should i use an engine break in oil, currently have joe gibbs xp4 oil. engine has been dialed in and hot run for about 1 hour.what does anyone think how to break in a new motor 383 has all forged internals and a high flow oil pump.ps what a job getting extra large oil pan under a third gen with keep a ypipe 1992 z28 vert 5speed oh yey its black

 

Initial start up is the most important! Especailly if the cam is a flat tappet one, in which case break in oil would be essentail! If its a roller cam is not that important, But since you've alreadt ran the motor for an hour, just take it easy for the first 500 miles,(try to avoid highway miles) change to regular motor oil (no synthetics yet), then finish the remaining 1000 miles,(highways ok) change oils again and enjoy!
I learned this in engine machining & rebuilding, the miles are to insure the rings get well seated into the bore.

 

Read this and decide for yourself on breaking that engine in. http://www.mototuneusa.com/break_in_secrets.htm Before I knew about that site, that's pretty much how I broke my current 350 in over 7 years ago.