Any old-school tricks for "loosening" a tight V-8?
 

My rebuilt 428 is pretty tight. I can turn it from the front bolt on crank,but it takes a little bit of muscle. Therefore, seems like a lot of stress for the starter. We did do the initial 20 minute break-in run. Still tough on start-up! Any tricks other than just to keep on running it?

Nope. It just needs to run in and it will loosen up. Just sitting and idling probably won't do much for it, either. It needs to see some loaded mileage. In the near term, as long as it starts, runs, and carries good oil pressure, you've got no worries.

Hastings (as in piston rings) has an excellent write-up on breaking in a fresh rebuilt engine:

Breakin Procedure

Any old-school tricks for "loosening" a tight V-8?

A fancy dinner and a diamond encrusted bracelet maybe......

Don't forget champagne, candle light and Barry White!

Yeah, especially Barry White....LOL Geez you guys crack me up. John

roofies on the champange(gasoline)

He said he want to loosen up the engine....he doesn't want it to forget that he broke it in!!!

Run it and make sure that your starter has good connections...especially the ground...sometimes paint on a fresh rebuild will insulate the starter a little & result in slow cranking. Also check the connection of the battery ground to the block.

Dan