hey! new to the forum so parden anything i say that isnt worded correctly, so ive got a 73 plymouth valiant with the original slant 6 225, car had a rebuilt engine back in 03. i bought the car from an older gentleman who let the car sit all that time. the car had 900 miles on it and i got it in may of 2015. the car was running totally perfect, some mechanic friends suggested i start replacing little things here and there as i wanted to up the car to be a semi show car. i want this to be a clean car. replaced the electronic ignition, ballast resistor, cap, rotor, plugs, wires, air cleaner, breather valve, tranny fluid change, oil change, timing is set at tdc, carb rebuild, and the car seems to want to run like garbage... idles fine but with any rev it acts like it wants to drop WAY below the idle rpm. ive tried swaping back to old parts that were working find to see if maybe a new part was bad, but nothing is working to fix the problem. the car starts, idles fine, drop it into gear and you get some stumble, drive up the street and the stumble goes away, try to hit the brake and it acts as if youre hitting the break in a manulal without pushing in the clutch. any suggestions? this thing is suppose to be my daily and was doing great before some supposed good updates

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73 Plymouth valiant/rat

You broke a cardinal rule, don't change too many things at once. You changed a lot of components under the hood all at once.

My suspicions are around the rebuilt carb though. Maybe you have a vacuum leak, or the carb is flooding out, not adjusted correctly? Did you rebuild the carb or buy a rebuilt carb (Dan will tell you, these are often junk).

When you do figure this out, make sure not to change out a bunch of stuff all at once, do it one piece at a time to make sure each piece is OK before moving onto the next piece.

I'm sure the folks on this board can help you figure it out.

Brian

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https://tinyurl.com/yynpj4v2

This sounds like a nice car...just curious.

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https://tinyurl.com/yynpj4v2

Carburetor operation and repair manuals and links to training movies and carb repair/modification threads are posted here for free download. Tune-up parts and technique suggestions in this thread. Get the three books described in this thread and start readin'!

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

+1.

Sounds like your idle speed and mixture are incorrectly set, I doubt your timing is supposed to be at TDC, if you have power brakes you *MIGHT* have a failed brake booster (fix the other problems before investigating this one).

TDC sounds suspect, but I'm betting on carb issue/vacuum issue.

b

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If you have power brakes, disconnect vacuum line to booster at intake manifold, cap off vacuum tap at manifold, and see how it idles. If you drive with booster disconnected brakes will have a mushy slow to react feel, be very carful. I would limit test drive to driveway where problem is at idle rpm and when coming to a stop.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

the car was running well with all the new parts added, i wanted to do the proper tune up so the car wasnt running in a bland state. adjusted timing and the carburetors to spec then adjusted as needed to get a proper idle at 750 rpms. the car is doing fine at an idle but its not looking so hot when youre actually driving it. no on the power brakes as the car does nit have a brake booster.

could the carburetor rebuild be bad? if so ill look into either a new carburetor. some friends said to check the spark plugs for actual spark and to investigate the fuel pump being bad?

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73 Plymouth valiant/rat