hey I was just trying to look into what I need in terms of break in oil in a 4.0 I just finished rebuilding my motor got it all in the truck and hooked up except for the distributor to preoil it.
if any of yall could give me some insight on what I need to do that would be great thanks.

 

6 Quarts of 10W30 Break-in oil or 10W30 Conventional oil with a good Zinc Additive. Start her up, check for oil pressure & leaks. If it's all good then immediately pull RPM up to 2000. Vary the RPM between 2000-2500 for 20 minutes. Change oil & filter, use the same oil type again. Then get her on the highway and seat the rings. From a 40 MPH roll, floor it up to 80 MPH, then coast back down to 40 MPH and floor it again. After 10-15 pulls, you should be good to go for 500 miles. Change oil again after that 500 miles. You'll want to use a Zinc additive for the first 5K Mi.

 

OK awesome thanks for the help exactly what I will be doing then. Is there any preference between zinc additive and break in oil was not very sure of the difference. And want to do this right. Thanks

 

Break-In Oil is just detergent free Conventional Oil with a high level of anti-wear additives, like ZDDP. So you either have the choice of your favorite Conventional motor oil combined with an additive, or just pouring in straight break-in oil. Either way you achieve the proper oil. Just don't use synthetic oil at all for the first 5K mi. Synthetic oil has a far stronger film strength than conventional oil and way more detergents. It sounds strange, but you need some metal on metal friction for an old pushrod motor to break in properly. Especially the Flat Tappet Cam and Cast Iron Rings.

https://www.summitracing.com/parts/cca-1590-12

https://www.summitracing.com/parts/cca-159

 

What I have used successfully;
Royal Purple Break-in oil

ETA: I got it at my local NAPA