn't it run s over into the stool. Dirt in the needle & seat is the most common cause. It could be a float set too high or hanging on the side. It could be to much fuel pressure. It can be a float that is soaked up with gas or has gas leaking into the pontoon.

Ya left one scenario out George; it could be an early flat top Rochester 'B'!!!
I understand and appreciate your logical approach to the problem, that’s the way I would have assessed it. But if it’s a ‘B’ then logic doesn’t seem to apply and I’ll be damned if I can figure out why. Many more knowledgeable than I about carburetion have come to the same conclusion about the Rochester ‘B’ and some expert shops won’t even service one.

Take my ‘B’ for instance!
I'm running a factory stock set up with a stock single stage fuel pump, it might even be the original, so I’m sure that it’s not putting out more pressure than the N&S can handle. For it to put out more pressure than it was designed for would be illogical. Generally this condition only exists when an after market high-performance mechanical or electric pump is installed. In addition to the glass bowl filter/screen on my pump, I have an AC sediment filter about 10" up stream of the carb which catches any fines that might get through the screen.

The floats are brand new (no leaks) it is meticulously set for balance, fuel level and side clearances. The N&S are brand new, and of course it is a Viton needle, aren’t they all now days, it’s not sticking, worn or damaged in any way and it has no dirt/debris/obstruction under it.

The mating surfaces of the air horn and bowl are parallel and the gaskets are new. They were stress relieved on a specially designed fixture to hold them flat with in a few tenths and then machined flat in a Bridgeport mill while bolted in their normal position.
This carb was completely gone through a couple of thousand miles ago. When I say completely I mean the lead plugs were pulled and all the passages cleaned to assure that there was nothing in them and new lead plugs tapped in.
I just had it apart a couple of weeks ago to check for any dirt or something, anything inside and all looks clean and exactly as it should be.
The power piston is free sliding in the well but not loose, it is straight and contacts the ball check smack dab in the middle, the bias spring is the right length according to the specs and not bent, rusty or deformed. The main-well has the correct gasket under it. This is an area that I often find improperly serviced. The kits usually offer a couple of choices of gaskets and quite often the wrong choice is made by the installation of the wrong gasket. This causes the main well to be cocked and misaligned with the power piston. During the tune-up, the idle screw was backed out about 1 1/4 turns for it’s final setting. The vacuum gauge was maxed out and steady at around 20 in.hg at idle.

This engine will start the first turn over by tapping the accelerator once when cold. Once it is warmed up and you shut her down it will start on the first turn without touching the throttle, that is within 5 or 10 minutes after you shut her down. If you let it set for a half hour or so it takes a minute or two to get it cleared out, acts like someone had been stomping on the accelerator and has it flooded. When I take it out for a run of say forty-five minutes or an hour she runs along just fine. Then when I pull up to a light after cruising along at 2500rpm the engine is running rough like the choke was pulled half way out. It clears up as soon as I take off again. I’m about 99% convinced that the problems with the ‘B’ are heat related but just can’t put my finger on the why.

If you have ever worked on is predecessor the Carter W-1 you can understand the need for a carb that was easier to service. It is the opinion of many that although the Carter carburetor was more difficult to service it was a much better performing and more dependable carburetor.
The whole concept behind the ‘B’ was to create a carburetor that was trouble free and easy to service. This is about the simplest carburetor that I have worked on and maybe that is the reason it has such poor performance, it’s just too simple. The addition of two or three more screws on the air horn would have solved many of the problems that it has. However the fact that GM persisted with this basic design for more than a decade shows you just how much confidence their engineers had in it. Or perhaps it was the bean-counters that just wanted to cover the cost of adding the Rochester/GM carburetor to their lineup.
I hate to do this but I’m now in the process of refitting a W-1 to my 1950, 216 to see if all that I’ve heard about them is true. This is gonna take a few days since I will have to make another set of fuel and vacuum lines for the Carter.
Denny Graham
Sandwich, IL

Yes, I left out the heat factor. Some use a thick plastic spacer under the carb. Did you check the pump pressure? Ive been reading in these posts that guys have excess pressure from the pump that is supposed to match the application.

Think we might have lost HenryG guys or maybe he found the secret and is gonna keep it to his self.
Anyway George, if you’re talking at me, sure, the set up is absolutely stock, bakelite spacer and all, just like the day it left the factory. Taint bothered to check the fuel pressure, it’s been running like this for more than 20 years that I now of for sure. That’s based on my research, which took me back to the previous custodians that maintained the truck for the last couple of decades.
And once again, there just isn’t any possibility of the pressure going up with a stock AC mechanical fuel pump. There is only one direction that it’s a gonna go and it taint up.
Denny Graham
Sandwich, IL

Where is carb king when you need him?
I also think the heat is a factor, but it is a factor because of today's gas.
Denny
The original Rochester B was on my 292 for many years before switching to a Carter AVS 4BBL, four years ago. I never had the problem you are having, but even so, I still think it's the gas.
I am trying to reacquaint myself with the Carter YH side-draft used on '62-'66 turbo Corvairs. They very often have a serious problem with hot restarts, with gas running out of the carb (remember it's a side-draft) and dripping from the air cleaner. There are a number of potential problem areas, inside the carb that can cause this, but after the carbs are made perfect, there are two other things that most guys have to do to stop the dripping. They have to lower the float level 1/16 - 1/8" below specs. The fuel pressure, even with a stock pump has to be regulated to about 2-3psi. The float levels and pump pressures that worked in the '60s, just don’t work on these carbs today.
I talked to a guy at a show with a '54 Vette, that uses the Carter YH on the 235. He said it's common knowledge among the other early Vette owners that they have to set the float 1/8" below original setting, on all three carbs. What worked in '54, doesn't work today, however they are able to use the original fuel pump without a regulator.
I'd say try your "B" with a lower float level (higher when measuring from the gasket, UP to the bottom of the float). I'd also check the pump pressure. It may be all stock original, but it may be more than the carb can handle with todays gas.
You mentioned a "B" in your other post that didn't have an idle (bowl) vent. Were you saying yours did or didn't have the vent? According to an old rebuild sheet I have, the Rochester "BC" didn't have a vent, but the "B" and the "BV" did. Or at least, only those two have an adjustment for it.


Henry
You didn't say what carb you have, but to answer your question, YES, I think you are correct about float level and fuel pressure.

Richard - the YH carbs have a couple of issues that are not the fault of the carburetor:

(A) There are 4 distinct generations of the YH: (1) Corvette and early Nash; (2) marine applications 1956~1959; (3) marine applications 1960~1964 and turbo Corvair 1961~mid-1964; (4) applications mid-1964 and newer. EACH GENERATION HAS A DIFFERENT BOWL COVER GASKET. The generic commercial kit has two gaskets.

(B) Carter used spring-loaded needles and seats in the YH carbs to minimize flooding issues. Spring-loaded fuel valves cost approximately 8 times the cost of the solid fuel valve. Guess which valve is in the generic parts store kit.

The major issue with the YH is the diaphragm-type accelerator pump. There is no neopreme yet known to man that will survive deathanol and drying out. Those who drive the cars daily should see 2~3 years without having to rebuild the carbs. Those who drive them and then let the fuel evaporate from the bowl can expect to rebuild about every other time they start the engine.

Jon.

Hey Jon, lets talk Viton. All of the needles I've seen in the last 40 or more years have been Viton. How does this hold up against the alcoholic gas? Do you ever encounter problems with them?

Richard, mine is the flat top 'B' or the first versions, which were introduced in '50. Apparently by the end of the following year they were already having problems with them and they were beefing up the castings and many more changes were made over the next decade.
No venting of the bowl in the early ones. There is a check valve in the plunger that is supposed to allow the gas that percolates in the well to vent back into the bowl rather than into the venturi and drain into the manifold but that was it for the early 'B'.

And the biggest problem I'm seeing with this engine is after its shut down, the fuel pump pressure would have nothing to do with this after the engine is shut down. After a 20mile run at highway speed we shut her down and were watching the AC sediment filter. Its is a few inches in front of the carb and we watched it drain over the next 15 minutes and the glass bowl on top of the fuel pump also drained down about half way or about even with the screen. Why these drained down has me baffled because the fuel tank was just filled up which puts the fuel level about 12" or 13" above the fuel pump sediment bowl.
The carburetor throat was completely dry right after shut down but after 15 minutes it was all wet inside and full of fuel vapors.
Can't wait to try the W-1, hope it’s all that its cracked up to be.
Denny Graham
Sandwich, IL

Denny -

The Viton (neopreme) in the fuel valves does the same as in the diaphragms (gets hard after being in deathanol and then allowed to dry).

However, the time-to-failure is longer, due to the function.

The diaphragm has to flex to function, as does the skirt of a "normal" accelerator pump. The neopreme tip of the fuel valve does not have to flex, so hardening does not cause failure of the fuel valves.

Modern fuel valves fail due to the manufacturer eliminating the "staking" task in their manufacturer. I have covered this, and its solution previously.

Jon.

Did a search for "staking" Jon, found two hits thanks. The two threads ran before I joined the forum. Makes complete sense, wider seat and less chance of cutting the Viton. And I gather from your replies that you advocate this for all the rebuilds regardless of manufacturer. Gonna make it a habit from here on in.
tks
Denny Graham
Sandwich, IL

I got fed up with rusty gas that looked like strong tea, so I replaced the entire fuel system on my 53 one ton. When I fired it up, it ran well, but a lot of fuel would run out of the overhauled carb after shutdown. It's a little concerning with the hot exhaust being right there. I pulled the top of the carb off to check the needle and seat. There appeared to be a tiny bit of a metal filing on the seat. I blew it out, and also checked the float height. Seemed ok so I left it as is. Put her back together, and voila, works great! Someone here compared the float operation to a toilet - I think that's a perfect way to describe it!

Making it run and having fun!

Oh my oh my, the patience many of us have developed over the humble Model B and their derivatives. For being one of the of the simplest carburetors ever built it is the most cantankerous dang things to get right. I have worked on them for 52 years and I swear I still have problems. I have all kinds of precision tools and a clean room but the most important item is a strong magnifier and plenty of canned air. Doc.

I've figured out the best use for a Rochester B- - - - -anchoring a trot line when I want a good mess of catfish!
Jerry

I am glad that I ran across this thread. I have been having the same problem with my '51 Chevy 3100. Will start right up when cold, but will not start after having run awhile.
Started it yesterday to back it out of the garage so I could do some work inside. A couple hours later started it up again to drive it the 100 yards to my house driveway to give it a bath.
After the wash started it and took it for a drive of approximately 30 minutes, then parked it. After sitting for about 30 minutes, tried to start it to put it back in the garage, but it would not start no matter what I did with the choke. Lifted the hood and saw that it was dripping gasoline from the fuel line where I have it connected to an inline filter.
This has happened to me several times before. I am new to stove bolts and do not have much experience with them. I did not know that this problem existed with the Rochester carb.
At least now I have an idea of what the problem may be.
Thanks.

A question: I have been using a plastic in-line filter about six inches in front of the carb. Was the glass bowl filter original to the 1951 216 engine? Are there any advantages/disadvantages to this type of filter?