I have a 56 Ford Fairlane with a 292 Y-Block, Holley 600 carburetor and a Fordomatic automatic transmission. I’m having trouble getting it to idle in both Park and Drive. When I set the idle properly in Park or Neutral and then I shift it to Drive or Reverse the RPM’s drop off to ½ of what they were and it'll barely run. And when I move the idle up to get the car to run in Drive or Reverse and shift to Park or Neutral the idle goes up to double what it should be. I’ve had 2 different Holley carburetors (1 was a warranty replacement) and 2 different sets of ignitions components. Local transmission expert tells me it can’t be the Fordomatic. Any ideas?

Is the 292 stock, otherwise? Does it have the stock distributor?


Lawrenceville, GA

I had the same problem with a 390 Holley.First step is to take the carb off and turn it over(after emptying the gas in the float bowls).If you look at the throttle body in the area where the butterfly closes you will see a slot in the throttle body.This is a "transition slot" which allows fuel to enter as you leave idle such as starting away from stop position.With the butterfly closed you should only see a "square"below the throttle plate.If you have much more than that exposed too much fuel enters at idle and you will never get a satisfactory idle in drive.Back off the idle speed screw until you have just a square visible below the butterfly.Make a note to yourself how many turns of the speed screw ÄFTER the screw contacts the throttle lever to get that preferred position of the butterfly.Mine was about 3/4 turn.If you start adjusting the idle speed and lose that position while doing so you can start again without taking the carb off.When you reinstall and start it he idle speed should be about right with maybe a small adjustment.If you turn it too far you start to draw fuel from the transition slot which cannot be controlled by the mixture screws.Than you are back where you started.I know exactly the impulse to turn the speed up.If you cannot get a proper idle speed with the throttle plate in preferred position and mixture screws about 1-1 1/2/2 turns out from closed position you likely have a problem elsewhere like a vacuum leak possibly.Also check the float levels to be sure  fuel is not  dripping into throttle bore.If you have a stock motor like mine you should not need to try the following suggestion.The secondary plates also have a provision to open them a little at idle to allow more air in.If you have the carb off look at the base plate below the secondary throttle.Should be a threaded hole which would take a threaded screw which can be used to hold the plate open a little for air to enter.Sometimes with a hipo motor holes are drilled in the leading edge of the primary plates to allow more air to enter.Adjusting the secondaries does the same thing.Also bump your initial timing to a bout 10-12 BTDC if you have not already done so.Check the Holley website for more info on setting initial idle speed.They have illustrations also.Hope this helps.Been there before myself.

  

Thanks I'll try this....Yes it's a stock 292 with what I think is the stock distributor (it has duel vacuum advance). And I bumped the timing up a little and it seemed to run a bit better!

If you do a search using the search topic at the top of each page on 'transition slot" theres several previous discussions on this topic.The second or third one started by "Pops" has some illustrations about page #5 to clarify what I am trying to describe.If you are still using the stock distributor(which I think you are) a fairly inexpensice improvement is to purchase a later distributor for a 1964 F100 with 292.They can be purchased as a rebuilt unit through any auto parts supplier.You need a cap and rotor for the same unit as they are different than the stock cap.This gives a much more responsive timing advance based on engine load at low speed throgh the vacuum advance and at higher speeds using the centrifugal adavance.The existing distributor is vacuum only.Ford changed to the better dist. in 57.If you shop around for that dist they can be had between $50.00 -$80.00.Check around they are all from the same rebuilder.

  

Well, it may not be causing your problem, but you need a distributor for a 57 or newer Y with that carburetor. For the time being, to eliminate the advance system as a cause, disconnect the vacuum lines and plug the ports so there are no vacuum leaks. This will eliminate the ignition advance from the system and ensure that you're only dealing with static timing at idle.

Oh, and do you know if the car functioned properly before the 600 was installed?


Lawrenceville, GA

Charlie is absolutely right.I was just sitting here thinking about your question and the light went on when I realized you chenged carbs without changing distributors.The original will only work with the original carb which has a special spark advance valve built into the carb.You wont get any advance at all using the  old dist.If you use the application I mentioned 1964 F100 with 292(the last year in N.America the y-block was used) you can get prices calling around.

  

this photo shows the old style distributor - it has to have the old '56 carb vacuum ports in order to work. The two springs on top of the point plate are a quick indicator.

The later one will be like below:

 
 Steve Metzger       Tucson, Arizona

This is the idle transfer slot that Mark is talking about. When this isn't set up right, Holley 4160 carbs will do nothing but fight you......

If it won't idle with the primary throttle positioned as shown above and the initial timing set at 10° before TDC - there is a small screw under the vacuum secondary operating lever to open the secondary blade a bit. Resist the urge to move the primary stop screw - no matter what. The one for the secondary is on the passenger side of the carb and screwed in from the bottom. Opening the secondary will add a bit of air to keep things going while you set the primary mixture screws for best idle speed (or highest vacuum).

In the old days - it was common practice to actually drill some extra holes in the primary throttle blade to get this extra idle air......don't. I usually put a longer screw up into the stop position and cut the head off to make it an "all-thread" - and then just turn it with needlenose pliers. Most intake manifolds and adapters have room for it to stick out on the down side.

Don't get fooled by having a free flowing entry through the PVC system - it can run up the idle speed by pulling air in through the breather. Plug it or get an orfice in there to restrict it a bit.

 
 Steve Metzger       Tucson, Arizona

Hi Steve! 56FairlaneAZ did not mention a PCV system but you are right to mention it.Part of my problem ,after I took your advice and setup the carb as you and I have explained here,was the PCV valve was too big.I went from one for a 302 Ford to one for a 4 cylinder Fairmont/Zephyr.Fixed the lean idle.I remember working on mine trying to get it to idle in drive.I thought at one point i had a convertor problem because when it was put into drive it would almost die.Put it in neutral and it was fine as 56FairlaneAZ has mentioned.Once I got the throttle plate positioned properly I was on the way to getting it running like it should.If(when)56FairlaneAZ gets the distributor we can help him get that setup like I did with mine(with your guidance).For about $6.00 it can be made to work even better.