BLANCK88

I just got a 1971 mach 1 with a 351.

what gas should I use

should I use unleaded or should I add lead substitute?

oxfordbp

Do a search. Doesn't really matter for fuel. It's the oil you need to add more additive. Zddp

BLANCK88

what do you mean oil additive?

oxfordbp

The new oils have less of something called (i think) ZDDP, which our older motors like. Everyone on this forum is saying to use a high ZDDP oil, or get an additive for your regular oil.
I hope that helps. If not do a quick google on it.

andrewmp6

They took the zinc out of motor oils it was killing cats on newer cars,But older cars with a flat tappet cam needs the zinc.I use amsoil z-rod it has the zinc i need for my car and truck.On the lead substitute some people use it some don't i have a 1965 396 in my truck its never had a rebuild it runs just fine on unleaded gas plus look how long ago it has been since they made leaded gas.

oldrock

depending on your setup, you might get away with the cheap unleaded gas but if the engine has been rebuilt for higher compression, you might have to go with super unleaded for best performance. As for the additives, again depending on how the engine was rebuilt, you might have to use the additives in the oil. This is the most popular brand and I've heard nothing but good things about their products. http://www.royalpurple.com/

So how about some pics of the new ride? I got a 70 mustang with a 351c a few months ago so have been doing alot of work on the cleveland motor and just got it rebuilt about two weeks ago.

67 evil eleanor

Zinc is the key to these old engines staying healthy. Like said before, the zink will wreck a catalytic converter so the solution was to remove the zinc. "If" you can find pure gas as I think some stations (Bp) may still sell, use it if you can find it. These engines were never designed to run on alcohol blends or low octane fuels. Lead additives are great for stopping up fuel filters, that's about it. Also remember that the E10 and E-15 will boil at much lower temperatures than the "good old school gasoline" will. I see it every year at car shows when the engine is turned off to regester and when they try to start it back nothing happens. Congrads on your new/old car.