I think my carb is fudged up.

Reasons:
Can't get idle above 10 and keep good drivability.

Setup:
85 f250 a axle and a door in the rear 3.55 zf5 33" tires.
Engine:
10:1 bored .05 390 pistons 1.76 rollers rv cam head work Clifford intake Herman headers
Carb:
Quick fuel slayer 600 mechanical secondary.

What has been done:
Idle air bleeds went from 70/72 to 76s. Bumped it 10 or so. But had a lean spot so resetting the 4corner idle put it back to 9.8 or so.

Can get it to idle at 11.5 with floats down, and cruise at 16.

Went to 85 idle air bleeds and sane thing.

Called quickfuel. Said to drop my idle restrictions from 31( assuming it had 31 in there) to 28. No change in idle aft, not it runs richer cruising and leaner at bigger throttles(more then half way)

I also changed my squirters to 31 from 28 and that also made it run a little richer at cruise so it could just be that.

My accelerator pump needs a bigger shot, cruising then a smash shoots it up for a second or two and then comes back down.

Wot pull goes about 16 also. I think the accelerator pump has to do with that.

My next step is to call quickfuel and see if they can check it out and see any cracks, or issues. If not then I guess I'll try the new Street demon out?

Ask any questions but I'm really about to just sell it. I love the car and the way makes my engine run but I can't do this 9.5 afr. That's too rich. Hurts my oil, leaves clouds, and I know I can get some decent mpg out of this. I'm at 2100rpm in 4th doing 60

 

Honestly, that sounds like something is wrong with the carb. With that much tuneability, you should be able to put it right where you want with a few adjustments.

Your idle AFR should be set by just the idle mixture screws. If they don't do it, there are the idle feed restrictions inside your metering block.
The idle feed restrictions also affect your cruising AFR, since you aren't always on the main circuit (the main jets) while cruising.

Changing your Accelerator Pump Squirter should have no affect on your cruising AFR. None. Those only come in to play when you push on the gas pedal, since they are activated by the movement of mechanical linkage. If your foot doesn't move during cruise, nothing should come out of them. That's really strange if it did change your AFR.
Maybe you have too much air moving through the carb and you need anti-pullover squirters? These are designed for the situation where the airflow through the carb has enough velocity that it actually pulls fuel up and out of the accelerator pump circuit during cruise.



https://www.holley.com/products/fuel.../parts/121-231


Otherwise, you should really be able to dial that puppy right in and have a great running engine. Something is amiss, and it doesn't sound like it's just the choice of jet sizes.

 

I changed everything that controls idle to get more air and got no where. That's why I'm lost. I understand that the squirter thing is at a constant pedal, but I've got hills and passing and all of that that isn't a perfect same pedal spot so a smidge here and there just does more dramatic things now. And I run lean when I push the pedal down enough to use the diaphragm.

I'm about to call them and see.

 

Are the secondary throttle blades closed at idle? How much of the transfer slot is showing on the primaries - they should look like a small square at idle.

I would also wager you'll need richer jetting to make up for the slow airflow when you mash the gas on a mechanical secondary carb. Even at 6,000 rpm a 300 will only draw 350-400 cfm so if you stomp on it at 1,000 rpm airflow through the carb is going to slow dramatically. How far are the primaries open before the secondaries start to open?

A mechanical secondary carb on a non-race vehicle will be hard to dial in from idle to WOT. Especially if it's too big for the engine.

 

I completely missed that you said it's a mechanical secondary.

 

Dylan, everyone on the forum has been frustrated as you now are and knows that pain.

Is the fact that it is new preventing you from pulling it apart and cleaning it and blowing air through all the tiny passages and throwing a gasket set on it?

My 1848 was new, and I had to do it. Sometimes a tiny piece of grit can get in there and drive you over the bend. You may be only a day of work away from perfection. I hope you get it corrected.

Love your trans. I have one sitting on a dolly ... waiting.