Rebuild 302 Break In

[PNW]

Previous Owner said he had 302 rebuilt. Don’t know much more than that. Bronco has been sitting for 10 years. Started and ran for the first time this week. Anything I should know about conditioning/breaking in the motor?

 

[73azbronco]

It was never run before?

Roller rockers? Lifters solid or hydraulic?

You will have oil leaks, probably air leaks, and water leaks.

All the fluids new?

 

[PNW]

It was never run before?

Roller rockers? Lifters solid or hydraulic?

You will have oil leaks, probably air leaks, and water leaks.

All the fluids new?

It was my understanding that it was run before.

Don’t know rockers, solid rockers or hydraulic...still learning about engines.

All new fluids!

 

[B RON CO]

Hi, the old school break in was to get it started and run it for 20 minutes, while keeping the RPMs @ 2000. The high RPMs assures the oil is splashing around the cam and lifters. After it initial run in you change the oil and again at 500 miles. Good luck

 

[PNW]

Hi, the old school break in was to get it started and run it for 20 minutes, while keeping the RPMs @ 2000. The high RPMs assures the oil is splashing around the cam and lifters. After it initial run in you change the oil and again at 500 miles. Good luck

Thanks! Will try it.

 

[Jfryjfry]

Follow that with several full throttle runs in 2nd up to 5k or so and then lift off gas and let it coast back down to 5mp or so and repeat.

The initial 20 minute run is to break in the cam and this is to seat the rings.

 

[EODMike]

Previous Owner said he had 302 rebuilt. Don’t know much more than that. Bronco has been sitting for 10 years. Started and ran for the first time this week. Anything I should know about conditioning/breaking in the motor?

Make sure you use an oil that has Zinc in it or use a Zinc additive such as from Lucas Oil. I ran an oil (5w30?) in my newly rebuilt 302 in October for about 5 minutes and destroyed the lifters, cam and one or two pistons. Had to rebuild the engine again from the damage. Lesson learned about using thicker oil during break in.

 

[Broncobowsher]

Zinc additive for the flat tappet cam. Unsure if it was broken in before or what cam is in it. Just run a bottle of zinc for now. Won't hurt anything, good chance at saving stuff.

FYI the zinc was removed from normal oil used in modern cars for emissions reasons. Won't hurt an old engine by running it. Once broken in you don't need to add it anymore.

As for the advice on making 5k passes on a fresh engine, 4k is a lot better choice. You may not have the valve springs to hit 5k if it was a stock build.

 

[Rustytruck]

Make sure you use a thermostat in it and run it like you plan to use it. don't baby it and don't run it for hundreds of miles at a set speed like tooling down the highways for 4 hours. Then change the oil and replace the oil filter, cut open the filter and check for failing exposed metal. Then go enjoy your Bronco.