What oil would you use on a new rebiuilt motor and how long would you run it without a change? 302 V8.
Use regular dinosaur based motor oil for initial start-up and break in. Figure 10W-30 should be fine. Once your initial start up is complete change the oil and filter using regular oil again. Same weight should be ok. Do this for 500-1000 miles until you feel the engine is fully broken in (rings are seated, mileage is consistent, etc). Then switch to a synthetic of similar weight. Some people use 5W-20 or 5W-30. I like 10W30 Royal Purple myself.
Use a diesel spec oil or a new flat tappet motor. One with lots of zinc is what you want. Run it 30 minutes till the cam is broken in, change oil and filter. Run it another 500 miles, change again. Then it's good to go 6 months or so between changes.
I agree, but want to stress the need for the diesel spec oil like baddad said, or at maybe just add the cam breakin additive for the first 3 oil changes or so, but only if flat tappet. There has been a rash of failed flat tappet cams and lifters due to improper break-in lube and/or procedure. Apparently this is a relatively new problem as they have reduced some of the minerals in the new oils to assist cat converters or something...maybe in the last 5 years or so...anyone know the exact reasons and details? If roller cam, you should be able to just follow the other shadow's guidelines.
i start up with the ..."cheapest oil"... i can buy... i do no ...cam break in... after i get the car up and ready for a road test...i change the oil and filter...this is more to remove any junk that is in the motor from the build. then i put in what i am going to run...next to the cheapest... run that about 500 miles and change the oil and filter again. next change ...when i think about it. has worked for me for 40+ yrs. in all my street motors 170 6cyl-472V8. ...ILMAOD...
Flat tappet cams are made from ductile cast iron, which is relatively soft, so it needs all the protection it can get during initial start. Yes, oil formulation has changed since most engines are rollers anymore. The diesel oil is a very good recomendation. Most people will recommend revving a brand new flat tappet to 2500-3000 RPM on initial start, because this insures full oil pressure and flow. Best thing you can do is to NOT baby the engine. Run the crap out of it. Best thing you can do for a brand new short block. Well, provided that it was put together right and it's not leaking anything.
The flat tappet cam lobes, while made of "soft" iron are very hard due to the case hardening process. This makes the lobe surface (to a depth of about .003") very hard. I always vary my rpm (above 2000) for the first 20 to 30 min. of run time.
Since when are cams case hardened??? Also, who only carburizes to .003? Did you mean .030? I can see the aftermarket maybe case hardening, but the OEM would not have been able to justify the cost. Case hardening ductile cast iron isn't very smart to begin with. You might as well just use a high carbon cast iron and skip the extra step. Roller cams are through hardened due to the higher bearing stress on the lobe, and that is a completely different animal than case hardening. The only kind of surface heat treatment I've ever seen on ANY OEM part is nitriding crank shafts in diesel engines. Even then, you only surface treat forged or wrought alloys, not castings.
