If you have a flat tappet cam
do not run synthetic oil in it, especially for the initial break in oil.
It is critical that the oil you use has Zinc in it, like diesel oil or racing oils that state on the can that they are illegal for street use.
Oil not containing Zinc can cause a cam lobe to flatten out within minutes of starting your engine and destroy your new cam and lifters.
GM makes a great oil additive for breaking in a flat tappet cam.
If you installed a roller cam run what you have.
