New (to me) carb, way way too rich

[Gene King]

Hey guys,
I put a 650 cfm Holley 1850-2 on my 305 'cause thats what I had to replace a feedback quad. It's running incredibly black smoke rich though. I know it's a little bigger than ideal but this is an eye scorching situation. It's got 1 metering block with #66 jets right now, single pump, 6.5 power valve. I disconnected the vac diaphragm which should make it like a 2 barrel I think without any improvement. I started the idle screws at 1.5 turns out and turned them in until they were 0.5 turns out without any major improvement. Float level is set towards the lean side, it's below the sight plug
Anyone with more experience based on this able to tell me if I'm dealing with a carb malfunction or just gross mismatch of carb/jet and engine size? Thanks

PS. It's a stock '86 305 otherwise

 

[82sbshortbed]

Dam holleys! I wish I could help you out but, I run quadrajet on mine. There's plenty of holley lovers here tho that can help you.

 

[Gene King]

I might be honing in on it, the secondary barrels were wet

 

[Ricko1966]

Is the pcv valve hooked up and working?It's not due to carb size, it is possibly a blown power valve, that used to be a real common Holley failure. How much vacuum do you have at idle?Do you have any big vacuum leaks?Is the throttle stop screw turned in too far ?These are things that pop immediately to mind and I would check. Your qjet should be a dual accelerator pump model, not feedback. Personally I'd clean it and put a kit in it it's a very carbureator.

 

[Gene King]

Yea PCV is hooked up. That's interesting about the power valve, I hadn't thought about it since I've never had a holley. I'll check that tomorrow, my vac gauge is MIA I'll have to hunt that down.

You're right about the q-jet, it's got a broken auto choke housing and a linkage issue so I didn't look at it close before, but I took it's top off and the electronic portion is a second accel pump. That would work for me too but I'm gonna try to diagnose this holley since I already have it all setup and I think you put me on a good lead.

PS thanks for the help

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[Gene King]

No luck finding any problem with the power valve, I was taking apart a matching carb though and noticed my first one is missing a piece. A thin sheet metal backing to the metering plate

 

[hirschdalechevy]

That thin plate is to support the metering plate across the power valve cavity in the main body , so with out it you could have an internal leak on the secondary side. Some main bodies dont have that cavity and then you dont need that thin plate.

 

[Gene King]

I just came back inside from trying it out, works mint with that plate installed. I do have a power valve cavity on the secondary in both carbs, the manifold vac port on them is just filled up. Never occurred to me a piece was missing, guess I learned a lesson to look at an exploded view. Thanks