Does anyone know if the genIV carbed 390h.p. 502 has a forged crank from the factory or not? All my searching said yes, but I want to be 100% sure. Thanks in advance.

ob,
Someone is probably going to proove me worng on this, but I didn't think there was such a thing as a cast 502 crank so I would have to say that yours is definitely forged ?

Bill Koustenis
Advanced Automotive Machine
Waldorf Md

Your 390/502 has a forged crank.


There's no such thing as a cast 502 crank (as supplied in a motor sourced from GM). All cranks that came from GM in a 502 are forged. All pistons that came from GM in a 502 are forged (but there are several variations). All rods that came from GM in a 502 are forged and have 7/16 bolts. All heads that came from GM on a marine 502 are rectangular port (some crate motors had alternate heads).

There's no such think as a Gen IV 502. The 396/402/427/454/502 Std Deck GM Big Block is a MkIV thru around 1990, when the Gen5 was released.

MC

MC, All good information. I think he was calling the MkIV block the Gen IV. To further your post, in 1998 the Gen 6 block was brought into production by GM. My Merc 7.4L
330P motor was a Gen 6 block. Along with:
http://www.crateenginedepot.com/ZZ-5...P9419C604.aspx

Thanks for the response guys. All the searching I did, I couldnt find a cast crank either. I just wanted to double check before I purchased this engine. Again, thanks for the help.

Rotax454,


You are correct. I was calling the mkIV the gen IV by mistake.