Could using unleaded fuel cause my engine to run rough and chug? I don't know if the previous owners of the car used a lead additive. Should I try the additive?

 

I've never seen it to make a difference. I have a 66 289HP that runs just fine on straight pump gas.

 

you should try to know it.

 

There were several reasons for adding lead to gasoline. First lead improved gasoline burning. Second it helped eliminate or reduced the knocking caused by premature ignition in high-performance large engines and in smaller high-compression engines. Lead also provided lubrication--which is why alot of people add hardened valve seats when they have heads redone.

I've never heard of lack of using the additive cause a chug however?? Sounds more like fuel delivery issue if its a new problem.

I ran my 69 Camaro for years with adding anything and never had any issues.

 

In a word...no. In another word...it sounds like you're running lean. Can you post what problems you're running into? I think you've heard things that are influencing your.....guesses?

 

I think you just need to adjust your carb or maybe rebuild it they do get dirty with age.What brand gas do you run ?

 

I just bought the car about a month ago and the previous owner didn't drive it that much. I filled her up with Premium Gas from Mobil. I added sea foam and some carb cleaner that you add to the gas. I am wondering if I added too much to the gas.

 

Probably just needs a tune. Fuel today is radically different than fuel from the 60's. The lead won't really matter except as a detonation resistor(which isn't really an issue unless you're running high compression). But modern fuels burn more rapidly, are oxygenated(meaning they WILL run leaner) and have different specific gravities(which will alter air/fuel ratios).

 

Seafoam works to be sure--guess there is a possibility you loosened up some crud in your fuel system that is now gummin up the works. Again its a fuel delivery issue not the lack of lead.

 

+1 if the car has been sitting around unleaded fuel goes off and attracts moisture over time. add a little tank rust and bingo. Do you run a fuel filter in line?

I agree with getting the thing tuned - it could be carb, plugs, timing, sticky points (if still running points) or fuel.