Freshly rebuilt motor, what to do/not do

[BigClay]

I have never had a motor rebuilt before, so what do I need to do or not do to make sure it is broken in properly. How many miles for break in? When do you change the oil? No towing? No long trips? Limit short trips?

 

[McCracken]

first thing I do is mash on it and see how many rpms I can get out of it.

just kidding, don't do that.

 

[criket]

There are several different methods
For me,
Be sure that you properly seat the valves at first start up (20 minutes at 2000-2500 rpms varying).
Other than that run break in oil for a while, I think 100 miles or so miles? Be gentle and then do an oil change. You should be able to use regular/synthetic oil.
Then I'd change oil again at 500 and then 1000 miles. After that, you shold be able to do your normal routine oil change procedure.

Someone correct me if I'm wrong.

 

[6BangBronk]

1'st is to prime the motor by spinning the dizzy / oil pump and monitor oil pressure and to wash out grime to the pan. First start, carb should be jacked to about 2500 rpm's and let run for good 10+ minutes. Let everything smoke off and run longer if lifters are still ticking. And make SURE it cranks immediately. Do NOT drown with priming. If it don't start after a few tries, something's wrong. If you over drown a carb, it goes where, straight into the pan where it breaks the oil viscosity down and all that rebuild grit gets clogged on the bearings and motor locks up and you've just wasted a couple grand. Monitor the temp so it don't overheat and make sure oil pressure is steady. Oil pressure will be much higher cold than after it warms but make sure it don't exceep 90-100 pounds for that's a typical oil filter limit. Change oil BEFORE 500 miles cause all the shavings should be down way before then.
It's ironic but every manual I've read explains how you NEED to break it in at different RPM's to seat everything properly. They say to irradically start cold at high rpm's and then another day low and drive faster one day and slower the next. But don't go hog wild. Wouldn't tow or go over say 5,000 rpm's until after first oil change to keep all the bad at the bottom of the pan.

Another tip I've found extremely useful is to report the compression for all cylinders just after the initial cranking to fall back on later for diagnosing anything to come.

And lastly, PLEASE stay away from a mechanical fan when cranking a new motor. I just experienced my first water pump shaft shear and fan tried to eat my radiator. Told work mate about it and he said his Dad had a huge scar on his chin from a fan flying off from leaning over and revving a new rebuilt motor. Me and my brother-in-law were all over mine revving and then my second cranking 30 minutes later from inside the cab and bro-in-law standing back, all hell broke loose... Just got her back up to where I was at last night replacing rad / water pump and all and wiring up my new elecric fan.

 

[transman731]

i don't recommend using synthetic oil for break in, after the first oil change it's fine but rings and cam tend to seat better using conventional oil.

 

[UTfball68]

I always use the Shell Rotella 15w-40 dino line of oil for break-in, plus zinc. I run for 20 minutes at 2500 rpm. Change oil, zinc and filter (same as break in type). Run the next 1000 miles driving like a grandma. Change oil and filter (same as break in, no zinc). Drive regularly until 3000 miles, change oil and filter again...use whatever you want and enjoy the new engine the way it should be enjoyed.

 

[catfishblues]

A lot depends on the motor. What is it? I personally believe most break-in procedures were designed for vehicles with flat-tappet cams, where the lobes had to wear into the lifters, otherwise there would be problems. Low-zinc oils have made this harder, but additives are available. I think most modern engine's "recommended break-in procedures" are more there to make the customer feel better about their purchase. (I also think oil change schedules are vastly underestimated too, though.) Modern materials and manufacturing techniques have made motors tighter and better suited to a "get in and drive" style of break-in that most cars see today. Think about it, do you take it easy when you test-drive a new car? Do you think the transporter that may have driven it from a dealership a couple of counties away babied that Corvette? Have you ever bought a car with 0 miles on it? No. If any "damage" was going to be done, it probably would have already happened.

As for your new motor, talk to the builder and see what he or she recommends, and do that. Otherwise, let it warm up good before you drive it. The rings will probably seat in the first 15 minutes or so, and the rest of it's pretty much going to do what it's going to do. Take it easy for the first 100 or so, change the oil at 500 or so, and you'll probably see the same results as if you followed a 1200 mile break-in procedure. Of course, this is assuming the rebuild was on a modern engine.

One more thing to check is if your builder's warranty is invalidated if you don't follow their break-in procedure. If so, then stick to it like it's law.

*Legal disclaimer: My opinions are mine based on my experiences and limited research. Listen to me at your own risk. Your mileage may vary.

 

[1983Bronco]

Have keith dyno it to break in the cam, run oil with zinc additive for 1000 miles, change it, then run the piss out of it

 

[Kamel]

If you are using moly rings, an old black badass motor builder told me: Once everything is back together, crank it without any water in the radiator, and the cap off. Prime oil pump, then crank. Let idle till you see steam coming from radiator. Cut off. Let cool completely. Repeat. Cool completely. Change oil, fill with water/antifreeze and drive. Drive, drive, drive. Drive it like you plan to forever. But most importantly drive it out on the open road. Without starts and stops. For like an hour. Once back home, change oil. I can tell you that you can tell when the rings seat if done this way. Also, I have done several this way.

 

[NC-V]

First and foremost: If there is a warranty or you know the builder then follow their recommendations for warranty purposes.

Now you will obviously get many different responses about this, this is just from my experience (building anything from 800 hp n/a LS motors to 1st gen small blocks and diesels) and discussions with some of the best builders out there. After most rebuilds, there are generally at most 3 or 4 reasons for a "break in" period.

If it has a flat tappet cam, then the cam and lifters need to "break in" together. This is done after priming oil system (as stated already, use a dino oil with zinc additives or an actual break in oil). Fire up engine, set timing and run for ~20 min between 2000 and 2500 rpms. If running a roller cam then no cam break in is necessary.

Next is Seating the rings. This is very important for a good running, powerful engine. The rings need to seat to the cylinder walls or you could have low compression, excessive blow by, oil consumtion etc. There is somewhat of a window for this to happen. As the engine heat cycles over and over the walls of the cylinder will harden and if the rings haven't seated properly by this time your stuck with it. Now if your carb is dumping too much fuel then cyl walls will get washed down and the rings will not seat properly. The key to seating rings is cylinder pressure, you need to push the rings out against the cylinder wall for them to seat, you get cylinder pressure by loading the engine.

Something else that may need to be broken in is the valve springs. This depends on the spring and manufacturer, but some springs need to be heat cycled to finish treating them. This is done per manufacturer specs but usually just requires warming up the engine and letting it cool completely a couple times prior to beating on them.

The final reason for break in is to wash any leftover crap out of the engine and into the pan.

My typical break in procedure: Double check everything, fill with break in oil, fire motor and get timing close (if distributor, if injected I'll make a start up tune), if it is a flat tappet cam I'll run it through the procedure above. If not, I'll just warm the motor up and check for leaks then let cool. Repeat heat cycle at least one more time. Change oil and check filter for anything alarming, sticking with break in oil. At this point (assuming no engine dyno, and engine in vehicle) I would tune the engine's idle and part throttle fueling and timing, carb or injection. After that, strap it on the dyno and start making pulls (No better way to get cyl pressure than full throttle pulls on a dyno! ) . When done tuning, drive it like you stole it. Change oil at 500 miles and inspect, refill with your favorite oil and be on your way.

Obviously there are many different types of engines and components out there which is why the builder should always be consulted. This is just my .02

-Kyle