I'm having an intermittent stumble/stall problem during acceleration, along with idle problems. Usually the car idles fine, and will accelerate fine, but sometimes if I've been idling a while, such as in stop and go traffic, it will develop a bad stumble during acceleration, and the idle speed will start to wander, and it will start to miss. I had a problem with the carb boiling over and leaking fuel from the bowl, but I seem to have that fixed now (phenolic spacer, lowered the float level, and cleaned up the gasket surfaces). I can't ever reproduce the problem in the garage, but today its was doing it when i got to work, so I pulled of the air cleaner and took a look while it was running. The carbs not boiling over (and was barely warm to the touch), but one of the nozzle bars is dripping fuel. Probably one big drop every 5 seconds or so. I assume this is the problem, but why is it happening? Its coming from the center of the nozzle, so I wouldn't think its one of the gaskets at either end leaking. Only the passenger side is dripping so I wouldn't think its a fuel pressure problem. Maybe it just needs cleaned out? Full engine details: Stock 8BA flathead, single carb on stock manifold Rebuilt 49-51 style carb with about 350 miles on it. Stock mechanical fuel pump Mechanical advance distributor (chevy) set right on the timing mark.
Needle and seat are fine. Fuel pressure is a good question, but its just the stock pump not an electric.
Have you rebuilt the carb ? Keep this in mind that the fuel we are forced to use now with ethanol is not good for the rubber inside the carb . The fuel has sugar in it and when it breaks down from heat it does nasty things to any rubber parts you have in the carb like the seats . If you rebuild the carb make sure you buy a modern kit and not an old kit that has been around for a while . Also check your power valve and make sure that not leaking too . Just a thought . Retro Jim
I had to run a fuel pressure regulator to drop the fuel pressure on my FE running a stock pump. It helped. Not sure if that is your problem, but it could be. The 94's don't like much fuel pressure.
The newer style P valves don't fit very well either, I had to do a little careful grinding in my carb bodies to make them work on my old 48. I went to a 4.5 PV, but I had dual 94's on a 59AB flattie. My 94's would do funny things if they were getting any more than 4 PSI...
Hello......I had a problem on my 1936 ford also.......tried everything just like you are doing.....what work for me was a new fuel pump.....ever since I don't have a problem..........good luck....Big Bad John
I had to use 2 very old stock float valve assys in my 94's even with a stock pump. The new type rubber disc type valves were useless. My Engine startup thread: http://www.jalopyjournal.com/forum/showthread.php?t=511015 The float valves are mentioned in a subsequent reply (#18) Mart.
The carb is rebuilt, and has very low miles (~350 over 2 months), so hopefully the seals aren't degrading already. The needle is the proper kind, not the crappy disks. I've tested it, it seals really well. Fuel pressure or leaking power valve sound possible. I can swap the spring in the fuel pump with a known, good 4 psi spring. How could I tell if the power valve is leaking?
Well, according to the Holley website, if you can screw the idle mixture screws all the way in and it still runs, the power valve is leaking. Mart.
And almost any PV purchased in the last several years will have wrong configuration at gasket seat, making a leak very possible. Pressure..."stock" pump means nothing, many are manufactured now with diaphragm springs way to stiff with up to 7 pounds pressure. Measure. Nozzle bars...'49-51 has the V shaped onew with high point at middle. Pullem, look at the air bleeds...there are two, idle and main, near front of each, TINY hole at bottom of a larger hole, must be clean. Also clean brass part in middle thoroughly.
Thanks for the input everyone. The seemingly random nature of this problem has been frustrating. Plan of attack: 1. Check fuel pressure 2. Clean nozzle bars. I read somewhere else that clogged idle passage could also cause these symptoms, so I'll clean those out too. 3. Check power valve. I may try replacing it with one from the old carbs in my stash. I can't wait to limp this thing home in Friday afternoon rush hour traffic!
You probably clearanced within the bowl to fit the big knob on the spring. The other are is where the thing seats on gasket beneath the bowl...correct one has flat ring matching where gasket goes, late one is tapered there and has gasket ring outboard of where it is needed.
This is just a hunch based on my recent findings, but if it's too old the rubber might be too stiff. If using an older one make sure it moves freely against the spring. The vacuum has to suck it shut against the spring pressure. Mart.
I have had some bad Rubber fuel lines from the stock pump to the carb also. The new gas is eating the original hoses. I've seen them swell up and almost close off. Check it..
Put a fuel regulator inline with the carb,you only needs 2.5 to 3 psi of fuel. If you have more than that, you will have the problems you are having now.Also make sure the float level is correct.Trust me l run them all the time l got 6 carbs on one of my cars now and 4 on another talk about tuning and make that run right.
This subject has been talked about 100s of times on the Hamb. l could get into it but this will be the best for you. Here is a link with lots of great stuff for you to look up on 94s and a few things that Bruce has talked about to.You could do a search on here but this is a link with a bunch of other link on here all compiled that will tell you tons of info.So read and fill your boots my friend... http://www.jalopyjournal.com/forum/group.php?do=discuss&group=&discussionid=289
Vintage Speed in Florida has modified power valves & excelerater pumps that I use with great results in my 94's
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