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Old 04-13-2006, 11:32 AM
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Rich idle on a Holley - what to do?

I did some searches but couldn't find what I was looking for.

I have set up my 350 in my 48 Ford PU to run pretty well. I finally got the idle straightened out, but it required turning the idle screws out to give the best idle in gear.

However, now it smokes a fair amount. I wouldn't say a lot, but more than I like. It's a Avenger 670 carb, put a 4.5" PV in it, 66's front, can't remember rear, but that shouldn't matter. The cam is a 292H Comp hyd., 244, 244 @050

Anyone have any ideas how to lean the idle out while keeping a healthy idle in gear?

If I just try to lean the idle mix screws, I start having problems with the RPMs dropping drastically when it goes into gear. The carb does have holes in the primaries, which I did based on some advice without really researching. Could that contribute?

Thanks for any help!

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Old 04-13-2006, 12:01 PM
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carb

What is your initial and total timing???

Do you know what the static compression is of your engine??? have you ever done a compression test??? If so what are the numbers???

Keith
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Old 04-13-2006, 12:15 PM
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And converter stall.
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Old 04-13-2006, 02:52 PM
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Initial shows 15 plus 21 from the HEI. I'm running vac. adv. that gives me a total of about 32 degrees initial.
C/R is 10.5
Haven't ever done a compression test on this motor.
Stall seems to be around 2500, probably just a little over stock. I don't actually know what it is. I had the trans. built a while back, and the converter came with it. 700R4 trans., hydraulic lock-up.
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Old 04-13-2006, 04:11 PM
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Put a timing light on it idling in neutral. Then have someone put it into gear while you are still watching the timing. If the timing drops you may have too soft of advance springs in the distributor allowing it to start advancing early, at idle when not in gear. When you put it in gear, it slows the engine enough to allow the timing to retard making the engine slow even more. Stiffer springs keep the distributor from advancing early, giving a more stable idle.
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Old 04-13-2006, 04:26 PM
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is your vac advance routed to a port or manifold vacum source?
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Old 04-13-2006, 08:12 PM
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Does the distributor have vac advance only or both vac and mechanical. I usually have the best luck tunning the idle circuits with the vac advance disconnected so the distributor sets on base timing. Where in the throttle plates did you drill the holes and what size hole did you drill? Do you have a PCV valve hooked up. No PCV valve can make it idle rich since a PCV valve is like a vacuum leak and the carb is usually jetted to compensate.
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Old 04-14-2006, 08:17 PM
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Vac. adv. is routed to manifold vacuum. Have the Crane Came adjustable adv. can. with it all the way loose (lowest vacuum pegs it).

The holes I drilled in the front side of the butterly, I believe 1/8" dia., about in the middle of the half if you get my drift. do have a PCV valve hooked up.

Good point about the mechanical advance - I will check that out. I don't even know what RPM it's all in at, but it's easy enough to find out.

BTW, it smokes out the pipes in gear and out of gear.

JLutz - are you thinking that the timing is falling off enough to cause me to compensate by richening the idle mixture? I suppose that is possible. It would seem that if I'm running at around 35 BTDC at idle, that a couple of degrees due to centrifugal wouldn't amount to much - but I guess I don't know that it is in fact only a couple of degrees.

THanks for the help.
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Old 04-15-2006, 07:20 PM
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I was asking about the timing because timing can be fairly critical in obtaining a stable idle and you said it tries to go dead in gear when you lean it out. I would try unhooking the vacuum advance and see if you can get a stable idle. I believe it should be hooked to a ported vac source anyway so that it really doesn't get signal at idle. You see if you lower the timing at idle, it will make the RPM drop so you compensate by turning the idle speed screw (throttle stop, not mixture) in a little opening the throttle plates. This allows more air through around the plates and less rich mixture through the idle circuit. The idle circuity provides a purposely rich mixture, because it is designed to mix with the air bypassing the throttle plates and air coming through the pcv valve. If you have the idle screw backed out to get the RPM right with 35 degrees at idle, the plates are probably nearly closed and almost all of you mixture is coming from the idle circuit alone. That is why when you lean it out, it dies in gear. By turning in the mixture screw, you have effectively cut off nearly all available air and fuel. Try pulling your vac advance to reduce the timing at idle and idle it back up with the idle screw. This should lean it out a bit, If you will notice, most production cars idle around 5 - 10 deg BTDC because it allows the throttle plates to be open farther and the RPM still to be in check. Race cars sometimes have fixed timing at 35ish degrees, but they also idle fast.
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Old 04-15-2006, 07:22 PM
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Also check fuel pressure and float height. I had a 68 camaro that flooded at idle and it had too much fuel pressure, so it would overrun the float and it had a stock appearing mechanical pump.
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Old 04-15-2006, 08:09 PM
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With that much duration, you may have to either put stiffer springs in the distributor, or lose the manifold vacuum and go ported vacuum. I had to do the same thing, and chose to go to the ported vacuum. Now, not too much drop in rpm between park and gear, and able to idle just fine. Hope this helps.
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Old 04-15-2006, 10:51 PM
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We used to, and still do lean out idle orifaces with this method.

Pull the front metering block off the carb and look at the body side of it. There will be two long passages on each side of the block, top to bottom. One each, on each side, will have a large drill home, the other ones will have a small brass 'jet" in it, at the bottom of the passages, almost directly adjacent to the center of the power valve. These are the idle jet restrictions.

I take one strand of a section of copper wire and bend it into a U shape, then insert one side of the U into the large hole, the other into the jet oriface, closing its diameter down. Different guage wire strands will restrict the ortigace less or more. The U shape and metering body gasket will keep the wire in the jet when the block is replaced onto the body.

Try a strand from a 14 guage wire to start with.

This is one of the areas I have issues with, with both Holley and BG carbs, as these idle jets should be changeable, with sized changeable threaded orifaces, just liike a selection of main jets and air correctors, supplied with the carbs.

In the past, when I wanted a greater range of tuneability from these idle orifaces than what I coould do with the strands of wire, I pulled the fixed orifaces out of the block, tapped the holes for Allen set screws and drilled a few sets if screws with different sizes, making them into replaceable, changeable "jets".
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