JohnnyBs68S

I just finished rebuilding my carb (to adapt a TV cable to my '68 350-2bbl), and when I first put the key to it, it was spewing fuel out the idle vent on top of the carb. Replaced the float which fixed the fuel spewing out the top, but now its just dumping gas down the throttle plates. The engine wants to fire, but after I stop cranking and get back under the hood I can hear fuel dripping, I can see down the throat of the carb and see it dripping from the venturi onto the throttle plates, for several seconds after I stop cranking! I don't think that is normal.

Re-reading over the directions, I may have used the wrong washer in the center screw holding the venturi assy into the main body. Could this be the source of my excessive fuel leak?

Thanks for the help.

Tadpole11

Did you adjust the float with the gasket on or off the bowl? If the float was set with the bowl gasket installed, that would throw off the float rise/drop. That was my experience years ago with a Rochester 2GC. That's the only problem I ever had with the carb and it was my fault. Good luck....Tadpole11

JohnnyBs68S

Thanks. I thought about that too. Both the instructions w/ the kit and a NAS Mitchel Manual I have state to measure both float level and drop w/ the gasket installed. The MM also states pretty clearly that a special washer needs to be used on the center venturi cluster screw otherwise it'll leak fuel. That describes my problem exactly. Wished I noticed that before I put the carb back together (DOH!). Need to see if I can get that screw out w/o taking the top of the carb off (again). Keeping fingers crossed............

JohnnyBs68S

I was able to get the center venturi cluster screw out w/o removing the carb top. I found a hard fiber washer that looked like it'd make a good liquid seal, tweeked it to fit good enough, put it back together, and its still flooding. Although it doesn't appear that the fuel that is dripping onto the throttle plates is coming from this screw head.

Last resort on this carb is going to be another rebuild. More waiting on parts. If this doesn't work, or if I find that something is cracked, looks like I'll be looking at a new 4-bbl / Perf RPM / cam / lifters / springs. And I MAW...........

Tadpole11

It sounds like there may be an "O" ring missing somewhere?? Just a guess, good luck.....Tadpole11

Sugar Bear

The problem is likely in the float height adjustment or the needle and seat. Are you certain that the old washer was removed from below the seat and not left on the carb fuel bowl? Did you replace the washer under the seat with a new washer and make it quite tight?

Doubt the problem is with the possible wrong washer at the venturi cluster.

Good luck!

Oldsmaniac

Fired the 400 yesterday for the first time in the turnpike cruiser. It has the 2bbl which I rebuit. Fuel was spewing out of the top vent. Opened it up today and adjusted the float now all is well.

JohnnyBs68S

Thanks. I've verified the float level multiple times now, also removed the needle seat and made sure the washer under it was the right one, and that the needle wasn't damaged. Like I said, once I put a new float in, the spewing out the top vent stopped, so I don't think I have a float level or leaking needle valve issue any longer. The only ambiguity w/ setting the float level is: which side of the "seam" on the float do you use for the measurements? In order to "err on the safe side", I've been using the top edge of the seam, which would result in a lower float level than if I had been using the bottom edge of the seam. Something else internal isn't sealing right. I've got a new rebuild kit on order and will go through it w/ painstaking detail this next time. I've got a Rochester service manual now for reference when putting it back together. If I find out what I did incorrectly during the previous rebuild that is causing this issue, I'll report back.

Sugar Bear

Been thinking about this...the power valve in the base of the fuel bowl may be leaking. Do you have the old one to try?

JohnnyBs68S

A new power valve is not included in the rebuild kits, so the old one is the only one I have. I'll pay extra close attention to this, as well as the plunger that activates it. It always seems like this plunger is a bit sticky and seems to bind a little when working it w/ my finger. Some of the instructions says this plunger is removable, but it appears to have been swedged / crimped into the upper body and doesn't appear to be removable. But yeah, if the power valve is leaking (for whatever reason), it seems like this could result in unnecessary fuel being allowed to flow down the carb throat. Thanks for the idea.

I pulled the carb back off the engine yesterday afternoon. When the rebuild kit arrives later this week (c'mON RockAuto!!), I'll begin the teardown.

Sugar Bear

The plungers are staked in place. Repeatedly pushing the plunger in and letting it snap back will often get it to release; however, I would try to clean it and free it up by getting carb cleaner in it and trying that first. If it has to be removed be careful to catch the spring under it, and then it could be thoroughly cleaned, polished and staked back in place. The valve really has to be able to move freely without any sticking or binding.
Good luck.

JohnnyBs68S

Thanks Sugar Bear. I was able to get the power valve plunger out and cleaned up and smooth again. It also seems that I used the wrong gaskets under (not only the center venturi screw, but also) the power valve and needle valve, both of which were probably contributing to the flooding. While its been at least 10 years since I rebuilt a carb, I've never made mistakes like this before. I really Homer'd this one, DOH!

Good news is, its running under its own power again. Need to tweak the TV cable and check fluid levels again, but that's another thread.........

Thanks for the help, all.