What does "breaking in a cam" actually mean

I hear this term a lot and I'm not sure that I know what it means. How do you "break in"a new cam?

 

Run the new engine to 2000 RPM's for 20 minutes or so, you just broke in the cam. Done. That's how I was taught...

 

run the engine at 2500 rpm or more for the first 15 minutes or half hour. that way the cam always has oil thrown on it from the lower end, so it won't go dry and eat up a lobe, until the surfaces wear in to each other.

 

Ditto on the first two. Just did mine last year,ran at about 2300 for 20 minutes. Supposedly eliminates flat spots.

 

word on the street is to vary the RPM a bit for a better break in 2200-2500 or so should be good.

 

btw, roller cams (lifter) do NOT need to be broke in...

 

You're actually breaking in the lifters, not the cam. You're establishing a wear pattern on the bottom of the lifters (they spin while they move up and down). This is why you can use new lifters with an old cam (if you break them in), but you can't use old lifters with a new cam.

 

If it's a rebuild don't forget the break in process to seat the rings too.
Good Luck.

 

And pay close attention to the type of oil you use during the break-in period (not just the initial 20 to 30 minutes at 2K to 2.5K rpm). New formulations of oil have drastically reduced the ZDDP in oil and it's ruining cams and lifters in newly rebuilt older engines:

http://www.hotrod.com/techarticles/engine/flat_tappet_cam_tech/

 

Just to add to the above - the key is keeping RPM high (above 2000) during the first running to keep oil splash on the cam as they learn to like each other. Make sure engine is ready to run - timing, etc. - when it is first started - you do not want to shut off in the first 20 minutes. And oil is VERY important - modern oils do not have the friction modifiers that they used to because of gov't regulations - particularly Zinc. Add STP to the oil as a good source of zinc (also a good assembly lube). Racing oils, such as Valvoline VR-1, also have added zinc. Some people use Diesel oil or special cam break-in additive. Of course, higher spring pressures make this all the more critical. Flat tappet cam break-in is a real problem in racing classes requiring them - some sanctioning bodies are starting to allow rollers due to this oil issue. All the above is a good reason to use roller lifters, as all OEM's now do !!

 

If youve got a very high lift cam or choose to run a very aggressive spring, you shoudl consider breaking the engine in with a lighter spring then swapping them out. It is a pain in the ass but so is buying a new custom grind. Ive only had to do use this method a few times. Unless youre building a track only engine with 8000+ rpm capability it shouldnt be an issue, and by then youll know exactly what your spring rate is.

 

Shell's Rotella T diesel engine oil still has some of the good additives in it, and I've heard it recomended by a couple reputable sources. Throw in a bottle of Comp Cams break-in oil additive too, and you should be good. My local race shop will refuse to sell you a flat tappet cam unless you buy a bottle of Comp Cams additive along with it, so there must be something to it.

If possible, remove your distributor and spin the oil pump shaft with a drill to pre-lube the engine before fire-up. A 1/4" socket on an 8" extension will work for a SBF (I dunno about others).

I've been told NOT to use fully synthetic oils for break in, and maybe not at all for flat tappet cams. Seems they are TOO slipery, and there's not enough drag on the foot of the lifter to spin it. I don't know if this is BS or not, but it sounds like an easy risk to avoid even if it's only partially true.

 

run engine at varying speeds from 2000-2500 for first 30 min. Use shell rotella Diesel oil and add some GM EOS (engine oil supplement) to add the good stuff back in. if u have an OHV engine, pull valve covers during break-in to ensure that push rods (and lifters) are spinning in their bores. if they dont spin, your hosed.

Freddy

 

recently heard that the 'new' diesel oils have a lower ZDDP content due to the '07 emmision engines having CAT converters on 'em....seems using EOS or race oils may be the prudent thing to consider.

 

If you buy a new cam, look at the lobe surfaces, then look at the lifters and you'll have most of your answer. Two flat, raw surfaces. Use plenty of good assembly lube on the lobes and then use regular 30w to break it in. Synthetics are designed to prevent wear so they won't allow the cam to break-in properly. The additives are a good idea also. Be sure to change the oil as soon as the break-in is done to remove metal shaving, etc. I use a magnetic oil plug to monitor metal fragments, shavings. Be sure to follow the manufacturers recommendations. This is a critical time during the birth of an engine so be sure to stay with the motor and watch your gauges. There ya go!

 

Just as a side note, I've been running Mobil synthetic in my coupe motor (full race '59 390 Cadillac with custom regrind 500/300 cam) without any problems for about a year now. Knock on wood.

 

Something I have wondered about....for example....when a 1960 Chev was built, was the engine run at the factory to break in the cam before being delivered?
I can also remember when we had to start using unleaded gas and everyone said the lead was needed in older engines. Always wondered why engines run on butane lasted so long without the lead???

 

Yes, diesel oils have had to reformulate just like passenger car oils. But you can still find the older stuff. You're looking for CI-4 or CI-4+ rating - if you see CJ-4, it's the newer stuff with reduced ZDDP. Although I think it's still slightly higher than the passenger car stuff.

GM EOS or any of the major cam mfgr's break-in additives will have plenty of this stuff.

Be sure & change your oil & filter after break-in too.

 

Aman, Your only partly right on the surfaces. the cam lobe is a flat surface but it's ground on a 1 degree taper to facilitate the spinning of the lifter in operation. The lifter has a radiused base (not flat) for the same reason. When the two surfaces come in contact during running the combination , along with the fact that the lifter bore is offset to the centerline of the lobe, imparts a spinning motion to the lifter (and consequently to the pushrod) that minimizes wear to the valvetrain components by allowing them to mate together in a unique pattern. This is why you keep lifters in order when you tear down an engine so they can be reunited with their specific lobes when a cam is reused.

Frank

 

I was thinking the same thing.

So what's the result if a camisn't brokenin properly????

 

flat lobes on the camshaft=no valve action(not a good thing)=all that metal running thru the engine from the lobe(s).....

 

Re: 60 Chevy - much better oil in those days, and LOW spring pressures. Result of not "breaking in" a cam is really that the cam destroys itself during the breakin period - rounds off a lobe or two and you get to replace it !!!

 

What if I am going to use my old cam with new lifters? Any worries that I should be aware of?

55caddad

 

New cam + new lifters = good
Old cam + new lifters = good
New cam + old lifters = bad

the foot of the new lifters will wear-in to mate with your old cam lobes. Follow the same break-in process outlined above and you should be good.

 

if you buy a new cam it should come with the correct lube and instructions for breaking it in, like everyone has said run it above 2000 and not at a steady rpm but up and down keep your foot moving, brummm brum brum brummmm, lol. of all the cams i have broken in the last one was the worst, it was a new engine with no coolant in it yet, i filled it with water and waited for awhile to give it a chance to bleed any air out of the system, then i filled it again, started the engine and ran it above 2000 for about 10 min and it started to get warm so i had to shut it down, thermostat had stuck so i pulled it out, filled it with water again and fired it up, ran for about 10 min and it started to tap like crazy, had to shut it down, pulled the valve cover and found a bent pushrod, replaced the pushrod and fired it up again, ran for about 10 min and the tapping returned again, had to shut it down, same thing bent push rod. pulled the head and set it back to the shop and they cleaned up the valve guide and i reinstalled it and finished the cam break in. so just be ready for stuff to go wrong, if something happens shut it down fix it and start again.

 

I think it is when you grind a flathead cast iron cam to .450 lift, has about a .7 inch base circle, then you put double valve springs, it flexes too much and snaps in two . . . then drops into the rods and you throw a rod out the side of the block . . . Yes . . . that is what breaking in a cam is . . .

Just messing with yah . . .

Dale

 

Unless there's a problem like overheating or something else major, it's no real problem to stop the break-in. Like mentioned above, just make sure you get the total 20-25 minutes of break-in time on the cam at 2000-2500 rpm and it should be fine. Just never (NEVER) let the engine idle during those critical 25 minutes.

 

Everyone has pretty much nailed this one. All motor oils, including Diesel in 2007, have reduced the amount of ZDDP. Best to add a break-in boost to your oil (GM EOS, or other) for those first critical 20 minutes.

A minor correction about the reason you need to be at 2000 rpm: That's the point that the cam/lifter has the lowest load. Below that, the nose loads are very high (function of the valve spring); above 2500 or so (depends on cam profile) the loads are highest at the peak positive accels of the profile (inertia loads start to come in). So between those points, the nose loads are reduced and the speed is low enough where the inertia loads haven't come in yet. I recommend 2000 - 2200 for 20 to 30 minutes. After that, change the oil and run any good oil you want. I run synthetic after break-in, but that's just me.

 

I ran that oil in the 454 in my 55 and the cam went out after several thousand miles. Not sure if the oil had anything to do with it, but that cam seemed to go out a bit sooner than they usually do. I put a roller in to replace it.....

 

Lunati, good info, thanks.

but...

Wouldn't you want to have the zinc-additive in the oil at all times, especially with today's oils?