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Sounds like it is leaning out. This could be either running out of gas or a vacuum leak.
Do not know if possible, but I would like to bolt on a known good carb and see what happens. If you have any vacuum lines coming off the intake or carb base, this includes capped tubes, put your hand on them. Twist them around and make sure they are solid with no cracks.
Looking more and more like intake gaskets. I hate to go there without trying another carb. Keep me updated, good luck.
I cannot imagine you are pulling enough air around the rear throttle shaft, but you can put some heavy grease around the shaft, where it comes out of the base plate.
 

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You can check for a vacuum leaking with a squirt bottle filled with water. Set the nozzle to a stream and with the engine running spray water around the intake runners, carb base gasket, etc. If there is a leak you will see and maybe hear the water get sucked in. If it really is that lean you might keep the engine running by putting your hand over the primary side of the carb to restrict the air going into it. You might be able to close the choke a bit to do this. I did this lots back in the day.
Good luck.
 

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Discussion Starter #23
I'm waiting for a new throttle plate for the Holley to try these suggestions. Not sure how long till it gets here. I don't have many gearhead friends that would have an extra carb laying around, although that would surely eliminate or confirm whether that is the problem.
 

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Discussion Starter #24
Well that was the best $140 I've spent. Got the throttle plate today and what a difference it made. Got everything back to normal. Got a good solid 750 idle. Set my idle mix screws with the vacuum gauge and set the fuel levels. It is great when things do what they are supposed to. Vacuum is at 13 at idle.
So like I mentioned, the secondary throttle shaft was wobbly on the old one so that left some air in, but I think the biggest improvement came from the new throttle base. I know from taking a 6 inch scale across the base I could see a slight amount of daylight. I thought at the time that the gasket would take that up but now I'm wondering if it did.
So thanks for all the info, glad I didn't have to go deeper.
 
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