The Stovebolt Site Forums The Shop Area Engine Shop Carb options

Well, my truck stranded me for the first time yesterday, so I guess I need to start looking into what my options are for replacing the carburetor ( I am pretty sure that is my problem anyway). I have a 56 with a 235 and a Rochester carb (all original to my knowledge), though it usually starts easily, I do have problems with it stalling when I am sitting at a light and it is hot. After about a minute or so, I can hear the engine start to slow and if I don’t catch it quick enough with the throttle, it will die. With the throttle pulled a little bit, I can keep it running. The issue yesterday was that I had stopped for only about ten minutes, and when I tried to start up, I could not get it to run. I figured it just needed to sit for a few minutes (so I made my father’s day call) and gave it about 20 minutes to cool, then it fired right up. I raised the idle with the throttle knob and had no problems the rest of the day.
So, assuming my problem is the carb, what are my options for installing say a Carter? I have read several articles in here about how much better they are over the Rochester’s, but would a Carter fix my problem above? Are they still available and how will they retrofit onto my engine? I have overhauled my present carb twice in three years now, and other than some leaking at the cover, and the issues with stalling, I really can’t complain too much. I can live with most of it, just don’t want to get stranded again ( or have it happen to my wife!).

Thanks,

Lee.

"The ABC's of carburetion- - - - -Always Buy Carter!" That was Carter's slogan for many years, during the time they were selling a million replacement carbs for Rochester B's. Now, before you go to the extreme of swapping carbs, take the top off the Rochester and check the float. They're notorious for springing leaks and getting the hollow brass float about half full of gasoline. That allows fuel pump pressure to push the needle valve off its seat and cause a flooding condition at hot idle. Quite often, a simple float change will solve the problem, even without a complete carb rebuild. Be sure to set the float level and drop correctly before reassembling the carb. The chances that a replacement float will have the right settings are somewhere between slim and none.
Jerry

Thanks Jerry, I will check the float and see if it is leaking. I know it was fine when I last overhauled it, and did check the level, but I might have got it wrong and will check it again.

Lee.

Another question: I have the numbers of 1 9/32 for the float level, and 1 3/4 for the float drop; I guess they are correct, but I do not recall where I found these numbers. Can anyone recommend an accurate source for these dimensions? Also, where do you measure from? I have been using the cap surface or should I say the surface of the gasket on the cap since that has always been installed already when I make my final measurements.

Thanks, Lee.

And the float is good, I put it in a pot of hot water and no bubbles. So I readjusted both the float level and drop to try to lower the level of fuel in the bowl. Will report next flight.

And the carb is a B model, though the tag is missing, if it is original, the number is 7004468.

Before doing anything at all:

HARD STARTING, HOT


Difficult starting of a hot vehicle from 5 minutes to an hour after the engine has been operated, can be caused by the volatility of modern fuel. If you have this problem; try using the following method to start the engine: DON’T touch the footfeed (VERY important). Crank the engine over from three to 5 seconds (different vehicles will respond to different times); and then GENTLY (so as not to activate the accelerator pump) press the footfeed approximately 1/3 of its travel. The engine should start, and may run rough. Run the engine at a high idle for about 10 seconds. This issue is caused by volatility of modern fuel. Once the engine has been shut off, the gasoline is heated by the latent heat of the engine, and percolates the fuel from the bowl into the throttle area, forming a mixture that is too rich to fire. If you push the footfeed to the floor (as has been the traditional method of “unloading” a flooded engine) the gasoline continues to flow into the engine (again due to the volatility). By not touching the footfeed, you do not open the throttle plates, and the engine will pump the overrich mixture out of the tailpipe. Once the overrich mixture has been alleviated, gently opening the throttle will allow the engine to start.

The above is from the "Troubleshooting" section of my website.

While I tend not to disagree with Jerry generally, I do not think the float is at fault since you stated the engine started right up after 20 minutes.

You might consider setting the idle RPM maybe 50 RPM higher, which might help with the stalling issue.

EDIT: and if like so many enthusiasts you might be using 93 octane (or av gas or race gas) DON'T! Use the lowest grade fuel you can find at a name-brand station! The higher octane fuel will increase the problem.

Jon

If the float isn't the problem, it may be that your power piston has become stuck or due to lost vacuum from warpage just isn't working right or it may not be working at all. This will allow too much gas to go up into the mast and that will let it run too rich (which naturally will foul up your idle). If you decide to switch to a Carter, you'll need a 2100s Carter (manual choke) or a 2101s Carter (automatic choke). It sounds like you're using manual choke now. I have a 2100s, but it is promised to another member here. I have a fellow looking to see if he has any in a warehouse he owns, but I haven't heard from him in a while. Alternatively you could use the 3211s (auto choke which was designed for 235 from 1957 until the end of production of the 235), but those are really hard to find and consequently more expensive. There were no manual choke 3211s models made. You may see some on eBay but those are mongrels cobbled together from incompatible parts. Any of the models mentioned above will install easily and without much alteration. You'll need the choke heat pickup tube extended, but that's about it. You should find the Carters more well-mannered and pleasant to drive. Good luck!

Those levels are right, Lee. Did you check to see if the power piston was freely moving when you had it apart?

Went back and read, and then re-read your first post. I really don't think there is much, if anything, wrong with your carburetor (other than it is a Rochester )

I think the problem is with the gasoline.

QUOTE "The issue yesterday was that I had stopped for only about ten minutes, and when I tried to start up, I could not get it to run. I figured it just needed to sit for a few minutes (so I made my father’s day call) and gave it about 20 minutes to cool, then it fired right up. I raised the idle with the throttle knob and had no problems the rest of the day." END QUOTE

If the float were bad, or the power valve was malfunctioning, you would have continued to have problems.

Modern fuel, with or without ethanol, causes havoc with driving carburetored vehicles. And vehicles in the mid-1950's were beginning to have hot soak issues. Carter came out with a "hot idle compensator", but Rochester did not wish to pay Carter royalties, so didn't use it. Instead, Rochester came up with a number of fixes, including the infamous slotted throttle body gaskets, and a really useful aftermarket item - the Carb-Airator. Rochester finally relented, and used the HIC on two and four-barrel carbs. (opinion) Rochester's two and four-barrel carbs are among the finest ever made!

The hot idle compensator is simply a heat sensitive valve (bi-metallic strip attached to a valve) that opens and creates a metered "vacuum leak" under extremely hot idle conditions. Used to be automatic transmissioned vehicles had the most problems, but today's fuel means everyone has problems.

Here is a link that shows a number of hot idle compensators, including the slotted throttle body gasket, and the Carb-Airator

Hot idle compensators

If you can locate one of these little gismos, it just might solve your problem (other than hot starts, which my previous post should solve).

And when you do get tired of the Rochester, the Carter single barrel is a far superior carburetor (opinion).

Jon.

Thanks to all for your ideas; I did try the old flooded engine start technique (full throttle while cranking) which did not help, and at that point I considered that if it wasn’t flooded before, it is now. I’ll keep in mind your trick Jon in the future, and since I have a throttle knob, it is easy to up the idle when needed to keep it running.

Jon G, I did not check the power piston when I had it open unfortunately, I just checked the levels and the needle valve area for trash.

I did lower the float level to less than what is specified to see what that might accomplish, or not.

Lee.