[dingjohnny]

I just rebuilt the engine on my 5.0. I put in a f303 cam and while i was at it I put in new main and rod bearings. Is there a break-in period? How soon until I change the oil?(I used plenty of assembly lube) And how soon till I can race the engine?

[MadMatt]

What I do is about a 20 min fast idle after first startup (1500-2200 RPM) kind of bringing it up and down. Then I put in new oil and a new filter right afterward. This gets rid of any contaminants that may have been in there from the build and any metal shavings from the initial break in. After that I take it for a nice easy 100 mile drive or so in stop and go type city driving, not a highway cruise and then change the oil and filter again. After that she should be good to do whatever you want to it. Just don't use synthetic oil till you have around 3000 miles on the motor.

[cnumartyr]

Originally Posted by MadMatt

What I do is about a 20 min fast idle after first startup (1500-2200 RPM) kind of bringing it up and down. Then I put in new oil and a new filter right afterward. This gets rid of any contaminants that may have been in there from the build and any metal shavings from the initial break in. After that I take it for a nice easy 100 mile drive or so in stop and go type city driving, not a highway cruise and then change the oil and filter again. After that she should be good to do whatever you want to it. Just don't use synthetic oil till you have around 3000 miles on the motor.

I agree with that all except one thing. I'd take it easy on it the first 3000 miles to let the rings fully seat. After that get into it. I've always heard (rumors, perhaps) that it's best to let the engine have an easy first 3000 miles and to change the filter twice during that time (1500 Mile Intervals).