Breaking a motor in

[JustinK13]

Has anyone had the experience of breaking a rebuilt or crate engine in? If so how did you do it?...did you put so many miles on it before getting on it? or did you break it in hard? whatever you did please do tell the pro's and con's of what happend, any leaks, any problems at all?

Just curious becuase i just dropped my 390 in and have mixed emotions for both ways.

[DarcSystems]

This is always a tough call. It's a matter of opinion for most people. Some say go easy on it for the first 300 miles, others say beat the bag out of it.

What I tend to do is run it hard for 50 a day, come back, do two oil changes (gets out the metal filings that are bound to come out into the oil) go easy on it for 100 miles, then hammer on it for another 50. When I say hammer on it, I don't mean go to a parking lot for 50 miles and do burnouts, I mean don't be afraid to give it gas, and really wind the motor up.

After about 4 oil changes within 300 miles, you should be fine.

Always worked for me. After the 4th change, cut open the filter, if there are a fair amount of filings in there, you might wanna give it one more.

[wsuwarrior]

Darc would know about as good as anyone about new engines, so I cant really add on to that. Ive only had one brand new engine in my life and i just drove it like i would normally, but changed the oil at 500 and 1000 miles. Then after that every 2000 miles. Ive always just been told to drive it like i normally would, but i know people that just beat on it hard.

[Mainer]

This is always a tough call. It's a matter of opinion for most people. Some say go easy on it for the first 300 miles, others say beat the bag out of it.

What I tend to do is run it hard for 50 a day, come back, do two oil changes (gets out the metal filings that are bound to come out into the oil) go easy on it for 100 miles, then hammer on it for another 50. When I say hammer on it, I don't mean go to a parking lot for 50 miles and do burnouts, I mean don't be afraid to give it gas, and really wind the motor up.

After about 4 oil changes within 300 miles, you should be fine.

Always worked for me. After the 4th change, cut open the filter, if there are a fair amount of filings in there, you might wanna give it one more.

i really dont know much about what the topic is about, but aren't metal filings in the oil alwasy a bad omen no matter what

[Sasquatch4406]

if u wanna break in a motor do this on the first startup. run it at idle for 2 minutes then, adjust the carb or sit in it holding the pedal or wutever so it runs at 2500rpms. run it at 2500rpms for 45 minutes and ull be set. you wont wipe out a cam lobe if u do this

[DarcSystems]

i really dont know much about what the topic is about, but aren't metal filings in the oil alwasy a bad omen no matter what
When breaking in new internals, metal is bound to burn off the sharp edges. Cam lobes, bearings, what have you. That's why you change the oil a few times, so those metal filings don't do any damage. If you leave them in there, then you will be looking at problems, but you "flush" them out with a bunch of oil changes. Rinsing them out of the engine. Kumacho should know what I mean.

[JustinK13]

Thanks everyone, especially Darc i was thinking about doing somethinh along the lines of that already. You helped me decide though. to bad it will be awhile before i get to turn her over due to a new 20 circuit wire harness i just bought :(

[elliott678]

If it has a flat tappet cam, before doing anything else, you must run it for 20min at 2000 RPM to break in the cam. If you have a roller cam you can skip this.

[JustinK13]

Kumacho should know what I mean.

If theres anyway i would like to hear from Kumacho

I dont know if this will help but here are the specs of the rebuild

* 3.780" stroke nodular iron crank
* 6.488" big beam forged rods with Milodon/ARP rod bolts
* 9½ to 1 compression Forged pistons
* Seasoned 2-bolt main block
* Deck head gasket surface on block to ensure a good seal
* New Hydraulic flat tappet cam with .536"Int/.562"Exh valve lift
* Heads have 2.030"Int/1.560"Exh valves
* New Hardened exhaust seats for use with leaded or unleaded fuel
* New 1.440" high performance springs set up to match cam
* New Spiral-type valve guides for better oil retention
* New Perfect Circle rings
* New Double row timing set
* New High volume oil pump with steel drive shaft and bolt on oil pickup tube
* New Brass expansion plugs
* New Edelbrock Performer RPM aluminum intake manifold. This dual plane intake constant cross-sectional area design builds low end and mid-range acceleration while optimized runner path make top-end hp
* For those of you that have the hood clearance we will include a 2" high intake to carb spacer to increase plenum volume. This spacer increases the carb-to-plenum floor distance which atomizes the fuel better and also enhances low-rpm torque and throttle response. This engine takes a square bore carb. It works best with a 750cfm carb (not included)
* All parts are painted separately before assembly for that show quality look

[kms8489]

If it has a flat tappet cam, before doing anything else, you must run it for 20min at 2000 RPM to break in the cam. If you have a roller cam you can skip this.


i thought it was 3000 rpms...2000 is like idling when you first crank it, dont some cars idle at 2000 when you first crank them cause theyre getting warmed up? idk, ive been in lots of cars that do this...or idle higher than normal when theyre first cranked.

[JustinK13]

kms i think you are reffering to the electric choke, which yes does make them idle faster when they are cold. not that it matters or i dont think but i will have a manuel choke

[Kumacho]

The way I have always broken in a new engine:

Never drive at a constant RPM for a long duration and never redline it until 3,000 miles. Avoid lugging the engine down.

I do my first oil change at 100 miles and use the same dual change method Darc does. Only after my first change I start the car and run it around the block a few times. Then I change it again.

The second oil change I do at 300 miles and I don't do a dual change on that one.

I do the next change a 1,000 miles and the final change at 3,000 miles.

Every person you ask, who has been around cars for a long time, will have a different answer for what you are asking. Some will say break it in like you will drive it. Some will say baby it. I tend towards the break it in like you will drive it only don't redline and constantly vary your RPMs.

There are several things you are accomplishing during a break in. One of them was already mentioned by Darc. You are breaking off the small tags of metal on the new parts. This is why you do oil changes so often after a short time period.

The other thing you accomplish is to seat the rings and valves. If you baby the car the rings and valves will not seat as well and the break in will actually take longer.

One other thing you do is season the cylinders and the heads. Heat changes cause them to expand and contract. So you want this to happen at a rate that is similar to the way you are going to drive the car. Metal has memory (of sorts) and you kind of train the metal to expand and contract at a certain rate and to a certain size.

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God I hate typing out a post and having that message pop up!

[elliott678]

i thought it was 3000 rpms...2000 is like idling when you first crank it, dont some cars idle at 2000 when you first crank them cause theyre getting warmed up? idk, ive been in lots of cars that do this...or idle higher than normal when theyre first cranked.

This is what I was told by Comp Cams when I got a new cam for my car. The reason for the increased RPM is because at idle not much oil is getting to the cam lobes. At anything over 1500 RPMs the crank throws oil up to the cam lobes themselves. Without that extra oil it will round off the cam lobes really quickly, after a few mins of running the lifters get the propper crown on them and won't cut into the cam.

[kms8489]

hmm, thanks for posting that. pretty interesting. Makes a lot of sense now.