im thinking of getting a zz4 crate engine to start and gradually modify it as needed to support a Procharger 15+ PSI. it has a cast iron block with 4 bolt intermediate mains. what does "intermediate mains" mean? will it be affected over 15 PSI?

 

I would say the three middle main bearing caps.

 

My ZZ4 has 4 bolt caps on the three middle caps not the front or rear where it has two. I dont think you'll have any problems with the ZZ4 block, my friends block cracked in the valley at over 900 horsepower with nitrous injection.

 

SBC engines had three different main journal diameters: 2.30", 2.45", and 2.65". 2.3" mains were used on early 265, 283, 302, and 327 engines. About 1968 saw a change to all 2.45" main journals for all SBC engines, and in 1971 ('72 model year) the 400CID got 2.65" mains from the factory.

My guess is that their note means that you are getting the 2.45", or most common size main journal crankshaft.

I could be way off-base on this, though.

 

was your friends block a zz4?