The widest part of my cam lobe (the fat part at the bottom where the valve is closed and the lifter is farthest down in the bore) measures 1 1/8th" (or 1.125") when I put calipers on it. Does anyone know what this measurement would be on a stock ZZ4 cam? This answer could save me hundreds of dollars...

 

I measured from 1.170" to 1.210" across a number of lobes on a used ZZ3 cam. Has about 20K miles on it. That's more variation than I expected. All readings were larger than your measurement FWIW.

 

Well, 1.21 - 1.125 = .085 max difference. The lowest my lifter goes into the bore is still at the very top edge of the dogbone. So I would say that the lowest the lifter will go into the dogbone with the new cam is .085 from the top edge. The dogbone is .250 tall. 34% of .250 is .085....so the lifter will go down into the lifter about 1/3 of the height of the lifter....

So would you say I don't have to buy new lifters?

 

Sorry!! Let me rephrase that last part...

"so the lifter will go down into the dogbone about 1/3 of the height of the dogbone...."