I am working with a 355 in a 68 camaro. It has an automatic. It is running a 650dp mech. secondaries, I rebuilt the carb and put it on the car, it ran good but the floats on the primaries kept on rising, I would adjust them correctly but after running the car for a sec. the float level would start to rise until it bubbled over. So I took of the primary float bowl and cleaned everything throughly. It worked great, but now only sporadically it won't idle, it just dies. It isn't flooding because it starts right back up, the float level is good. It will start running fine again, and then out of nowhere it won't idle, i checked for vacuum leaks, checked the idle mixture and all seemed fine.

How did it run before you rebuilt the carb?
Did you only remove the carb, or other things as well, like the intake manifold?

Had a different carb on before, that was too bad, we did take off the intake, but i would say I did a pretty good job of putting it back on, so i don't believe there are any vacuum leaks around it. also I am thinking maybe some dirt is getting stuck in the carb?

I would think dirt is in the carb also. You said the float boals kept coming out of adjustment. I don't know, but maybe dirt was keeping the needle from seating properly? If you cleaned it up, and that is no longer a problem, I would think it might be possible dirt has gotten into and clogged up a passage way. Whenever I do a rebuilt, I blow out all of the passages with compressed air. Maybe disassemble, blow it out, and try again. Do you have a fuel filter? How old? Maybe also a good time to replace that. The intermittent problems are the hardest for me to diagnose, but from what you said about the float problem and dirt, I would start with the above.

I went through the same thing with mine after sitting around for years. Check the power valve and the gasket it can get cocked in there and allow fuel to run into the manafold causing a rich condition. Also make sure the main body of the carb is flat they will warp over time and allow a vacuum leak to another area. Just some things I went through.

Yeah, I will go through and clean again, fuel filter is new, no vacuum leaks around base, sprayed carb cleaner all around carb with no affect. The powervalve and gasket are fine, it is not a rich condition, it just flat out won't idle, it completely dies.

[This message has been edited by cody (edited 03-17-2002).]

Will it eventually idle when you adjust the idle-speed screw to an extreme? Before panicking and going to dismantle it all again, perhaps make double sure that the speed screw on the primaries is working and set. I am sure you have already done this, but you never said, so I figured I would put the bug in your ear just in case. http://www.camaros.net/forum/wink.gif This won't solve any problems you may be having with the floats, mind you. That would be perhaps due to dirt in the needle/seat, or another possibility is that your fuel pump is delivering too much pressure, thus forcing the float needle off its seat.

The floats are fine know, i figured the same thing about the pressure so i turned it down from 7 to 6 psi, the idle screws are adjusted right but i havn't tried messing with them while the car is running. but i assume they work because the car does idle sometimes.

Indeed, you will need to tweak the speed screws with the engine running. With the automatic, you will want to set the idle so it is around 750 or 800 RPM when in drive. Naturally, you can't get out of the car with it in drive, so have a friend stand on the brake and read the tach to you while you adjust the screw. I think a ballpark figure is about 1000 RPM in park, so try that if you have nobody to help you out with the setup.

Sounds like maybe a vacuum leak to me. You've probably already checked the obvious, but I've heard stories about bad brake power boosters/check valves and bad vacuum modulators. You can double check them by disconnecting and plugging the lines.

You might want to double/triple check that fuel pressure too - I've seen regulators that allow pressure to creep up at idle speeds.

Oh, one more thing - I've seen idle screws that would slowly loosen and let the idle drop. You can fix that by carefully nicking up the threads with a pair of pliers.

[This message has been edited by Eric68 (edited 03-18-2002).]

look down the top of the carb to the left and right of squirter there are some holes 2 on each side about the size of a paper clip
blow thwm out and run a piece of wire through them see if that helps

also make sure you have the metering plate gasket for a 650 dp ask for hte one that is for what is it a 4777 I am pretty sure that is the correct list number for a 650 not all gaskets have the same holes

Yeah, I think the idle screws are okay, don't think there are any vacuum leaks, because the problem is intermittent. Will try the two hole wire trick.

I have seen the lower o rings in the float valves tear enough to restrict fuel flowing into the bowl when the car dies the residual pressure fills the bowl enougn to start only to stall again. remove the needle and seat and replace or closely inspect for any damage/foreign material.

If you have ever monitored the fuel pressure at the exact moment the motor dies and it is OK, disregard the following.
It has happened from time to time that a piece of debris will clog the fuel pick up in the tank. When the motor dies, the suction is relieved and the piece of debris falls away from the pick up and the motor will start right up again and will run until the pick up is clogged again.
Just food for thought.

Toby, that has happened to me too in my van. A bunch of rust kept clogging up the pickup tube screen, and the engine would stop. After some time, the rust settled back down and the van would go again, only to stall moments later. This was on a road trip no less, so I had to actually have a shop remove the tank and clean it out. $$$$$ This alos placed and excessive load on the mechanical fuel pump, and I buggered up a brand new pump as a result (first thought when the engine first died). This also brings me to another possibility. I know that failing fuel pumps usually don't function at high RPM, but I have had some that work fine above 2000 RPM, but at idle will barely pump and as a result, the engine dies after idling for a few minutes (again on a road trip with slow moving, construction-halted traffic, that was fun, yeah http://www.camaros.net/forum/rolleyes.gif )