I have a 77 280 with round top su's. this car has ben sitting for a couple years. i just went through and tuned it up and all that. the car is about 1 hr from my house now and i am tring to drive it back but the carb is acting up. right when it starts it revs up to about 2500 rpms and stays there till i mess with the gas pedal. it will drive fine for about 15 mins then it will start to bog down. i will be at highway speed and it wil just start bogging down. if it hit the gas it boggs down more. if i let sit for a cople mins it will run a little better. is there anything i can do to the carbs on the side of the road to get them working better? thanks for your help

 

Just Take A Screwdriver And Adjust The Idle As Needed Until You Can Get Home And Other People Time To Respond..

 

SUs have variable venturies. It's likely one of them is stuck. Remove the air cleaner and see if they move up with your finger and drop back down smoothly. If you have been running with out an air cleaner they get gummed up. Spray some carb cleaner on them and gently work them up and down. They should drop down easily by them selves. When you sart it they should rise gradually as you rev the engine and drop back down smoothly. There is an oil reservoir in the top of each one with a little dip stick. Make sure you have 20 weight oil to the mark.

 

thanks will try,

 

The fact that the engine was running OK then after being at speed it starts to loose power. Is this correct ? If so check the gas filters sounds like the engine is starving for fuel. There should be one filter near the tank and another in line under the hood. They are inexpensive I would change them both. There are screens in the fuel line where the fuel line enters the carb . At least they were there in the beginning . If you still have them toss them . your 280 should love the SUs and make good low end power to red line . When all is in good order . All the best. Gary P. S. the idle adjustment has nothing to do with this symptom it only impacts the speed of the engine when you let off the gas peddle.

 

hello my name is nick and i own a 81 280zx. i put a 77 block bored .10 over with flat top pisons and a port matched e-88 head (dont know what cam?) 1977 trans 4-speed and wanted to know if i should use 3 or the 4 screw domed top s.u. carbs? i have many other mods. any suggestions

 

Nick , first off start your own thread . This is hi-jacking this one. 4 screw and 3screw carbs provide the same performance.