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Technical What would happen if you simply didn’t break in a flat tappet cam?

Discussion in 'The Hokey Ass Message Board' started by KEVIN SODERBLOM, Jun 28, 2020.

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  1. I'm a paint guy that happens to build his own engines, so you can understand my ignorance, but how does starting the engine and bringing it up to rpm for 20 minutes do anything more than "seat" each lobe and lifter together? If the cam has a soft spot in it, or a lifter was pushed into the bore without confirming it would spin freely, i really don't understand how the process "prevents" a cam from wiping out a lobe. Does it magically harden the lobes and lifters? personally i believe it comes down to spring pressure being more than Chinese cam blanks can handle, or a lifter that is stuck and in turn grinds down the lobe, but then again, i paint cars :D
     
  2. akoutlaw
    Joined: May 13, 2010
    Posts: 1,258

    akoutlaw
    Member

    I was schooled years ago that the lifters are minutely convex in shape on the base that mates with the cam, 2000 rpm plus keeps the lifter rotating around on the cam lobe & this lets the lobe & lifter seat in together. If you idle the motor too long there is a chance that the lifters will not rotate & therefore could take a flat "set" & cause the flat lobe condition which ruins both the cam & lifters. I have always run a new cam at 2000+ rpm for 20 min varying the rpm occasionally & haven't had a failure so I guess that I will keep on doing it this way. ;)
     
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  3. Ericnova72
    Joined: May 1, 2007
    Posts: 595

    Ericnova72
    Member
    from Michigan

    Nearly all the V8's we hotrodders and muscle car guys use and love are all splash oiled at the cam to lifter interface....no pressure fed oil passage directly to each cam lobe. RPM well above idle insures there is plenty of oil being flung off the rotating crank due to both higher oil pressure than you'd have at idle and by crankcase windage.
    For a long time in the 1950's and mid to late 1960's many connecting rods even had oil spurt slots or holes off the cap-to-rod split that faced in towards the cam to spray additional oil to that cam and lifters. Small Journal SBC is a prime example.
    Spurt holes were discontinued when emissions regulations started to spring up...those spurt holes also crated more windage to be sucked up by the now closed-loop PCV systems and they also sprayed the cylinder walls, leading to more burned oil also affecting emissions.
    At this same point in time, cam failure started to increase....anybody else remember all the flat cam problems Chevy had in the early-to-mid 1970's that were all in the '68-up large journal engines who's rods no longer had spit holes....I bet myself and a couple friends fixed 2 dozen of those as a high schooler in the 1980's.

    You're right though, you got to mind your P's and Q's with this....no burrs in lifter bore, all lifters rotate as cam is turned by hand, swap slow turning lifters with fast turners during this test to try to get them all rotating decently, ZDDP in the oil blend, good cam lube on the lifter foot and lobe, as little dead cranking on the starter as possible.
     
  4. I’m with Lloyd on this, I can’t my head around what it is actually gaining from the 20 minute run in but I do it anyway as I hear it’s recommended . I get the higher revs,the more pressure and flow but that’s about it.
    I use cam lube,prime the oil pump with a drill til the rockers bleed and use an addictive for start up, but honestly I thought this would be enough.
    Shame is I generally like to understand why I should do things,not just because I hear it.
     
  5. southcross2631
    Joined: Jan 20, 2013
    Posts: 4,413

    southcross2631
    Member

    I installed my first cam in 1965 when I built my first small block Chevy. A 1958 283 that I was building for my first 55 Chevy.
    I had watched my dad build countless engines. He always used STP on the bearings and cam shaft and lifters. He never ran one in at 2,000 rpms he just cranked it up set the timing and turned the idle up to about 800 rpms and watched the oil pressure and temp while we bolted the hood on.
    Then he would go drive it and accelerate from about 40 to 70 in high gear about 10 times to seat the rings. He never had one smoke, knock or lose a camshaft . So I followed his procedure on street cars.
    On race cars it was different . A machinist told me the clearances were there and that running in a motor was not needed and he would just crank one up and set the timing and bring it up to temp. and wing the shit out of it. He said if it didn't blow up in the first 2 minutes it would be good . Right or wrong his motor's set a few national drag race records.
    As a line mechanic in the 80's I started seeing some flat lobed cams start to show up especially late 70's early 80's 305 GM engines. Replaced them with parts store cams and no problems. That's when I started breaking in cam and lifters. Have not had one go flat on break in . I have bought some really nice GM cars cheap with flat lobed 305's because people did not want go to the expense of fixing them
     
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  6. AldeanFan
    Joined: Dec 12, 2014
    Posts: 892

    AldeanFan

    I’ve a friend who recently lost a cam even after doing a 20min break in so it’s no guarantee.

    I put cam break in in the same category as using a torque wrench on lug nuts. I’m sure lots of guys don’t and survive but every once in a while it will bite you in the ass and you’ll wish you had.

    20 minute break in is a great time to drink a beer and admire your work.


    Sent from my iPhone using Tapatalk
     
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  7. Joe H
    Joined: Feb 10, 2008
    Posts: 1,525

    Joe H
    Member

    All these stories from years bad are irrelevant, THE OIL FORMULAS HAVE CHANGED!
    Camshaft profiles are also different creating more loading on the ramps of the cam lobe.

    IF YOU ARE USING STOCK CAMSHAFTS WITH STOCK SPRING PRESSURES, break-in is not nearly as critical. Throw in a extreme cam with heavy spring pressure, you might get 4 or 5 minutes of run time without a proper break-in.

    High rpm is to insure plenty of oil is thrown off the crank on to the camshaft since there is NO oil pressure on cam lobes. The 20 minute duration is seat the lifter and lobes.
     
  8. Your engine idles @700 revolutions per minute give or take a hundred. it is not likely you are going to turn it over one minutes worth while you are putzing around with it.

    I am going to assume that the question has to do with lack of knowledge of what cam break in is or why it is done. So here is the simple answer, cam break in burnishes the cam lobes and lifter faces and matches them to each other.

    You may get lucky and you may not by driving it without break in. Most likely not, if for no other reason you really don't want to run that cam break in lube through your engine any more than you really have to. Cam break in lube has grit in it a lot like valve lapping compound. Usually by the end of break in it is washed completely off the cam and gets dumped when you change the oil.
     
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  9. I’m getting close to breaking in my 289...I’m second guessing my choice of oil...I was ordering some parts and saw Jeg’s had their own break in oil..so I ordered it up. I can’t find any info other than the reviews on their page. It does contain Zinc and say’s no other additives needed. But I did see an article about the amount of Zinc in different break in oils and Lucas was the run a way champ...now that being said, I know plenty of folks that use Brad Penn, Royal Purple, Comp Cam, etc...it’s one of those “I can save a buck” but is this the right thing to save a buck on..I also saw that it may be re labeled comp cam oil...and That’s what I’m running so...last motor I broke in was in the late 90’s and used Valvoline VR1 and some GM additive..fingers crossed this goes well..
     
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  10. blowby
    Joined: Dec 27, 2012
    Posts: 8,661

    blowby
    Member
    from Nicasio Ca

    Go to the front of the class.
     
  11. T.L.
    Joined: May 24, 2011
    Posts: 209

    T.L.
    Member
    from Colorado

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  12. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 5,216

    2OLD2FAST
    Member
    from illinois

    The pressure a spring is capable of exerting does not change with r.p.m. most of the oil provided to the cam lobes/ lifter faces is from splash of the crank , hence the need for 2000 + - rpm to provide adequate lubrication .
     
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  13. I dunno... as soon as I came to the statement that a Mechanical Engineer is the most qualified to test oil, components, etc., I tuned him out. Too damned arrogant and self absorbed for my taste. I've learned more from 'common folk' who had common sense than any self-back-patter I've ever mat. Take his long-winded ' free advice' with a grain of salt. YOMV
     
  14. nrgwizard
    Joined: Aug 18, 2006
    Posts: 2,516

    nrgwizard
    Member
    from Minn. uSA

    Too bad you didn't finish reading the blog/whatever-it-is, even though it's hard to follow. You'd've learned something - that everything isn't as it seems, or as advertised, & can be mostly tested to find out. He gives his testing procedures, incl the ones he tried at 1st that didn't work. He buys the oil himself to test. Some surprises in there on oil quality - both on dino-juice n synthetics - & he names them(unlike most bitch threads on here that you almost never find out who the bad-actor is). It is worth the read.
    Marcus...
     
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  15. Thanks... I'll go back and try to wade through it.
     
  16. BamaMav
    Joined: Jun 19, 2011
    Posts: 6,709

    BamaMav
    Member
    from Berry, AL

    I read through a lot of that, and from what I can tell, you pick a brand and weight and take your chances. Some test better, but in the real world use you'd probably not be able to tell the difference on our older engines. Most of us don't use our old engines for daily drivers, so yearly mileage will be much lower. Any good quality oil should meet our needs. I've had good luck with Pennzoil through the years, so I'm sticking with it. Your experience may differ.
     
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  17. Blues4U
    Joined: Oct 1, 2015
    Posts: 7,589

    Blues4U
    Member
    from So Cal

    Boy is that guy full of himself. Sorry, I couldn't get past 5 minutes of his blathering. This isn't the first time his blog has been brought up around here, as I recall he had some bad info in there. He may be a mechanical engineer like he claims, but he isn't a lubrication engineer.
     
  18. 1971BB427
    Joined: Mar 6, 2010
    Posts: 8,717

    1971BB427
    Member
    from Oregon

    Prior to any internet, and back in the 60's I rebuilt my first engine. A SBC in my '57 Chevy. I was working at the local Cadillac dealership, so asked what I should do when setting ring gaps, sizing bearings, or anything else I should be aware of? The answer always included making sure I broke in the cam/lifters for 20 minutes at 2500 or higher rpm. I was told to only shut it off if it got hot, and continue after the engine cooled off until the 20 min. was achieved.
    So this "myth" isn't something started by the internet. And every engine building book(s) I own specify cam breakin times for flat tappet, and they're all old books too.
     
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  19. Blues4U
    Joined: Oct 1, 2015
    Posts: 7,589

    Blues4U
    Member
    from So Cal

    Yes, this isn't anything new. I wasn't building engines in the 60's, but I was in the 70's, and this was old news at the time. As several others have mentioned, cams are splash lubricated, and the higher rpms ensure adequate flow of oil to the cam surface. But I believe there is more to it than that. Now it's time for me to blather on a little about a topic I know very well, it is how I've made a living for the past couple of decades.

    Lubrication of sliding surfaces are lubricated under different regimes known as boundary lubrication, and hydrodynamic lubrication. Hydrodynamic lubrication refers to the condition where a wedge of oil forms at the entrance to the load zone between the cam and the lifter (or any other moving parts, i.e. the rings and the cylinder walls for example). The oil is drawn into the load zone due to shearing of the oil molecules as the parts rotate. As the oil enters into the load zone the viscosity of the oil increases many times until it is almost the consistency of a solid. This causes a separation of the moving parts so that the asperities on the surfaces do not make contact. But it takes movement of the parts to create this condition, hence the "dynamic" part of the word hydrodynamic.

    A common analogy used to illustrate this is water skis. If you've ever water skied you know that before the boat starts pulling you just float in the water trying to keep the ski positioned in front of you. When the boat starts pulling you the ski starts to rise up onto the surface. If it's a slow start you might get dragged for 20 - 30 yards or so and get a face full of water. If it's a fast start, or your a little kid, you pop right up. That's the same type of forces at work. You get the engine rpms up quickly and build that hydrodynamic wedge in front of the load zone and the parts are separated and kept from making contact. Over years of testing engineers and engine builders determined that roughly above 2000 rpms is enough speed to do the job.

    Below the speed required to build the hydrodynamic wedge the lubrication regime that exists is called boundary lubrication, and the parts will make contact, and wear will occur. This is where the anti-wear additives, like zinc, come into play, they form a self sacrificing layer, called a tribo film, on the metal surfaces so that when the surfaces make contact you have additives riding against additives rather than metal against metal, which reduces or prevents wear from occurring. But on brand new parts no tribo film exists to protect the parts, it has to be built up, and that requires heat to activate the zinc compounds and cause them to form the film. That's why the 20 minute procedure, give it enough time in hydrodynamic conditions for enough heat to form on the surfaces to develop a tribo film, so that when you start the engine back up after shutting it down, the film will protect the surfaces until the oil starts flowing and splashing up onto the surface of the cam.

    I won't get into the elasto hydrodynamic regime, but that is what occurs with rolling conditions, like when the tip of the cam rolls past the lifter. If you're interested you can google up the term and I'm sure there is plenty of information out there to find on it.

    So, enough blathering about geeky lubrication stuff, but I hope that explains the "Why" part of the break in practice. With all of that said, I built and I assisted other mechanics build many diesel engines when I worked for a heavy equipment dealer prior to being drafted into the lubrication business. I must've been involved in over a hundred over the years. And we never broke them in. The process was to connect all of our test equipment like tachs and boost gauges, etc, fire the engine up, check for oil pressure, check for leaks, if everything is good we brought it up to temperature in about 5 minutes of loading it in torque converter stall condition and hydraulic stall condition, and once up to temperature we ran a full set of diagnostic tests to record a baseline for future reference. If the engine wasn't performing within expected specs we'd make any adjustments needed. Then shut it down, retorque the head, pull an oil sample, and reassmble all the sheetmetal around it and put it to work. And it wasn't baby'd at work, it was expected to go out and do a full days work and earn it's pay. We'd recommend an early oil change at about 100 hours instead of the normal 250 (these days our customers are changing oil at up to 1000 hrs). And that was it. The break in was done under full load conditions.
     
    Last edited: Aug 27, 2021
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  20. Budget36
    Joined: Nov 29, 2014
    Posts: 13,174

    Budget36
    Member

    ^^^^ Very informative!
     
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  21. ekimneirbo
    Joined: Apr 29, 2017
    Posts: 4,216

    ekimneirbo


    The quotes above all point out in different ways the need for the lifter base and the cam lobe to "seat-burnish-wear in-etc" to each other. Anyone who believes that this is a myth can do a simple experiment that will demonstrate that "mating the parts together" establishes a working relationship that is very important. Once you have broken your engine in, and you know the engine is working properly with no metal in the oil.........pull some of the lifters out and put them in different holes. Then just drive your engine normally and see what happens.

    Now, there is enough "known" cases of people reinstalling cams and mixing the lifters that someone doesn't really need to repeat the process to prove what happens.....but if you are one of those people that has to prove it to yourself then go for it.

    For those that wish to say that they followed every direction properly during assembly and broke their engine in as reccomended......and it still failed...........Well there are certain things that can happen other than not mating the lifter/lobe interface properly. One big cause is a lifter that sticks and doesn't rotate, wrongly radiused lifters, poor metalurgy or even inadequate oil supply (even though you revved the engine). All of those factors will ruin the cam and lifter no matter whether you break the engine in properly or not. Another way of saying it is that proper break in will help solve one problem........lifter to cam mating. It will not necessarily be a cure for the other issues that can ruin cams and lifters.
     
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  22. I don't imagine that roller lifters alone save the OEMs any money.

    But, by design, flat tappet cams are somewhat limited in areas such as rate-of-lift. Roller cams can have much more aggressive valve opening and closing rates. Roller cams give engineers more flexibility and another means of increasing power and maybe lowering emissions as well.

    And if I remember correctly, roller cams take less power to turn in the engine than flat tappets. Hard to pass up free horsepower, I guess.
    :rolleyes:
     
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  23. jaracer
    Joined: Oct 4, 2008
    Posts: 2,419

    jaracer
    Member

    I was in tech school in the 60's and properly breaking in a cam was a topic that was brought up. I remember an article by one of the engine parts suppliers titled "The Most Important 15 Minutes of an Engine's Life". It dealt with breaking in the cam and lifters.
     
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  24. proartguy
    Joined: Apr 13, 2009
    Posts: 658

    proartguy
    Member
    from Sparks, NV

    Cams going flat is nothing new I had an Olds 324 and a Cad 331 that developed flat cams in the ‘60s. Cam break-in instructions are not a internet issue they were advised on aftermarket cams in the mid-60s as I recall.
     
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  25. Blues4U
    Joined: Oct 1, 2015
    Posts: 7,589

    Blues4U
    Member
    from So Cal

    You are correct. The number 1 biggest driver for changes in cam's and followers is emissions regulations, closely followed by fuel economy requirements, and then meeting ever increasing market demands for more power. They didn't go to rollers because they had to because of changes in oil, they did it for the reasons you mentioned.
     
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  26. It seems that the roller lifter would need the same lubrication needs on start up as the flat tappet?
     
  27. Blues4U
    Joined: Oct 1, 2015
    Posts: 7,589

    Blues4U
    Member
    from So Cal

    There's no sliding wear with a roller, it's all rolling motion, different lubrication regime in play, elasto-hydrodynamic lubrication. Same as with a roller bearing vs a plain bearing.
     
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  28. I'm talking about the added splash factor, doesn't the roller require lubrication? And it's also not pressurized
     
  29. Do regrind also follow the golden rule ?
     
  30. I've always done my "break-ins" by varying the RPMs, usually driving leisurely on city streets, stopping for stop signs and red lights, slowing for turns, pulling away with just enough throttle., etc. At first, once in a while, hold a gear and maybe bump 2500rpm for a moment and then let it drop down. And after a few dozen miles, do the same cycles bumping 3500rpm or maybe holding it a longer moment. An hour or so of that or the "I can't stand any more of this" feeling, whichever comes first, is just about the right amount of break-in.
     
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