Holley 750 Questions

Did you change any thing sense the other guy had it.  
professional hi-performance engine builder

Horsepower sells engines and torque wins races

No the other guy that had it left it sit for 6 years. When I got it and had this trouble I took it apart and cleaned the whole thing with carb and choke cleaner.  

Wow 6 years it probably has a clog some were and possibly in need of a rebuild.
You may have to soak the metering blocks and plate in carb. cleaner and then blow out all the holes with compressed air also remove the mixture screws and make sure there not blocked also.  
professional hi-performance engine builder

Horsepower sells engines and torque wins races

Hi after further diagnosing I found 4 of the 8 cylinders are not firing. When I had it running I started pulling spark plug wires off 1 at a time 4 of them seem to have no change in engine Rpm. The spark plugs had spark when I set them on the valve covers. I think the valves are sticking or not seating causing the cylinders to fire. That is probably my suspected carburetor problem not having anything to do with the carburetor at all. Please let me know if that sounds possible. I just thought the engine had a radical camshaft no mufflers on it right now.
        Dave  

Ya it is possible but I do not think it is what is causing the problem.
What does the 4 plugs look like on the the cylinders that do not change the rpm when you remove the wires from them.
Also if you pull the valve covers a rotate the engine you should be able to tell if the valves are stuck or sticking.  
professional hi-performance engine builder

Horsepower sells engines and torque wins races

I pulled the valve covers and everything seems to be working. The pushrods are pushing the rockers and the valves. I talked to a local mechanic who said the valves may not be seating do to rust. I am going to do a compression test next. The plugs on the cylinders that did not change rpm are black little wet.  

That is why the RPM's did not change because the plugs are fouled.
Yes do a compression test and let me know what the readings are.  
professional hi-performance engine builder

Horsepower sells engines and torque wins races

The plugs that were in those cylinders that were black were sparking when I set them on the the valve covers and started the engine. I just replaced all the plugs the other day with new AC's. I did check timing too at 3000 rpms I had 35 deg. total.
   I am stumped!  

Ya but it is probably not a hot enough spark to ignite the fuel properly.  
professional hi-performance engine builder

Horsepower sells engines and torque wins races

Do the compression test and post results.  If your getting a spark to all 8 cylinders in the correct order at the correct timing and with new spark plugs, then your problem is not ignition related.  In which case it is either air/fuel mixture related or a mechanical problem in the valve train or bottom end.  Do the compression test to further thin out the possibilities.  
1969 GTO, YS code 400, 350hp/445 ft lbs of torque (stock specs), LT headers, H-pipe, 750 Holley 4160, Ignitor II ignition.  Complete Painless wiring.

Hi I am going to do the compression test soon. I am trying to round up a compression tester. Right now I am trying to get the car primered before winter. I am still not sure if the carburetor is any good either.  

I came across a deal on two quadra jets carbs for $35.00 with new rebuid kits too. I put the one on and now my rich problem is fixed. The motor idled good with no black smoke even when I rev it. I also talked to the guy that had the car before me. He told me he bought the Holley brand new at advance auto parts put the carb on but never drove the car but from what Holley tech told me the base plate was warped must have been a bad carb. The engine still makes no difference when I pull off four spark plug wires. My dad talked to a mechanic today he told him the spark plug wires is the problem so I ordered some new Accel wires he also picked me up a compression gauge at a yard sale today for $4.00 now if the problem is still there after the spark plug wire change I will test the compression.  

The problem is when ever you have a carb. that has had gas in it and then you let it sit for 6 years the carb. will go bad and not work properly.  
professional hi-performance engine builder

Horsepower sells engines and torque wins races

Ya I know I did take it apart and spray carb cleaner through all the passages and circuits. What else could I do. I don't know. The thing that got me is when you screw the air fuel mixture screws the whole way in the engine stayed running. Thanks for your input.  

If you screw in the idle screws and the engine stays running the carb has an internal fuel leak, probably through the blown power valve.  It's dumping raw fuel into the engine.  The carb needs a full rebuild and a power valve.  
1969 GTO, YS code 400, 350hp/445 ft lbs of torque (stock specs), LT headers, H-pipe, 750 Holley 4160, Ignitor II ignition.  Complete Painless wiring.