I'm looking at purchasing a 1971 351-2v Mustang. My question is....did they still use leaded fuel back then or was the switch to unleaded in place at that time? If it was still leaded, what additive can be used with today's unleaded fuel for the 351-2V. Thanks in advance for your help.

 

I think they used leaded back then. If the heads are OEM stock ( and if they did infact use leaded ) you will need to change the valve guides. Then you can run unleaded.

 

Yes we had leaded fuel back then.Running unleaded won't hurt the engine unless you regularly run it hard.Highway driving is OK.If you want to take the trouble you can look to see if there is hardened valve seats installed in the head,this will rquire removal of the head.Hardened valve seats can be installed by any competent automotive machine shop.Valve guides are not effected by unleaded gas.
If you are planning to race the car frequently you might want to think about getting a better set of heads anyway.

 

LOL I knew it was something in that vicinity.. thank for the correction.