Holley carb parts swapping question for the gurus

I have a Holley carb that is OEM out of a 85 E150 van. It has no provision that I can find for idle air mixture adjustment. Would it be just a simple matter of replacing the existing metering block with one that has metering screws or are there differences in the main body too? I know some Holley idle air systems work backwards during the smog years. What type of metering block should I look for if this swap is possible?
Kywookie

I wouldnt do it, the air bleeds in the body need to match the idle feed restriction in the metering plate. It may work, but you'd be better off trying that carb as is, or tossing it and getting a 600

I tried mixing blocks from one carb to another and it was never right.
[addsig]

The air mixture screws are in the base of the carb under the fuel bowls......dont change the blocks becasue it will not work, 2 different animals..........Take carb off and grind out the caps and you will see the screws in there........Its a real bi*** to adjust when on if not impossible.........Jesse @ BIGS!![img]/phpBB/images/smiles/icon_frown.gif[/img][img]/phpBB/images/smiles/icon_frown.gif[/img]
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On 2004-08-23 20:34, BIGS wrote:
The air mixture screws are in the base of the carb under the fuel bowls......dont change the blocks becasue it will not work, 2 different animals..........Take carb off and grind out the caps and you will see the screws in there........Its a real bi*** to adjust when on if not impossible.........Jesse @ BIGS!![img]/phpBB/images/smiles/icon_frown.gif[/img][img]/phpBB/images/smiles/icon_frown.gif[/img]

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So this one of those backwards adjusting smog carbs? The carb sits so close to the intake that I can't even see them under there. Since they weren't intended to be adjusted I guess they didn't care about accessibility. Ah hell, manufacturers nowadays don't give a flying crap about accessibility anyway. I'll have to search again tomorrow. Thanks to all for the info.
Kywookie

Well, it IS meant to be adjusted, but only with a typically complicated OEM procedure that sometimes called for weird stuff and extra equipment (like propane hookups). Then you snapped on the caps so someone else couldn't tweak the carb. The caps are there because you set the carb per OEM SPECS PERIOD and NOT to RUN RIGHT during those times. You sometimes could get them to run OK, but that meant tossing the setup procedure, which screwed up the emissions profile. But typically, they were just crap. I sold Holley Economasters during the dark days of performance - those were junk too. Pitch it and get a real carb. And don't try to mix the parts - likely it still won't run good and you'll never fix it.
[addsig]