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I just rebuilt the 400 in my 69 GTO. I just cranked it up for the first time today after rebuilding the engine for the past month. I started it and then turned it right off. Talk about a GREAT feeling!! I am curious if anyone has any advice they can give me on breaking in the engine. The engine is bored 30 over and i put in a new Comp Cam. I just want to make sure I do the last step the right way. Any advice will help.

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Next time you fire it up do not shut it off for 30 min. Set the idle above 2000 rpm. this is what breaks in the cam. Most cam manufacturers recommend changing the oil/filter after the first hour or 100 miles. make sure you add some zinc additive or run oil with it.

Then in my opinion drive it like you plan on driving but be reasonable for the first 500 miles. Change the oil again and have at it.
 

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Also, tell us more about the cam and what kind of valve springs you have now. Often with "enhanced" parts and a stronger cam people advise breaking in the cam using the procedure facn8me recommended, but also with the inner valve springs removed. This puts less pressure on the interface between cam and lifters and lets them wear in. Once cam break in has completed (the first 30 minute run), re-install the inner springs and you're good to go.

Bear
 

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agree

agree with above ... keep it at or above 2000 rpm but don't let it just run at steady rpm ..goose it up to to 2700/3000 rpm occasionally... keep an eye on temp and oil pressure ...change oil /filter after initial break in ..use zinc additive again after first oil change just to be sure ..don't lose an engine over a few bucks ....just did mine had water leaking from a lower hose and oil filter just not tight enough ...check connections twice then fire it up
 
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