I have flat tappet cams and after breaking them in I bought some mobil 1 full synthetic oil. Do I need to add a zinc additive to this?

Not with mobil 1. Some of the grades have higher zinc levels. Check their website they have a info sheet on what ppm levels and grades,

Wannabe

I know I'm going to get flamed by others for this post but don't waste your money on full synthetic oil for which your motor won't like as much as 20w50 Kendall GT-1 or even Brad Penn.
Kendall still has about highest amount of Zinc and Phosphous as a street driven engine with catalyst can handle.
As for the Brad Penn, it's still the good old boy oil with tons of what your engine likes
Both oils can be ordered on Amazon and even offer free basic shipping.

Not going to flame you about your statement. I have been running Mobile 1 for years. A buddy has the same setup as I do and he runs Kendall GT-1. What about the motor, likes the Kendall any bettter than the Mobile 1? Neither of us have had any oil related problems, so just wondering what you thought is. Oh yea, his Kendall cost as much as the mobile 1.

$49.20 a case delivered....
I will get back to ya on the GT-1 data sheet.

http://www.phillips66lubricants.com/...w%20778549.pdf

If you are worried about zinc, go to the Brad Penn it has the zinc you want and is a semi-synthetic. I get for half the cost of Mobil one. I have used both with no problems.

You can see why Brad Penn is a cut above Kendall...
http://www.amref.com/CMSFiles/File/b...HP_Oils_PB.pdf

I have run Mobil 1 15-50(original formula with gray cap) in my last 2 boats for a total of about 650hrs.
The 5252SC in my Pantera had a flat tappet cam that I later upgraded to a roller after about 150hrs. The flat tappet cam was still like new with 350hrs on it.

Mobil 1 has changed over the years we no longer use it. For flat tappet's the zinc levels are low as required by EPA/DOT.
Steve