The Stovebolt Site Forums The Shop Area Engine Shop Rochester carb leaks

I have a B Rochester on a 58 Apache 31 that leaks like crazy. I rebuilt the carb, tested pump pressure at 6lbs. It seems to leak at the gasket ( not seems, pours out) . When rebuilding noticed needle was not sticking but replaced with rebuild. If needle seats why leaking at gasket above float level? And yes level and drop were set with rebuild.

It seems to me that rebuild kits used to include the copper crush washer where the inlet fitting screws into the carb. The last kit I bought didn't have the washer and I really needed to use a new one. Gas has a funny way of sneaking around and the leak at the washer looked like a leak at the gasket. A new washer fixed the problem.

I don't have an answer for you but my original carter starting leaking on my 54 3100 and I rebuilt it. No change. It still leaked like crazy. These carburetors are known to warp. I found it hard to believe after 68 years mine would suddenly warp but I had no other explanation. I purchased a rebuilt one from a carb shop in California and couldn't be happier with it.

Pump pressure shouldn't go as high as 6 psi. 3 to 4 psi +/- 1/2 is the limit. You may be overcoming the inlet needle valve.

If you are running Ethanol, lower the float.

Rochester is known for leaking but Carter not so much.

Taking your carburetor to a professional (one who has the experience, the equipment and a selection of hard to find carburetor parts ) is a smart move IF you first make sure everything from the gas cap to the carburetor is in tip top shape.

If you must run Ethanol in a truck with original fuel system, don't let it sit 6 months unused. You must drain the fuel regardless off what additives you pour in the tank.

If the new copper gasket (as Gord suggested) on the inlet fitting doesn’t fix the leak, there is a known issue with Rochester “B” carburetors, where the top to bottom flange gasket leaks. Replacing the gasket usually doesn’t solve the issue. The flange is known to warp and a fellow ’bolter Jon G, has a post that shows how to straighten. Although not a easy fix, it will fix this issue. Here’s a [LINK].

I mis-spoke about my carb being a Carter. I had Carter on my mind because I am rebuilding one for another project. The one that leaked on my 54 was a Rochester.

I use an electric fuel pump which has 2.5 pounds of pressure. That is truly all you need with a 216, 235 or 261 unless you've modified it to drink lots of gas. There are at least 5 reasons a Rochester B will leak fuel. Unfortunately only a couple of them are easy to fix, but yours sounds like more of an easy situation. I'd take the carburetor apart and check to see if the float is working and working freely (be certain it isn't binding on the float bowl). Blow air (with your mouth) in the fuel inlet and lift the float so that it reaches the point where it will close the fuel valve (some call it the needle and seat). Look at the fuel inlet orifice. The hole in the seat if you prefer. The cheap rebuild kits all have very large orifices...when I was doing the Rochester study, I found 3 different sizes. (see image below) If you have the large one, your float & fuel valve probably can't keep up with it. That is to say if your pump is outputting 6 pounds of pressure and you have that large orifice, it isn't going to be easy for your float to regulate things. The fiber washer for the fuel valve is generally as good or better than the brass one in my experience...particularly with an older carburetor. It should have been in your rebuild kit. If fuel is pouring out of your gasket (between the float bowl and air horn), something isn't working with your float and fuel valve. Please let us know what you find.

Thanks everyone, ironically the leaking got much worse after I replaced the pump last fall. I’ll try to reduce the pressure and see what happens

I have been battling the same problem with the Rochester on a 216 for quite a while. Rebuilding the carburetor seemed to help for a little while, but the problem has resurfaced. On another site an individual was having similar problems with a 2bbl and it was suggested that the aftermarket fuel pump could be over pressurizing the system and pushing fuel past the valve. The remedy mentioned is to adjust the float a little lower on the upper end of its travel thereby causing the fuel to overcome more resistance. I have not tried this yet, nor has the other person. It sounds like sound advice to me and in theory it should work. I’m tired of fighting this $&17 carburetor! It’s to the point that I look for excuses to not drive. It’s not much fun to have fuel pouring all over the manifolds! Any gurus care to give the 2 cents worth? Besides Carter, budget doesn’t allow at the present. PS float has been replaced also.

I understand that you think your budget won't allow the purchase of a Carter YF, however, if you aren't driving the truck, what's the point in having it?

The cost of a new Carter is little more than two or three tanks of gasoline. So take the money you've been saving on fuel by not driving the truck and put it toward a Carter.

TODAY, the most common reasons for a large fuel leak on ANY carburetor:

(1) Excessive fuel pressure
(2) Incorrect fuel valve orifice (cheap FLAPS rebuilding kit)
(3) Excessive fuel pressure
(4) Defective float
(5) Excessive fuel pressure
(6) Improper fuel valve adjustment
(7) Excessive fuel pressure
(8) Fuel valve seat not seated (galled threads)

Oh, and did I mention excessive fuel pressure?

Thankfully, there are gismos called fuel pressure gauges, so an enthusiast does not need to guess.

And in for what its worth category, I have personally tested some new fuel pumps packaged in a well-known USA company box, made elsewhere), that tested with a fuel pressure NORTH of 10 psi. Just because it is new does NOT make it better.

TEST!

Jon

I second that.

Get a Malpassi Filter King pressure regulator/filter and be done with it: https://www.fuelpumpsonline.co.uk/m...-glass-bowl-86-mm-unions-fpr004-34-p.asp

Or you can use the same fuel pump I use. This is it: https://www.amazon.com/gp/product/B00496RE82/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1

I've had 2 of these. The first one lasted over 20 years and didn't actually stop working. I just replaced it thinking it had been in use long enough and put the used one in a little box under the seat. It outputs 2.5 to around 3 pounds of pressure...and as I mentioned that is all you need. Since I wasn't using the mechanical fuel pump (and had no reason to given the state of mechanical pumps today), I ran oil filter lines out that hole through a block-off plate I made to allow me to use a spin-on filter. Images attached.

Stovebold6,

Where did you install the regulator/filter (pictures)?

Thanks

Sorry, don't have a picture of it, but it's mounted on the firewall (driver side) a bit higher than the carb (close to the hood hinge), cause I wanted it as much away from the engine heat as possible.
And yes, I have re-routed my fuel line over to this side for the same reason: preventing vapor lock with modern fuels (E-10 over here in Germany).

Nest time I get to my shop, I snap a picture for you.

Otto, you answered my next question and that is if anybody had success with a Carter yf conversion. Some people say it will bolt right up or is there alot of adapting?

My truck came with the Carter on it so I didn't have to do anything, However, it has the stock linkage and attaching points for the spring , etc so I think it goes right on.

It will bolt to the manifold without an adapter. It does have a spacer which I presume the Rochester uses as well.

I think the only things you might need to look at closely are the throttle and choke cable mount. Even that might not be an issue since Carter designed the YF to be a direct bolt on replacement for the factory carburetor.

A couple of the pics are made before the final fitting of the cables. You can see the Sharpie marks on the throttle cable. Anyway, this shows you what the bracket looks like for the choke and throttle attachment.

It bolts up with very little adapting at all. The 3211s was made for your 1958 engine.

Don't think that buying a core Carter and rebuilding it with a FLAPS kit will solve everything; look at item number 2 in my post above.

But if you buy the SPECIFIC one Carter recommended, it bolts on and hooks up with a minimum of issues.

Jon

Stoveold6,

Thanks for the reply and info. Will watch for a picture in the future.

Thanks again!

Harbor Freight has a basic pressure gauge for $16.

... and it reads vacuum too!

A comment on the copper washers used in early production for the fuel valve seat:

Copper corrodes badly!

Rochester superseded the copper with fiber washers, and later superseded the fiber washers for the fuel valve seat with an aluminum washer with some type of coating.

The problem arises in that the copper, the fiber, and especially the coated aluminum are of different thicknesses, so the rebuilder needs to be aware of the original float settings.

NEVER trust the data that comes in a FLAPS rebuilding kit. Some of it is probably correct, but I have seen so many errors that I would never trust this "data". CORRECT data is contained in the Chevrolet factory service manuals.

Jon

I have adjusted the float and so far there is no fuel pouring over the manifolds. Let’s keep our fingers crossed and hope this remedies the situation.

Correct fuel pressure from the pump, lower float setting, correct inlet needle valve, all these help remedy fuel pouring out or flooding the engine. The other issue is weeping or small gradual leaking that's caused by warping. Internal leaks can also happen due to warping. Lowering the float would be the ticket if fuel was always level (didn't move around) with the bowl and horn junction. Braking, acceleration, curves and parking on hill side means the gas inside can find a gap. If you own a Rochester B, you might as well accept a little leaking as long as the engine runs decent.

Ok guys, bought pressure regulator, set as low as possible, set engine at about 1500 rpm, 1.5 lbs read and SLOWLY seeped at gasket.
Good enough for me. Turned engine off and starts to RAPIDLY pour from gasket. Screws are tight . What’s up?

I think you might have two issues going on.

The leak is likely due to warpage of the mating surface of the carburetor base.

Pouring out after shutoff points to the bowl being overfilled due to an incorrectly adjusted float or faulty needle and seat. Gas is spilling out of the bowl into the carb throat and then leaking out the base.

Even if you fix the leak at the base, the gas is still going to pour into the throat and pool on the intake manifold causing a flood condition the next time you start it.

Rochester is "what's up". They make pretty good paperweights- - - -stinky ones, if they've had any gasoline in them recently, though!
Jerry

Try this link: https://www.thecarburetorshop.com/Troubleshooting.htm#Fuelleak

Jon

Problem solved ( for now). Took top off to readjust the float and noticed a piece of plastic between the needle and seat. No idea how and don’t care because this truck never ran better. Thanks everyone for the help

That's excellent. I love it when it's an easy fix and nothing was actually broken to begin with.

[quote=Jon G]Or you can use the same fuel pump I use. This https://www.amazon.com/gp/product/B00496RE82/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1

Decided to try to order this. Amazon won’t ship this item to me in California. Guess I’ll have to get it shipped to my brother in law in Nevada & have him ship it to me.

There is merit for having a fuel filter just before the carburetor.

It looks like all the new mechanical fuel pumps made for our engines now come from China, Russia and Romania.
Time will tell how reliable they are. My gut feeling is that the change to electric pumps is a given.

Charles, consider a safety circuit to disable your electric fuel pump in case of an accident.
Many add an oil pressure switch (connect contacts in series) to interrupt the voltage to the fuel pump.
Optionally, add a under dash spring loaded toggle switch or pushbutton, to prime the carburetor fuel bowl, if the truck has been sitting along time.

Most fuel pumps this old are rebuildable.

IF THE CASTING IS DECENT: made in USA quality fuel pump repair kits are available from "Then and Now Automobile"; there is no need to purchase a brand new off-shore-made pump.

And even though I have high performance, high pressure electric pumps on both my old vehicles (both have carburetors that I set up for the pressure), I still don't generally like electric pumps. But one of my vehicles has two 625 CFM, and the other a single 850 CFM; and requires the volume.

Jon.

I just sent my glass bowl pump for the '50 to Then and Now for a rebuild.

The kit is $52 to do it yourself and their rebuild service is $115. $63 seemed like a bargain to me for them to do the work. He'll machine the surfaces if necessary and straighten the body if the bowl doesn't seal.

I love the look of the glass bowl pump. I attempted to rebuild but got too much play in the "arm" or whatever it's called going into the block to pump the gas. I'm settling for a "plain jane" pump for now.