Carburetor flooding

[bochyhawg]

I took the carburetor off my dual plane manifold yesterday and noticed raw fuel in the inner two holes. I had decided to put a taller air filter under the hood since I had the room and it was cheaper. Could this affect performance? I used to have a one inch spacer under the carburetor until I had trouble with the gaskets leaking. There is a lot of grime on the outside of the 390 Holley and it needs a rubber plug replaced. It could be leaking a little around an adjuster screw on the primary bowl. Im kind of hesitant to take it apart myself even though they tell me rebuilding holleys is easy. When I flip the carburetor upside down I can’t blow air through it so the float seems to working properly. I may invest in a one of of those washable air filters and see if that helps the flooding condition. The original one barrels on the 300 six gave me a lot of trouble too. It could have been the oil bath.

[Nitekruizer]

IMO, the size of the air filter won't make any difference to whether or not your carb is flooding. You could have an internal leak of some sort. If this happens after you've been running the engine, it could be a "heat soak" issue, especially since you removed the spacer. Have you checked the float level? Could it be pushing fuel up the vents? If you can, leave the filter off and look at the carb after the engine's been shut off and see if you can see the source of the leak.If you haven't rebuilt your carb, you may want to. There not terribly difficult and the kits come with diagrams and instructions. I've rebuilt Holleys, Carters, Autolites and even a Rochester. I honestly couldn't tell you which one was easier.

They all went back together without too much trouble. It's a learning experience, like everything else with these old trucks.

[bochyhawg]

Thanks for your opinion nitekruiser. It would seem logical to me that the 4” air cleaner allow for air flow than say a 2 1/4” tall air cleaner. I’ve not checked the float level yet. I imagine I could do that with the carb off the motor. And check for leaks like you said. I bought some more rubber caps today. It could have been sucking air through that port. Any tips for preventing the gaskets from leaking above and below the spacer?

[bochyhawg]

I’d really like to tear into that Holley but I don’t have the time to waste. A secondary reason I don’t want to buy a new carb, other than the high price, is because in ten years I could be having the same carburetor condition. They tell me ethanol is bad for carburetors. Didn’t they build 300 inline sixes all the way up to nineties? I’ve heard guys say the engines get 17 mpg. Fuel injection couldn’t be any more difficult than rebuilding a carb. I already have a high amp alternator under the hood. I still plan on checking the floats after I find a suitable screwdriver and maybe cleaning the outside of the carburetor with some raw fuel and a wire brush. Holley carburetors seem to have some good metal in them.

[markguiver]

Check the float. It could be that the solder on the float itself has degraded and the float is full of gas. Turning the carb upside down and blowing air through it would not diagnose that. Like anything mechanical, carbs or fuel injection require maintenance to keep them in an optimal condition. You should be able to pull the carb, take it apart, clean it, and reassemble it with a rebuild kit in one day. It's not hard if you have a good clean work surface to lay out the parts in an orderly way. IMO a well tuned carb is very close to fuel injection in function, and both work better when properly maintained. I don't consider maintenance a waste of time, it is what it is.

Mark.

[bochyhawg]

I bought a trick kit yesterday. I guess I’ll disassemble it when I get time. Does anyone have an opinion or experience using pinesol and hot water to clean? The appeal of pinesol is that it isn’t very toxic. Twenty years ago i soaked an Autolite 1101 in denatured alcohol. The trick kit recommends lacquer thinner. I’m still not sure why the carburetor began to flood. I had installed a defective brake booster on the truck. A lack of vacuum may have affected the carb. A clean place to disassemble the carb is another project. I guess I should take my time and do it one step at a time.

[bochyhawg]

I worked on disassembling the carb yesterday. My workspace wasn’t as clean as I would have liked but I had all the tools handy except for a large Phillips head screwdriver. I also found most all the parts I needed in the kit. When the top bolts were removed from the primary bowl, a white powder was found on the bolts. I’m pretty sure this means water has found its way into the carb. In fact, this residue was throughout the carb. I checked the float out; it’s a nitrophyl material. It looked degraded. I also noticed the marks from the needle weren’t centered on top of the dome on the float assembly.The reason the carb is flooding might be because the float is absorbing liquid through tiny cracks and not closing the needle completely. There was a 6 or 9 on the old power vavle. The white residue was covering covering half of the surface. Today I’ll try to finish taking it apart. There is a brass part with an o-ring still stuck in the center block of the carb; I’m not sure if it pulls out or twists out. One of the screws holding the throttle plate rod has been damaged and at the end of the day I lost a small snap ring. There was what looked to be a ball bearing in the bottom of one bowl. I took pictures as it come apart for future reference. It was a lot of fun!

[markguiver]

Taking pictures is a good idea for when you start to reassemble it. I've done that before myself before too. One trick I use when taking those little snap rings off On carbs, distributors, etc..., is to use a small magnet next to the snap ring so if it pops off the magnet will catch it. That also helps when replacing them in case they want to fly off when snapping them back on. The white residue is from water oxidizing the aluminum and could be from getting water in the tank or from the ethanol that's in the gas now from absorbing moisture out of the air.
If the rebuild kit didn't come with a new float, Summit as well other places carry replacements. It's a good idea to replace the float(s) anyway just to save headaches later.
Looking forward to hearing how it all worked when you're finished.
Mark.

[sargentrs]

As long as your having, really clean that carb up with your own home made soda blaster https://youtu.be/5Fj-qiZj_WU

[bochyhawg]

I got the carburetor soaking in diluted pinesol. I might scrub a little with a brush this evening, dry with compressed air in the morning. My neighbor gave me one of those blow guns for cleaning with compressed air but he told me it was for liquid cleaner such as kerosene. I like the idea of spraying baking soda on the carb. Most of the brass pieces are soaking in mineral spirits. I even went so far as to disassemble the choke. I ordered new floats and springs. I might put a stiffer spring in the secondary vacuum for fuel economy. There was significant wear on the needle valve assembly. A minor adjustment may have fixed the flooding issue. The old power valve had had the lick. The teat appeared to wore down. The old one was j6 and the new power valve was stamped l7. If I don’t get the carb back on the truck tomorrow, I’ll have a rainy day on Thursday to fool with it.

[bochyhawg]

Well,the carburetor going back together fairly well. I rinsed the cleaner off with hot water and blow dried the parts with compressed air. I made a few mistakes, but we got those corrected. I been trying to figure out what the red cam behind the electric choke is supposed to do. My truck is Manuel transmission; so, it can’t be operating passing gear? I could probably use an extra hand getting the gaskets right on top of the throttle body and vacuum secondary bowl. The number on my accelerator pump nozzle is 25; that’s one reason why I’ve been getting good fuel economy from the carburetor. Because the power valve has a higher number that might save fuel also. I put some better springs in the carb. After the old nitrophyl floats dried out, I could hardly tell them from the new ones. The new float springs were a little longer and stronger. I wish I’d took more time with photos, especially how the parts move. The first mistake I made was fiddling the the accelerator pump actuator (that is moved by an orange cam) when trying to remove the carburetor from the truck. Without the one inch spacer under the carburetor,I had to grab a socket with pliers to remove a nut. I might work on it a little more in the morning. I had to hunt wire pliers to drop the check valve under the accelerator nozzle this morning.

[bochyhawg]

We started the truck today. It started first turn; but it wouldn’t idle down. Those throttle plates and rod that I removed during cleaning gave me the most trouble during the rebuild. I thought I might have to order new screws for the throttle plates; but I finally got it together and it seemed to be closing properly. New screws may help to center the throttle plates. During visual inspection the rod and plates didn’t seem to be bent. A new throttle rod isn’t overly expensive. I’ll at least need to change the screws on the throttle plates. I know they are supposed to be slightly open during idle; but I’m guessing it’s idling near 2500 rpm. Another concern is that we didn’t see any fuel squirting out the boosters when the throttle was opened. I’ll have to take the carburetor off the truck again.

[CH3NO2]

Throttle plates have a beveled edge. If you put them in upside down they will not close properly even though they look like they are closed they won't seal.

[bochyhawg]

I’ll check that out. I noticed that there were numbers on the plates but hadn’t considered the edges were beveled. It pays to have pictures. I created a nick on the bottom of the throttle body when I had the throttle plates fastened down wrong. The trick was to fasten while the plates appeared closed.

[bochyhawg]

I took the carb off yesterday, fixed it and put it back on today. I was going to do some measuring with the micrometer but i got the throttle plates closing all the way first. They weren’t upside down,but I reckon I turned them 180 degrees. I fiddled with spring and the throttle arm rotated against the fast idle screw like it supposed to. It didn’t start the first time today but after turning the fast idle screw it fired right up. It may need some more adjustments it’s not accelerating smoothly. I may connect a tachometer and run it some more in the morning.