HI everyone,

I am getting many conflicting ways to break in my new C6! Does anyone know that proper way how to break it in and what mileage I should be at when it is broken in?

~Kieley

 

Well you well get a multitude of answers and possibly even start a flame war Just ignore everyone else and listen to me. Or better yet, listen to the engineers who designed your C6:

Breakin period is 500 miles. During that time, take it easy on the car and brakes. I try to keep my new cars below 3000 rpm during this period. I do have a few weak moments but I try to limit them. Try to keep your speed below 60 mph. That may be tough while in the freeway. Do the best you can. This is for the transmission and ring and pinion gears. Several heating and cooling cylces are supposed to help anneal the ring and pinion gears. You are also supposed to vary your speed during the breakin period too. I change my oil at 1000 miles or so to remove any metal filings etc that can be present in a new motor.

There will be people who brag about driving it hard from the beginning. It's their car and their business. But you have absolutely nothing to loose by following GM's reccomended break in procedure.

 

Go to the General Discussion section and click on the sticky FAQ thread....there is a long thread in there about it...

 

Owner's manual says essentially what need-for-speed said, but also says no full-throttle starts those first 500 miles. Also, no hard stops the first 200 miles.

 

Minor Quibble: Annealing is not the correct word. The heat cycling is used to heat treat and polish the gear surfaces. Annealing softens metals.

 

well as long as we're quibbling, thats incorrect too.
http://dictionary.reference.com/search?q=anneal
annealing is also used to harden materials as well.

 

agree with need for speed and silver coupe.

when i took custody of the c6, i was talking shop with the owner of the dealership who actually is a fellow gearhead & weekend racer- i asked him about the break in period. his response? "beat the snot out of it from day one, that's what we have warranties for. if it breaks, bring it back in & we'll fix it"

i think i'll listen to need for speed & silver coupe.......

 

if anyone else in the service department shares those sentiments I think youve just found a place to avoid,
even for something as simple as an oil change. im sure if he got
into a major accident with his new C6 with 100 miles on it,
hed just say "oh well, thats what we have insurance for."

 

From my metal working book: Quote: (spelling errors mine)

Anneal: When not preceded by a descriptive adjective, annealing consists of heating to and holding at a suitable temperature, then allowing to cool. Annealing removes stresses, reduces hardness, increases ductility and produces a structure suitable for formabilituy.

Full Anneal: This term is synonomous with annealing and is used to differentiate anneal from bright anneal, stress relieve anneal, etc.

Spherodize anneal: This treatment is similar to full anneal except that the steal is held at an elevated temperature for a prolonged period of time, followed by a slow cooling inorder to promote a microstructure whereby carbides exist in a globular spherodial form.

Soft anneal: When maximum softness and ductility are required steel should be ordered soft annealed.

Stress relieve anneal: Stress relieving is intended to reduce the residual stress imparted into the steel in the drawing operation. It generally consists of heating hte steal to a suitable point below the critical temperature followed by s slow cooling.

Bright anneal: This process consists of annealing in a closely controlled furnace which permits the surface to reamin relatively bright.

UnQuote: and some other heat treatments ReQuote:

Normalize: Normalizing consists of heating to a suitable temperature slightly above the critical temperature at which point the grain structure is affected, followed by cooling in still air to room temperature. This produces a uniform structure and hardness throught.

Quench: Quenching consists of heating the steel above the critical temperature, then hardening by immersion in an adgitated bath of oil, water, brine, or caustic. Quenching increases tensile strength, yeild point, abd hardness. It reduces the ductility and impact resistance. By subsequent tempering some ductility and impact resistance can be restored.

Temper: Tempering is the heating of steel, after quenching, to the specified temperature below the critical range, then aior cooling. It is done in furnace, oil or sault baths, at temperatures varying from 300dF to 1200dF. Lower temperatures give maximum hardness and wear resistance.

UnQuote.

Based on this: I submit that the correct word is TEMPER.

Nothin of the quoted material above indicates that annealing is used to harden anything.

 

Drive it like you stole it!!!!!

 

When I went through the Bowling Green Assembly Plant two weeks ago I asked one of the men on the engine line. His response was "break it in at any speed you want, just don't give it too many WOT starts in the first 500 miles, and to vary the speed so that the gear train can mesh at varying loads. . .it doesn't matter if you do it at 55 or 125 as long as you vary the speed."

 

No offense, but taking the advice of a guy on the assembly line on engine break in makes about as much sense as trusting your car salesman's advice on the subject. Listen to the guys that DESIGNED the car. Or just read the owners manual.

 

While I agree that we should follow the owners manual I do have a question as to the speed restriction. While I can understand the varying of the speed and no WOT and easy on breaks I dont get the under 55 MPH restriction - I would think RPM restrictions would make better sense - is the 55 MPH restriction more for the suspension?

I always thought it was a way to ensure if wheels came off due to bad assembly you had a chance to walk out of it :-)

 

I always wondered about the same thing. I figured all that mattered was RPM. Great minds must think alike Then I read here that the MPH limitation is for the ring and pinion gears and the transmission. Makes sense to me.

p.s. I never thought about the wheels coming off. After problems with inconsistent (and high) torque on the C5 lug nuts from the factory (which was suspected of leading to warped brake rotors), I now check the torque on the lugnuts of all new cars I bring home.

 

That's the problem with using a general dictionary for a techincal term, the answer is often wrong. Annealing, as related to carbon steels and cast iron has a specific technical meaning. It *never* means hardening.

Annealing steel requires that its temperature be raised above the critical point (1200-1300 F depending on alloy), then slowly cooled to room temperature. The rate of cooling through the critical point determines the particular properties of the annealed steel, and there are particular modifying adjectives used with the term "anneal" to denote that.

Note that no steel component in the drivetrain of a car should ever reach the critical temperature in normal use. So annealing should never occur in a car.

To harden steel, it must be quenched. This process requires the steel's temperature to be raised above the critical point, then *very* rapidly cooled below the critical point by immersing the part in oil, water, or brine. A rate of temperature change on the order of 1,000,000 degrees per second is required to achieve full hardness in steel. Steels that have been quenched are glass hard and very brittle. Tempering is required to *draw back* the "temper" of the metal so that it can be used in machinery. Otherwise, it will shatter when loaded.

Tempering temperatures range from 400 to 700 F depending on the carbon content of the particular steel. Raising a piece of steel to the proper temperature in that range, and holding it there for a specified time, alters the properties of the steel, making it less brittle. Tempering can't soften steel as much as annealing. In other words, even a dead blue tempered piece of steel still retains much more hardness than an annealed piece.

Now heat treatment of non-ferrous metals is very different. For example, brass requires quenching to be fully annealed. Aluminum is hardened by being held for extended periods at temperatures which would be suitable for tempering steel. Etc. It is a very complex and techincal subject.

All that said, any designer who depends on the end user to do the final heat treatment of a part is an idiot. Heat treatment always causes a part to change dimension. Any critical fits must then be *ground* to final dimension before the part is fitted into a machine. Thus heat treatment (hardening, annealing, or tempering as required), is always done at an intermediate point in manufacture *before* final assembly.

The main reasons for a break in period are to allow parts, primarily gears, to *wear* together. Gears as machined never mesh perfectly. They have to be run together for a time in order for the tooth profiles to mesh perfectly. This is the source of the tiny metal particles you find in the oil of a new engine, transmission, or differential. Once perfect mesh has occured, further wear is reduced sharply, and the gears will have a long life. But during the break in period, gears wear very rapidly, and can gall or chip if abused. That's why you want to run them easy until perfect mesh has been achieved.

Note that followers on cams, rings in bores, etc, also require a period of time to wear together to achieve perfect mesh. This has nothing to do with an in car "heat treatment", and everything to do with running in the parts for perfect mesh. Once run in, the parts will have very smooth surfaces that conform perfectly to the mating surfaces of their mating parts. This *full contact* spreads mechanical loads, and prevents stress concentrations which would cause failures or accelerate wear.

Since galling is always a hazard while running in parts, special assembly lubes and gentle loading are required during the break in period. In the old days, the first oil change had to be done early to remove the assembly lubes and the metal wear particles from a new engine. Today, Mobil 1, and other synthetics, can double as assembly lubes, and today's filters are much more effective at catching particles. So today we don't need to do an early oil change. We do still need to operate at reduced loading for the first few hundred miles to let the parts run in properly. Since the contact pattern of gear teeth varies with varying loading, we also want to run the car at various speeds and loadings during break in to assure that a full contact patch has been achieved.

 

It is a matter of load. Higher speeds require more force to push the car through the air. That translates to a higher torque requirement on the drivetrain, and more force on the mating faces of gear teeth. While running in the teeth, you don't want a lot of force, or the tooth faces could gall, which causes gear noise, stress concentrations, and accelerated wear throughout the life of the gear train. You want the gears to run in together to a perfect mesh, then you can put high loads on them with little danger of premature failure.

 

Did a quick search on Google for engine break-in and found this on a gm site, not specific to the C6, but for GM crate motors:

http://www.gmpartsdepot.com/572startupinst.html572 Start-up and Break-in Procedures


1. After installing the engine, ensure the crankcase has been filled with 20w50 racing motor oil (non-synthetic) to the recommended oil fill level on the dipstick. Also check and fill as required any other necessary fluids such as coolant, power steering fluid, etc.

2. The engine should be primed with oil prior to starting. Do this by using an engine oil priming tool. If you do not have one, one can be obtained through GM, part number 12368084. Follow the instructions enclosed with the tool. This is the sure way to get oil to the bearings before you start the engine for the first time. Also, prime the engine if it sits for extended periods of time. See short block instructions, GM part number 86962927, for further information.

3. Safety first. If the vehicle is on the ground, be sure the emergency brake is set, the wheels are chocked and the car cannot fall into gear. Verify everything is installed properly and nothing was missed.

4. Start the engine and adjust the initial timing. Set the ignition timing to 20° before top dead center (BTDC) and the engine idle to 950 RPM (ZZ572/620) or 1200 RPM (ZZ572/720R) with a timing light and the vacuum disconnected and plugged. Rotate the distributor counterclockwise to advance the timing. Rotate the distributor clockwise to retard the timing. Leave the vacuum advance disconnected.

5. When possible, you should always allow the engine to warm up prior to driving. It is a good practice to allow the oil sump and water temperature to reach 180°F before towing heavy loads or performing hard acceleration runs.

6. Once the engine is warm, set the total advance timing to 36°F at 4000 RPM.

7. The engine should be driven at varying loads and conditions for the first 30 miles or one hour without wide open throttle (WOT) or sustained high RPM accelerations.

8. Run five or six medium throttle (50%) accelerations to about 5000 RPM and 55MPH (if application is a vehicle), and back to idle (0% throttle) in gear.

9. Run two or three hard throttle (WOT 100%) accelerations to about 5000 RPM and 55 MPH (if application is a vehicle), and back to idle (0% throttle) in gear.

10. Change the oil and filter. Replace with 20w50 racing motor oil (not synthetic) and a PF35L AC Delco oil filter. Inspect the oil and the oil filter for any foreign particles to ensure that the engine is functioning properly.
11. Drive the next 500 miles under normal conditions or 12 to 15 engine hours. Do not run the engine at its maximum rated engine speed. Also, do not expose the engine to extended periods of high load.

12. Change the oil and filter. Again, inspect the oil and oil filter
for any foreign particles to ensure that the engine is functioning properly.

13. Do not use synthetic oil for break-in. It would only be suitable to use synthetic motor oil after the second recommended oil change and mileage accumulation.

 

Sure hope you don't think that just because this came off the internet that it's appropriate here, especially no. 13. Do you know of any car manufacturers that recommend this breakin?

 

I stand corrected.
Its definitely something that cannot be done properly in the dynamic environment of an engine, so
I doubt those parts are intended to change to their final metallurgical properties on the fly.

 

That all makes sense shopdog. I always try to follow the manufacturer's breakin procedures and your info gives a good explanation of the logic behind those procedures. I do hope you will speak up in these "break in" threads because there will be more of them. And there will always be people who say "drive the hell out of it from day 1, that's they way my Daddy always did it".

Glad to hear that the heating and cooling cycles aren't important because I will most likely be doing Museum Delivery on my C6 and it's 850 miles from BG to my home.