Got an old GTO with a rebuilt street/strip engine and flat tappet solid cam. Builder is recommending a 10w40 oil and says I don't need to worry about zinc since cam is broken in already. I definitely trust him but I'd rather be uber-careful and use something with more zinc in it. Several questions:
1) Anything wrong with putting GM EOS, Comp Cams break-in additive, etc. into synthetic oil?
2) Anybody aware of an off-the-shelf product in a 10-40 or 15-40 with substantial zinc content? Seems as if the closest grade avail in most racing oils is a 20w50. My engine is more of a street setup and I am not sure 20w50 isn't a bit on the heavy side.
Thanks!
1) Anything wrong with putting GM EOS, Comp Cams break-in additive, etc. into synthetic oil?
2) Anybody aware of an off-the-shelf product in a 10-40 or 15-40 with substantial zinc content? Seems as if the closest grade avail in most racing oils is a 20w50. My engine is more of a street setup and I am not sure 20w50 isn't a bit on the heavy side.
Thanks!