4150 idle and hard starting problem.

[Mr.428]

The engine has a hard time starting, and it makes slight popping noise through the exhaust when idling. When I rev the engine up it will go down to about 1400 RPM stay and then slowly go down to 800 RPM instead of returning back quickly and it'll stumble and almost die when revving up. I've got the idle mixture screws 2 1/2 turns out 68 primary and 72 secondary jets, pink pump cams and size 35 pump nozzles.

[Gaz64]

2.5 turns out says the idle circuit is lean.
Is this a 2 or 4 corner idle carb?
What is the list number of the carb?

[Mr.428]

It has two corner idle and the carb number is 4777-5.

[Gaz64]

650 double pumper. What size engine do you have?

[Mr.428]

Ford 460 with manual transmission.

[Gaz64]

What's done to the engine, heads, camshaft, etc?
Carb is a bit small for me, my choice would be at least a 750.
Your idle circuit is lean if you need 2 1/2 turns out. Gary

[Mr.428]

Engine is stock except for the Weiand Stealth intake, which I installed. I did have the double pumper almost dialed in when I had the stock intake on it. I torqued down the intake properly and torqued it down again after I warmed it up. When I bought the truck the engine came with Holley 83310-1, and it was running real rich and fouling out spark plugs, and I checked for vacuum leaks around the intake & carb.

[Gaz64]

So the carburetor was OK on a stock intake, and not hanging at 1400, and now does this after the Stealth swap? Gary

[Mr.428]

Yes, correct.

[Gaz64]

Can you check both throttle shafts are on the stops, and then fit a vacuum gauge, then run the engine and report back with what the engine is doing? I'd also observe the ignition timing while this is happening.