I was having problems with the engine idling sporadically on my 292 with 2 bbl autolite and fordomatic transmission.



I bought a used carb from a 352, soaked it in carb cleaner overnight and rebuilt it. The jets in the 352 carb were 55 and the jets in the 292 carb were 46 so I swapped them when I rebuilt it. After soaking the carb, I ran a wire through each passage and sprayed each passage with spray carb cleaner and then compressed air. I put the carb on the engine and it fired up nicely, it has a rough idle, but runs great other than that. I tried adjusting the idle after the engine warmed up and the choke was wide open.



The driver side adjustment can be adjusted all the way in. It still runs, but not as good, and sounds different. The passenger side screw can be adjusted all the way in with no change at all. I can also adjust both screws way out past 1.5 turns with no change. I sprayed wd 40 all around the base with no change. I also sprayed it around the throttle shafts with no change in idle. The transmission shifts fine.



Does anyone have any ideas of why my idle screws don't seem to have much affect on the idle? Thanks.

Dave Coleman

1962 Country Sedan

http://www.62ford.com/

On a Holley, it can indicate a bad power valve. Do Autolites have power valves?


Lawrenceville, GA

Yes, it has a new power valve that came in the carb kit. The carb kit is the same for a 352 carb and a 292 carb, so it is the correct power valve also.

Dave Coleman

1962 Country Sedan

http://www.62ford.com/

New does not always equal good. It wouldn't hurt to check it.



Another thought, because the carb was originally for another application, maybe the throttle plate is open too far in order to get the desired idle rpm and activating the main circuit, in which case the idle screws will do little.


Lawrenceville, GA

How do I test the power valve?

Dave Coleman

1962 Country Sedan

http://www.62ford.com/

Dave, there are several iterations of the Autolite 2 bbl so randomly swapping applications may cause some problems.  I have also found some kits are not very good.  I recommend only NAPA/Echlin or Standard Hygrade kits.  There may be other good kits but those are the ones I have had satisfactory results with. It does sound like the power valve is either blown, not installed properly or the wrong vacuum value.  There are about 6 commonly available power valves.  Each has a number stamped into it that identifies the vacuum at which it opens.  Examp. "65" = 6.5 inches of Hg (mercury).  A number 65 is stock in most applications.  Check the float level.  Hopefully the float valve in your kit is Viton tipped.  The plain tipped ones often leak.   A good fuel filter is also essential.  Be sure that there are no vacuum leaks elsewhere.   Good luck and let us know what you find.

I decided to rebuild the original 292 carb (for the third time), and use the best parts from both carbs with the exception of the jets and venturi assembly, which I used from the original carb. I thoroughly checked every circuit to make sure they were all clear. I also sprayed carb cleaner through every circuit and every air bleed, etc. I made sure the throttle and choke plates were closing correctly, by loosening the screws that hold them in place and wiggling them while closing them, and then tightening them in place. They all close nice and flush. I made sure the float level was correct. I used the power valve from the 292 carb which had a new power valve put in a few months ago. I put everything back together and the car runs great. It has a fairly nice idle and and no hesitation when punched. But, when I went to adjust the idle, I can screw both idle mixture screws in all the way, and when I do the engine speeds up and appears to smooth out a little more. When I adjust them back out some it runs rougher but not bad at all. When I continue to adjust them out further than 1.5 turns, all the way to 3.5 turns, it doesn't get any worse... just stays the same. I don't know why adjusting the idle mixture isn't doing what it is expected to do, or if I should even do anything about it because the engine runs so good as it is. Any ideas?

Dave Coleman

1962 Country Sedan

http://www.62ford.com/

If  you can seat both idle mixture screws and it keeps running the carb is drawing fuel from another circuit.Possibly you have a vacuum leak somewhere.After doing the carb twice with no improvement you need to look again for another problem.Try squirting some quick start around the intake and carb mounting.If the idle speed increases you have a vacuum leak.If the idle speed screw is holding the throttle plate open more than about 1-1 1/4 turns after the screw  contacts the throttle plate lever you are drawing fuel from the transition circuit which comes in after you leave idle.When you start drawing fuel from the transition circuit the idle mixture screws have no effect.Excessive throttle plate opening is another indication of a possible vacuum leak.

  

It sounds as though the engine is "idling" on the main circuit.  Note that if the throttle blades are too far open the idle ports will not be exposed to enough manifold vacuum to function properly.  Fuel will flow from the boosters and circumvent the idle system.  Also, the booster venturi has a fixed idle air bleed orifice built into it which is application specific.  You changed that and altered another parameter.   If possible, verify manifold vacuum at idle with a guage.  If it is low, < 10" of Hg, you will need to determine why and correct that before you can proceed with the carb.

Just a thought on the power valves. Sometime people will install a power valve from a Holley in an Autolite carb. While it will screw in ok, it may only work for a short time if at all. The difference between the 2 is the Holley has a recess where the gasket seats and the Autolite is flat. In the end the gasket doesnt seal & it leaks fuel like a blown power valve.

Dan      Kingman Az.      86409