The Stovebolt Site Forums The Shop Area Engine Shop Setting carburetor float on an original Rochester 1 barrel

I have a Rochester 1 barrel carburetor on my 235 in a 1947 pickup. The carburetor has been professionally rebuilt but the engine is running way too rich and I can't get it adjusted properly using the external setting screws. I want to try resetting the carburetor float and I was wondering if anyone on this forum can assist me...or if anyone knows of a youtube video that shows how this is done. Thanks,

Here's a description of the float circuit:
Setting float level

A professional re-builder should have set the level and drop for you.

My guess is the power circuit is not working. Maybe a stuck piston or no vacuum. Vacuum port on the base of the carb must not be blocked by a gasket.
Power circuit

The problem is probably not a float level issue. The "power valve" is controlled by a spring loaded vacuum piston that is held up by manifold vacuum, through a series of drilled passages in the cast iron throttle body and the aluminum main carburetor casting, then through the top casting. A vacuum leak at either of the two gaskets will allow the piston to drop, and hold the ball bearing valve open, bypassing the main jet. A Rottenchester B carburetor is about the worst excuse for a carburetor that's ever been invented- - - -all because the GM bean counters got too cheap in the early 1950s to keep buying Carter carburetors and decided to start making their own carbs in-house.

A blocked vacuum passage can be caused by using the wrong carburetor to intake manifold gasket, incorrect or damaged gaskets in the carburetor, or a vacuum leak due to warping of the top casting caused by overtightening the 4 screws that hold it to the carburetor body. There's a tech tip somewhere on the forum that covers straightening a top casting, using shim stock, a steel plate, feeler gauge blades, and a toaster oven. Polishing the brass power piston with a felt buffing wheel and jeweler's rouge is also a good idea. After you cover all the above bases, try lowering the float level about 1/32" at a time below the factory setting.
Jerry

Another vote for a defective power valve.

The Rochester to a 1947 is aftermarket.

The correct original and (opinion) far superior carburetor would be a Carter W-1 tag number 574s.

While it is very easy to throw rocks (deservedly) at the Rochester; a rich running issue may also be created by a defective fuel delivery system. That carburetor shouldn't see more than maybe 3 psi. Virtually no electric fuel pump may be used without some method of reducing the pressure. Also, there are some new fuel pumps that produce way to much pressure.

Check your fuel pressure with a pressure gauge before going into the carburetor. If the carburetor were truly "professionally rebuilt", then it should last a few thousand miles without issues.

Jerry must be in a good mood today; normally he would tell you the primary use of the Rochester B is an anchor for a catfish trot line ! I cannot really agree with him as that would be water pollution. A better use is a doorstop !

Jon

Where could I purchase a new Carter W-1 tag number 574 and would I just remove the Rochester and bolt it in place. I ready to try something different. ray

My first Pontiac Tempest came with a Rochester model BC, meaning it had the thermostatic choke option. Other than always having a slight flat spot off idle no matter what we did, it worked fine and delivered decades of craptacular, flat spot off idle service. Car got 27mpg on the highway, can't ask much more than that from GM's first postwar four in a car that was bigger than a Beetle.

Finding a new old stock Carter W-1 is about as likely as running across a chicken with lips- - - - -it's been many decades since the last one came off the assembly line. You could search Ebay, etc. for a good condition used one and get it professionally rebuilt. RUN- - - - -do not walk away from the offshore-made copies of any carburetor- - - - -their quality control is almost nonexistent, and they don't always duplicate the original design accurately. One other option would be a Carter YF single barrel carb for an American Motors/Jeep 232 cubic inch six. Other than a bit different throttle linkage geometry which might involve some creative tinkering, it will be compatible displacement-wise with the 235 stovebolt engine.

www.ebay.com/itm/147315403980?

Jerry

Buck, I wrote the article about straightening the Rochester castings using a gas BBQ grill. It was supposed to become a tech tip, however I am not sure it ever did. I'll search and see if I can find it. If the carburetor was rebuilt and the power circuit wasn't addressed it was definitely not rebuilt professionally.

Sadly you cannot buy a new Carter YF carburetor unless you get really lucky and find one on eBay or Etsy that was never used and has been sitting in somebody's shop for a long time. Fortunately Carter YF carburetors respond well to a good rebuilding. I can't really say much positive about Rochester B type carburetors.

You can use an electric fuel pump but only if you get the right one. Since 1997 I've used an AutoBest F4027. It produces 3 to 3.5 psi and works very well. Cost is about $30 on Amazon.

HERE is Jon's Tech Tip on straightening the castings on a Rochester Carb. Open the link and then download the 2nd PDF file. It takes a bit of setup to straightening a carb that might not be within everyone's capabilities.

I think your best approach would be to find a Carter YF carb and rebuild that.

Should probably note that per previous posts by "bucktruck", his 235 is a 1959 vintage, so a Carter W-1 isn't what originally came on his engine.

With this info, perhaps Jon "carbking" would chime in with some more pointed suggestions on which YF might be best for him to pursue.

"bucktruck" - Speaking of seeking a suitable carb, once you decide what you want specifically, post an ad in the Truck Parts Wanted forum and folks will gladly try and help you find what you seek.

Dan - looks like I need to take a course in remedial reading !!! I saw 1947, and completely missed 235.

The YF with manual choke for a 1959 235 would be 2100s, with an automatic choke 3211s.

Jon