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mattchew

idle problem advice please?

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Hey so ive got a 73 240 with the 72 SU's with the emissions removed vac lines on carbs capped. only engine mods besides carbs is 79 electronic distributor, and electronic fuel pump. Well when I start the car it idles around 800 but after about ten minutes of driving the idle works itself to 1500 and doesn't come down from that. A friend told me it was was probably a vacuum leak because sometimes wen i turn the car off the engine runs for a second, and my heater vents blow cold air and defrost blows warm, and you can kinda hear a hiss from the engine when i turn it off that i cant find anywhere.... so I unplugged and capped the distributor advance and the brake booster but neither helps. I also sprayed starting fluid all over suspicious spots like intake and hoses. and only around the the throttle shaft where it meets between the two carbs did it seem to make any idle fluctuation. maybe this could be the problem? warn out? any help would be greatly appreciated:)

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Can you post a really good pic of the carbs and balance tube?

Is the 800 RPW with or without choke? Is the choke even functional?

The heat and vent temp thing is normal.

I think your not adjusting the carbs correctly. Set the idle speed at opperating temp.

Edited by 5thhorsemann

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I agree with the Horseman, you need to set the idle speed at operating temp. All tuning adjustments are suppose to be set when the engine is at normal operating temperature.

We have the same set-up as you (73 car with 72 carbs). The idle speed increases as the car warms up. This is typical of most carburated cars because the fuel/air mixture is too lean when the engine is cold and becomes richer as it warms up.

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ok thanks guys. so I ended up getting them tuned at ztherapy (Steve was a really nice guy by the way) and it ran better but long story short i still couldnt get it to run right. It had a vacuum leak at the throttle shaft like i thought. so I ended up pulling the S.U.'s from my 72 parts car. they were the same carbs of course but i went through them. I got really lucky, it runs like a champ now. I don't think i have much of a power difference but it runs way more consistent, better fuel economy, and sounds a lot better. now my idle starts around 550 without being choked and warms up to about 800. totally different car.:)

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