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new bottom end break in questions

Guest Anonymous

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Guest Anonymous

i'm finally ready to start the break in process on my new bottom end and wanted to get any advice on how i should drive the first 50 miles.

i've been told that i need to vary the rpms and not go over 3500.

i just started her up for the second time and she sounds great. i'm lettin the motor cool for twenty minutes before i go out and drive.

any suggestions or words of wisdom?

many thanks to all of you who helped me with information and encouragement. knock on wood that it lasts.


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Guest Anonymous


URL: http://www.zeebuck.com/02bc/

Avoid lugging the motor at low rpm and getting close to redline, but don't baby the motor. You need high cylinder pressures to make the rings seat against the cylinder walls - the spring tension is *not* what pushes the rings against the walls - it is the pressure. The first 20 miles are the most critical, after a bit of running the sharp edges of the cylinder wall hone marks will have worn down and they will no longer work to machine the rings (that's what gives a perfect seal).

More info here:


good luck,


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Guest Anonymous


Date: Mon, 18 Dec 2000 21:33:42 -0800 (PST)

From: John Bolhuis

Subject: [uuc] New engine break in recommendations (long)


Chris and I were mailing back and forth. Does anyone have a good

link or a procedure they feel is good for new engines? I kind of have

my foot in my mouth. I don't want to steer him the wrong path...


Looking into the wayback files, I pulled this post from the Saturn

list from way back in late 1994. It may be the only break-in post

I've seen that has reasons for its actions. Whether or not you agree

with them, or whether or not BMW engines deserve the same treament,

well maybe that will generate some more gearhead-related discussion

here, which we could use. As for Ben Sloss, I left his name & address

attached, but I have no idea if he's still at that address.

Remember, if you reply to this message, EDIT & TRIM! (and run

through the spell checker for good measure)

Ben's guide to 4-stroke engine break-in:

The Practice. For the first 100 miles, only take short trips of <15

minutes. Do not rev above about 3500 rpm. Use full throttle in short

(2-3 second) bursts at low rpms (say 2500) - 5th gear on the freeway

is ideal for this. Do not do more than one full-throttle burst in the

same 2-minute period. Avoid driving for more than 2-3 minutes at the

same rpm - if you are on the freeway, vary your speed and alternate

between 5th and 4th gears.

>From 100-500 miles, increase the peak RPM you reach by 200 rpm each

time you drive the car (but don't go higher than redline). Do not rev

to your new peak under heavy throttle; instead, let the engine drift

up to the rpm under light load. For instance, pulling away from a

stoplight, leave the engine in first and accelerate lightly until you

reach the desired RPM, then shift. Continue the full-throttle-burst

procedure. Do not rev the engine high under full throttle, and do not

do either the peak-revving or the full-throttle procedure more often

than once a minute. Avoid driving for more than 5 minutes at any one

rpm - again, alternating between two adjacent gears and varying your

speed will work.

You will notice that each time you reach a new peak rpm, the engine

will be quite loud at that rpm, but after a few runs up it will quiet

down. This is a sign that the break-in is proceeding well. You will

want to have revved the engine to 6500(5500) rpm a few times by the

time you reach 500 miles. At that point I recommend you change the

oil, as most of the metal wear and contaminants from break-in are

released in the first 500 miles.

>From 500-3000 miles (the extended break-in) you can operate your

engine fairly normally. Most of the work is done. You should still

run the engine at higher RPMs on a regular basis (assuming you don't

in the normal course of driving ;-) ) and you should avoid prolonged

high-speed/high-stress operation, like racing or cruising at 110 mph.

I personally change the oil after 1500 miles since it will be dirtier

at that point that it would be after 3000 miles of post-break-in

operation, but it isn't critical. Be sure to change it at 3000 miles,

however. Although there is some difference of opinion on what KIND of

oil to use during break-in, the general consensus is to use normal

(non-synthetic) oil of the recommended weight (5- or 10-30).

>From 3000 miles onward, your engine is considered broken in. It will

probably continue to "loosen up" a bit over the next 3000-6000 miles,

so look for a small increase in gas mileage. Other than that, your

engine is now be ready for a long and productive life. Enjoy!

***** BEGIN TECHNICAL SECTION ***** [some of this is what I remember

from articles I have read and discussions. I cannot vouch for the

complete accuracy of what follows, but I believe it to be essentially

correct. If you *must* flame me, please do so in private unless you

think I've made a mistake which everyone need to know about to avoid

doing something unpleasant to their car]

The Theory. The primary goals of engine break-in are: 1) achieving a

good seal between the piston rings and cylinder walls, and 2) allowing

the engine to operate correctly throughout its RPM range. The major

enemy during the break-in period is localized heat buildup, mainly in

bearing surfaces (most notably the crankshaft bearings).

Initial state: When the engine is machined at the factory, many

wearing surfaces (places where parts rub against each other - cylinder

walls, bearings, etc) are purposely machined more roughly than they

could be. The reason for this is that it allows the engine to

complete the machining/polishing as it operates, thus allowing for the

individual variations inherent in any manufacturing process. This

wearing process, when complete, produces parts which will fit together

with very tight tolerances. However, the process also involves a

great deal of friction, which in turn means a great deal of heat. As

metal parts heat, they expand slightly. If the expansion goes beyond

a certain point, the parts will tend to bind with and/or score each

other. This must be avoided.

[To put this in plain english, the parts which rub against each other

are left a bit rough, and as the engine runs the parts will scrape

against each other until they wear down a bit and have a proper fit.

While they're still in the process of scraping, they can get very hot;

if they get too hot, they will damage each other in a permanent way.]

Since this sort of heat buildup is very localized, it will not show up

on the engine temperature gauge. Therefore, it is important to

operate the engine in such a way that the heat buildup will not reach

a dangerous level. More on this later.

Stress and Variation: Although the engine parts are metal and, as a

rule, quite rigid, they are still subject to slight deformation when

stress is applied. The largest stress in a piston engine is that

produced by reciprocating parts. The forces involved increase with

the square of the RPM. Any deformation will necessarily involve a

change in some tolerances inside the engine. Thus, in order for the

engine to operate properly over a range of RPMs, it is important that

it be exercised over this range during the break-in process so that

the wearing parts will experience the range of tolerances they will be

subjected to during normal (post-break-in) operation. Further, for

the wearing surfaces of reciprocating parts (most notably the piston

ring/ cylinder wall interface) operation at a single RPM for an

extended period of time will cause the machining process to progress

significantly further within the confines of the part's range of

travel without progressing at the point just outside that range, thus

building up a small ridge of metal just above the point of maximum


[in order for your engine to run well from 1000 to redline, you need

to operate it at all those rpms while it is breaking in. If you

don't, the parts won't be used to working at the rpms you neglected,

and they won't work as well at those speeds]

Piston Ring Sealing: The seal between the piston ring and the cylinder

wall is crucial to getting good economy and performance from the

engine. A bad seal will allow more blow-by, reducing the amount of

power the engine can produce with each power stroke and thus reducing

both its horsepower and fuel economy, as well as allowing combustion

gasses to get into the crankcase and contaminate the oil AND allowing

oil to get into the combustion chamber and be burned, producing the

characteristic blue-smoke-from-the-tailpipe syndrome (note that oil

can also get into the combustion chamber via the valve stem guides,

but that's not something we can do much about during break-in). The

key to getting a good piston ring seal is high combustion chamber

pressures. Embarrassingly, I don't know why (can someone fill me

in?). High combustion chamber pressure is produced under hard

acceleration; also, the lower the RPM the longer that pressure is

maintained during each power stroke. SO - to get a good piston ring

seal, hard acceleration at low RPMs will give the best results.

Since hard acceleration also produces more heat and more stress

(leading to friction and still MORE heat), it should only be used in

brief bursts, followed by a couple of minutes of "normal" low-stress

operation to allow the heated parts to cool down.

Localized Heat Buildup:

As previously mentioned, wearing parts will produce inordinate

amounts of heat as they polish each other. This produces local points

of intense heat inside the engine, with temperatures far higher than

the engine as a whole (which shows up on the temperature gauge) or

even of the surrounding parts. The most susceptable points in an

engine for this kind of heat buildup are the crankshaft bearings,

which must withstand enormous stress and pressure. If the bearings

are allowed to get too hot, they will expand to the point of scoring

each other or (*gulp*) binding, producing a spun bearing. During the

initial stages of engine break-in, there is no satisfactory way of

keeping these bearings cool during even mild engine operation except

to turn the engine off after every 10-15 minutes of operation and

allow the bearings to cool down.

The theory I have outlined about should now be sufficient to explain

the "practice" section of the break-in instructions. For the first

100 miles, keep the rpms low and the trips short to minimize the

stresses and heat buildup in the bearings, and use short full-throttle

bursts to seal the piston rings. From 100-500 miles, gradually

increase the RPMs to allow the wearing surfaces to correctly mate, and

continue using full-throttle bursts to ensure ring sealing. Use

cooling periods (the 1-minute rule) to minimize the heat buildup

produced by the high RPM operation and the full throttle bursts. At

500 miles, change the oil to flush out all the metal particles

produced by the wearing process.

I hope everyone finds this information useful. If you have comments

which are of general interest, please post them - if you just want to

flame me for making a mistake, please email me so that we don't make

everyone endure a huge firestorm. I should also note that I practice

what I preach - at 7000 miles my CBR is more powerful than anyone

else's I have ridden and its oil is clean after 2000 miles of

operation, while my Saturn SL2 at 10,000 miles is getting 29 mpg

overall and consumes no oil at all.

Ben Sloss Database Kernel Hacker Email: ben@versant.com

Quote: 'It's all fun and games until someone gets paid.'

Transportation: '83 CB650SC (straight roads) '93 CBR 900RR (twisty roads)

'93 Saturn SL-2 (wet roads) '91 XR 250L (no roads)

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Guest Anonymous

All good suggestions. I just skimmed but did they mention oil? Don't use detergent. Use 30 wt non detergent for 1st 500 miles then change oil and filter to your choice of detergent oils. Non detergent is available at NAPA. Where did I get this? Years and years of experience with many different engine rebuilds, including auto, small engine, motorcycles, airplanes, etc.

Reason: Non-detergent allows microscopic metal filings to be suspended in the oil and helps with wearing in the engine.

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Guest Anonymous

leaks from the front timing chain cover? I'm on my second attempt to seal it up. I'm using the Permatex RTV True Blue 77b on the top of the bottom timing chain cover, on top of the head gasket area that extends for the timing chain, the sides of the top front timing chain cover and where the head and top timing chain cover meet.

I'm really keeping my fingers crossed that it's sealed.

I can't tell you how bummed I was this afternoon when I was all ready to start my first break in session only to discover that my top front timing chain cover was leaking like crazy.

With some luck and a lot of rtv MAYBE I'll be able to actually drive tomorrow.

Thank you for all the comments and advice.



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Guest Anonymous


good job Evan- congrats:

first 50 miles most critical. no lugging, no rpms over 4k, blip up to rpm levels- no sustained rpms keep varying.... follow bmw owners manual break in guide for 1972/73/74- they change a bit but are pretty good. i just had my valves reset and everything felt perfect. seating has gone well. compression is even. valves are tight. my builder said to use quaker state 10-30 oil for first 500. he wanted a thinnner oil. i now have valvoline 20-50 n for the next 1000 miles, then synthetic. no particular matter fooiund in drain. justr drive city stuff. you wont get into trouble that way. avoid freeway prolonged same rpm stuff, and keep the revs below 4 k until 200 miles. my engne has seen 4500 rpm under load in 3rd gear a few times, but shift up immediately. my break in went well- still going on. i guess lots of theories about this -i followed builder's recommendations and used bmw guide for reference. best, jay///

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Guest Anonymous

When you had the head rebuilt, did you have the top of the top cover machined along with the vaive cover. but thats only if you had the head machined or ground.

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Guest Anonymous

cover wasn't shaved. I've now taken that cover off three times and I can't tell you how frustrated I am. It's like I'm so close, but not close enough. I'm itchin to start my break in and with that much oil dripping, not such a good idea. The waiting is killing me.

I've been using the True Blue RTV and it's still leaking. To clean off the surfaces I used brake cleaner and a clean cloth.

Maybe because the top timing chain cover is too tall it's jacking up the seal on the bottom.

What are my options if it doesn't seal up?

I'll fire her up again tomorrow and see how much leakage I have.

Wish me luck.



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Guest Anonymous

is about to be broken in, but can't start until I take care of those pesky oil leaks from my top timing chain cover. It's driving me crazy. I just want to drive my car!!!

I heard that you car chirp your tires going into 2nd and 3rd gear. I can't wait to get a ride. One day I'll do it.


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Guest Anonymous


i put a different head on my sahara and the upper timing cover is just too tall and so there is a very small leak at an upper corner, the lower cover has a micro crack, so a very small leak there. only way to remedy this is to have head height and upper cover height made equal, either through shotgun method of looking and trying many covers, or machining the cover you have to fit the head. i dont know if that is typically done, but seems to be the way to go unless you can get ahold of a few covers and bring them to the engine for test. also, maybe the form a gasket stuff would do a better job than the rtv. I will loook at what we used - i forget now ( over year) but it was a wurth product , i think.

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Guest Anonymous

cover now and it's working much better, although the leak has switched positions to the other side of the timing chain cover. will the leak ever stop? seems like i'm chasing the leak from side to side, it's a serious pain. this morning i felt like not working on my car for a couple of weeks. my motivation is dwindling with not being able to drive my car.

heres to the rtv sealing everything so i can drive!



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