so, i have a holley 2300 2bbl.

tuned up the engine -new AC Delco spark plugs, changed the oil, the whole nine. (cap and rotor)

car ran fine for about a week


the car was always running a little rich, so we played with the mixture.

now it idles perfect, hardly any mis-fire. but when the rpms reach above 2500, i get loud poppping sounds coming out of the carb. the car won't accelerate pass 40mph. it tugs like it wants to take off, but never really gets the chance to kick it to the next gear.

so what happen?

i say it's the carb - carb guy says its the engine

i think it might be the plugs too.

i dunno?

-alex

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70 Plymouth Valiant 4dr

Which ACDelco plugs did you use? Any other engine changes aside from the carb swap and tune-up?

Symptoms such as you describe can be caused by a vacuum leak at e.g. the intake manifold to head junction.

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

I vote for the delco plugs... I have never had any luck with them in any mopar. Others though will scream at my suggestion but so far I haven't been able to beat the Champions in any Mopar I've had, especiallly for their price. For ~$10 its a cheap try. Put the Champs back in there and theres a good chance itll straighten out. Whatever you do, also stay away from the Bosch "Super" plug because theyre also crap.

If you are running a '74 or earlier cylinder head (with spark plug tubes), then use NGK ZFR5N extended-nose spark plugs (if for some strange reason you feel you must use Champions, then use RL13LYC, but the NGK is a better-made plug). If your head is a '63-'74 unit, remove the metal ring washers from the spark plugs before installing them.

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

HI' Is it possible that your catylytic converter is partially plugged? This happened to me once.

He don't describe the car in this post but if I remember its an older one that never had a converter.