I see you know what you are talking about on the zz4 so here is my question what is the diffrents between the zz3 and the zz4? I have my eye on a 87 zz3 with all the block work done 30 over the steel crank 10\10 zz3 cam. ballanced rods and roller lifters $550. No piston as of yet. Do you know if the cams on the zz4 and 3 are the same? I see there is like 10 hp diffrents between the two motors.

Thanks in advance

 

My info is a combination of a bud with a ZZ3, and what I've read. So, it's not exactly gospel.

But...

Here's the Service Parts List, that covers all the ZZ engines. http://www.gmgoodwrench.com/crate_en...all/zz4pl.html

From that, you can see: Misc. bolts & fastners different (went Torx on ZZ4). The ZZ3 and ZZ4 cam is the same thing. ZZ4 heads (same casting as ZZ3) use LT4 valve springs and seals (I thought the retainers were different, too). ZZ4 has PM rods (some later ZZ3's apparently did as well). Pistons and rings different (I think the ZZ4 compression is slightly higher than ZZ3, but I'm not completely sure). ZZ3 had steel crank, ZZ4 nodular iron. Oil pumps are different (not sure what about them is different).

Hope that helps.