So I can’t get it to run right I’ve tried 2 carburetors one runs like **** but revs still like **** but the second carburetor runs like a champ but when I rev it past 1200-1500 it backfires threw the carb sometimes shoots flames out. I’ve checked timing 3 million times I check for vacuum leaks nothing spark plugs were new but are now soaked in a matte black coating so I put new ones in and still does the same thing I got 2 videos im gonna upload with different carbs. Files are to big so I put em on youtube https://www.youtube.com/shorts/GUQzdvO5iF8?feature=share
https://www.youtube.com/shorts/7eiecvhpiGE?feature=share

 

You need to provide a lot more information. Backfires can have a few causes but I usually find it is a rich mixture and retarded timing causing a backfire
Sounds like you are running super rich or maybe burning some oil post some plug pictures

Is everything new if not what is used?
What 350 did you use? give a description of that internals and heads it has
What camshaft?
Did you build the motor?
What distributor are you using?
What is base timing?
Is the vacuum advance hooked up? Ported or Manifold vacuum?
Were both carbs new?
What was carb #1?
What was carb #2?
Did you try letting it warm up all the way?
Please post some pics of the motor

 

I bought the engine from a family member he’s a part of box performance in Ohio it’s a 1992 4bolt with a mild cam idk the specs and it has vortex heads it ran great in the last car it was in. It has a stock hei distributor, timing is set at 8 degrees, vacuum advance is ported, bothe the carbs were rebuilt I tried all the adjustments on the first one it’s a Holley 4 barrel, the second carb came off a 1985 f350 it was running great on the truck before it pulled it and yes I have tried warming it up does the same thing

 

Vortec heads ? Looks like swirl port does it run better with more initial advance ?
vacuum at idle ?

 

Was it running good in the car it came out of?...

 

I see a Holley built Carb for a Ford "Motorcraft" Engine.

Actually Holley built Carbs for many different companies...
There were quite a few GM Rochester Carbs built by Holley.

 

Yeah as Holley carbs go, that's about as pitiful of one as there is. But that's OK; it should still run plenty OK, just, maybe not as good in some ways, as some others might.

Backfiring out the carb is a symptom of being WWWWWWAAAAAAAYYYYYY too lean, or of intake valves being open when the cyl gets a spark. First thing I'd check would be, valve adjustment. Get the engine fully warmed up; take off the valve covers; start it up; back off each valve, one at a time, until it starts to clack, then tighten back up until it just barely quits; go through all 16 like that, as fast as you can. Then shut the engine off, tighten each one exactly one half turn, and put the valve covers back on. See if that helps. Might want to take it to the quarter car wash afterwards to clean up the mess.

One of 2 things will happen: it will clear up, or it won't. If it does, mission accomplished. If it doesn't, come back and we'll figure out where to go next.

 

Guys, try tracing his spark plug wires. There is no way he has them connected correctly - 18436572.

Edit: maybe I am wrong. This is what I was able to trace (WHITE numbers). Green are my guesses.

 

Great catch!!!


Unless the Distributor Cap has the Terminals rearranged... like some aftermarket Caps do, to try and neaten up the Ignition-Wires.