Thread: 302 Break-in

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The 302 that I have for the Comet was recently rebuilt. The guy I got the motor from had all the work done but never ran it and I have never gone through the break-in stage of an engine.

I have heard that I need to use 30W oil for 30min. at 3000 rpms.

Is that right???

Thanks for the help
Big Mac

Some say to use non-detergent oils like straight 30w, but I see no reason to do it. I just broke in a 350 Chevy on 10w30. I ran it between 2000 and 2500 rpm for 20-30 minutes. I tried not to lug the engine down by manual shifting it some, and didn't run it under sustained heavy loads like seen on the freeway. I did run it at full throttle for a few seconds at a time after the first few hundred miles. I have about 800 miles on the motor and haven't changed the oil yet, but I used a detergent oil. It will get new oil and filter around 1000 or 1200 miles.

There are alot of theories on how to do this correctly, but this seems to be the best one with modern rings, bearings, etc.

Prelube the engine. I welded a 5/16 socket into a long 1/4 inch extension. Use a strong 1/2 inch drill motor, remove the distributor, and slip the socket over the hex shaped oil pump drive. Spin it in the direction the distributor normally spins, with oil in the crankcase, filled to the normal level.

Run the drill, and you will hear it begin to slow down as it pumps the heavy oil. Do this until you see oil coming out of the rocker arm holes. What you are doing is filling all the bearings, lifters, etc., so you aren't starting a dry engine.

Now reinstall the distributor, and set timing, statically, so the engine will start quickly. Run it up to about 2000-2500 rpms and keep it there for 20-30 minutes. You may have to put a large house fan in front of the radiator to keep it cool, or shut it down and repeat the process a few times.

After this, drain the first batch of oil AND the filter, to get out all machining shavings. You are now ready to drive.

Vary the speeds for the first 10 hours, ie: run at 45mph for awhile, then at 55, then 35,then 45, etc. After 10 hours change oil and filter again, and you are set.

Hope this helps.

The most important part of breakin is the first 5 minutes, the engine has to start right up and run at 2000 or so for that long to prevent galling of the lifters, and possible bearing damage.

When I read your thread subject I first thought your third floor apartment had been burglarized. HEHEHE

Just kiddin'

Break in on a dyno would be the best method, if it's available to you.

Originally posted by pro70z28
When I read your thread subject I first thought your third floor apartment had been burglarized. HEHEHE

That's choice

instead of using a house fan in front of the radiator to ensure cool tempatures... a ford rebuilding manual explains to just use regular water for intial break in.... then stick a garden hose with a decent trickle in the radiator... and open the drain to a little less of a trickle... this technique should keep the engine within proper operating tempature without letting it overheat and give you a bad ring seal

Originally posted by 76GMC1500
Some say to use non-detergent oils like straight 30w, but I see no reason to do it. I just broke in a 350 Chevy on 10w30. I ran it between 2000 and 2500 rpm for 20-30 minutes. I tried not to lug the engine down by manual shifting it some, and didn't run it under sustained heavy loads like seen on the freeway. I did run it at full throttle for a few seconds at a time after the first few hundred miles. I have about 800 miles on the motor and haven't changed the oil yet, but I used a detergent oil. It will get new oil and filter around 1000 or 1200 miles.

Shoulda changed the oil after that initial 20-30 minute run to remove any intial shavings, or at least no later than 100 miles.

If I were you I would change it NOW. Don't wait any longer.

Thanks for the info, I have another question about the rocker.

How can I gap them before starting the car for the first time?

Thanks again,

Big Mac

What type of cam are you running, hydraulic or solid??? Hydraulics are set with a preload, only solid lifters are set with a feeler gauge......

It's a Crane Hydraulic Energizer.