My old '70 was built back when Datsun was using 5 counterweight crankshafts. They're good and solid....up to a point. That point being about 7500 rpms. Then they pull the amoeba trick and become a two-piece crankshaft.

After this problem was discovered, it was corrected by installation of 7 counterweight cranks. Problem solved....go for 8 grand or higher.

Question: What modifications to the block are required to install a 7-CW crank in lieu of the 5-CW OEM crank? Any other parts or pieces that need to be changed?

Wow, I've been building engines since those first came into the states, and I've only seen one, and it wasn't in an engine. I thought they had all been broken or replaced. I remember reading the BRE cars broke their eary cranks, before the later style was available. I believe the later cranks are a direct replacement fit.

Phred

Thanks, Phred.

I'll check with Nissan to see if the 7-CW cranks are available still.

hahaha... amoeba trick....