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76 cutlass supreme - carb?


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i just picked up this car and i've replaced the belts, battery, plugs, cap, wires, oil change etc. while all of this has added a bit more pep, it's still got a sort of rough idle. i was wondering what it could be. any ideas? I just got this beast and i'm just trying to make it run... better.

thanks in advance!

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A rough idle could be any number of things, always start with the basic engine before you start looking at fuel delivery or ignition issues. Remove all spark plugs and do a "dry" compression test on every cylinder. For the most accurate results, hold the throttle wide open while cranking. Got a low compression from one or more cylinders? Next preform a "wet" compression test using a squirt of oil in the low cylinders. Compression goes up?? you have a ring problem. Compression does not go up?...'ya got a valve problem.

Good luck,

Dave in denton

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First thing that comes to mind is the EGR valve. It can be removed to clean deposits out of the passages. You can try disconnecting and plugging its vacuum hose for starters, and if idle improves, well, a lot of 70s cars have BB's stuck in the vacuum hose to disable it.

What did you set plug gap at? If the underhood emissions label spec'd .080 gap (early production HEI spec), reset the plugs to .060 or even .050 and see if you don't notice an improvement. This was a midyear factory change.

Next thing is a lot of cars just idled poorly back then due to all the emission stuff that was ladled onto them. Carburetion was very lean, underhood temps were hot, lot of things that adversely affected driveability.

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this EGR valve... i know it's the exhaust gas recirc... but what plugging it/not plugging it going to do? I'm just wondering... I don't have any experience with it, but i'll check it tomorrow after duty and post some results.

the reason that i thought it could have been the carb is because some of the arms that look like they would hold the slots open aren't very taught at all, instead they're kinda floppy, to the point where under the right circumstances it could possibly just kill the engine.

thanks for the help!

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  • 4 weeks later...

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