# Initial startup and break in rebuilt 400



## teamwoody72 (May 23, 2008)

Its coming close to that time to do the initial start up and break in on my 68 gto 400 h.o. motor. I know there are many different ways people go about this. Im looking for opinions. In the past I would take the car out, vary the rpms for and hour at a time but staying under 50 mph for approx. 300 miles. I then change oil and open filter to check for metal. I don't use any break in oil. Looking for opinions.


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## Rukee (Feb 8, 2007)

Be sure to read the CAM break in procedure as most have you rev the motor to about 2500rpm's for a number of minutes. Be sure to check your timing. Sometimes I will pull the coil wire and crank till I have oil pressure before first fire up. Keep the radiator cap off until you verify that the coolant is in fact flowing when it gets to temp. After you're on the road you're going to want to do some runs. When you rev the engine hard (but I wouldn't go over 4500-5000rpms) you're seating the rings. Then after accelerating hard you want to back off the throttle and let the engine slow the car, doing that will suck oil up to the rings. I will do that 5-10 times (my machine shop gave me that tip). Then from a stop I'll just floor it and let it run through the gears without over rev'ing to see what she's got. I do this for two reasons, first I know the owner is going to do this to see what he just bought, and two if it blows apart I want it to blow apart on me and not the paying customer! By the way, I've never had one blow apart.


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## geeteeohguy (Feb 2, 2008)

What Rukee said, and I'll add: the cam break in is usually 20-30 minutes at 2500 rpm. Good idea to have a box fan blowing at the front of the car. Also a fire extinguisher on hand is a good idea. I always dump the oil after the cam break in to get the goopy cam lube and initial debris out of the engine. Cheap insurance. Then, new oil and filter for the engine break in, which I always change after 500 miles. You don't want to run it at constant speed or at cruise much during break in. A lot of varied speed driving.


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## leeklm (Mar 11, 2012)

And be sure to run a hi zinc oil like brad penn, or an additive like gm eos lube. I recently had two lobes go bad on a new cam that I was running 15w40 oil and an additive. Not sure what went wrong or when things started to go bad. 

I then used straight 30w and the gm additive when breaking in the replacement cam. After break in procedure as noted above, I have been using regular 10w40 with lucas zinc additive, and so far, so good...

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## teamwoody72 (May 23, 2008)

thanks guys.


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