Register now to get rid of these ads!

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.

    Joined: Jul 26, 2019
    Posts: 6


    The title pretty much says it all, I know all about how it’s good for the life of the cam and what not, so I’m not asking about why you should break it in at 2500 for 20 mins, I’m asking what would happen if you just decided not too? What damage would it actually cause? How much can you turn over the engine before starting it and have it not be a huge deal? Thanks.
  2. liliysdad
    Joined: Apr 1, 2013
    Posts: 98

    from Oklahoma

    I think it depends on the cam profile and spring pressure. A stock or mild cam, and its likely nothing at all will happen. As the ramps get more radical, and spring pressured become more exaggerated, break in becomes more and more important.

    I you think every new car built from the dawn of motordom until the death of the flat tappet cam was broken in? Of course not.
  3. Back in the '60's I didn't even know what breaking in a cam meant. I just slid the buggers in, dipped the lifters in STP, fired her up, set the timing and adjusted the valves and hit the road. Never had a failure.
    Deuces, RICH B, Joe Travers and 23 others like this.
  4. Bird man
    Joined: Dec 28, 2009
    Posts: 741

    Bird man
    from Milwaukee

  5. Never did in the old days and had no grief; but now kinda wonder about the metallurgy/quality of new cams.
  6. Torana68
    Joined: Jan 28, 2008
    Posts: 1,320

    from Australia

    For the sake of 20 min I’ll stand there to look after an expensive cam. Std cam std springs probably not an issue but I’d probably still do it to reduce the chance of having to replace a cam .
    Oh and no , not killed one but we always did the run in thing when I was rebuilding for a living.
  7. Jerry A Smith
    Joined: Feb 11, 2017
    Posts: 3

    Jerry A Smith

    about 10 minutes into my last break-in, I wondered this same thing but then I called my brother and my dad and they guffawed at the idea of not doing it. "WTH wouldn't you?" So rather than fly in the face of prejudicial opinion, I let the motor go 10 more minutes. I have another coming up in a week or two due to external factors :eek:, so I doubt I will defy my folks and will undoubtedly let this be answered by others. Do I know what would happen if you didn' i do not.
    that being said I've only broke in 3 motors anyway, 2 were full rollers and one a flat tappet. I would worry some about break-in material getting loose on the first drive and a port getting plugged while I'm sitting at a light. perhaps the answer is that I'd be embarrassed while pushing my truck through the intersection.
    Hotrodjohn71 and Thor1 like this.
  8. George
    Joined: Jan 1, 2005
    Posts: 7,522


    Yup! The car is assembled, a "parker" fires up the car, drives as fast as he can (payed by the car) to the nearest parking spot & shuts it off. But the break in period is a best practice thing, why risk skipping it?
  9. I never even heard of this practice before the internet...:rolleyes:

    Had never done it on all those engines over the years. Just fire it up and go. Was more concerned with seating the rings.
    They were stock or mild performance rebuilds though...
  10. I've done about 40 or 50 with no losses. One parts store threw in a tube of cam lube, it wasn't a gimme like it is today.

    I always knew to give them a rudimentary break in and have refined it since. Big changes I've made were to pre oil, dump the oil and filter right after and use a conservative lash adjustment for the break in.
    Deuces, pitman, Hotrodjohn71 and 3 others like this.
  11. Jmountainjr
    Joined: Dec 29, 2006
    Posts: 1,435


    These days I am not sure why you would not take the time to do the recommended run in period. The materials, tolerances, oils, cam profiles, etc. just are not the same as it was in the 70's when you may have gotten away with not doing it. I would guess today the chances are more likely to get a flat lobe. Look how many guys have had a cam go south quickly after doing a break in run. If you want to skip it buy a roller and you will most likely be money ahead in the long run.
  12. Truck64
    Joined: Oct 18, 2015
    Posts: 5,316

    from Ioway

    Are camshaft blanks or whatever, are there American manufacturers still producing them, or is it a matter of overseas. Does Isky make their own stuff? Or just grind them.
    Deuces and Thor1 like this.
  13. Baumi
    Joined: Jan 28, 2003
    Posts: 2,869


    I always break them in 20 min @ about 2k rpm. Never had one fail but one. I have to admit it was a cheap enginetech grind and I even don´t blame it on the cam, I think the lifter material was jsut way to soft compared to a OEM lifter.
  14. I believe if you do a little reading here on the hamb you will see were a member recently flat spotted his cam by not braking it in. HRP
  15. dreracecar
    Joined: Aug 27, 2009
    Posts: 3,258

    from so-cal

    All it takes is once
    Deuces, Blues4U, Hotrodjohn71 and 3 others like this.
  16. Truck64
    Joined: Oct 18, 2015
    Posts: 5,316

    from Ioway

    That's what she said!
    Deuces likes this.
  17. sunbeam
    Joined: Oct 22, 2010
    Posts: 5,609


    The word flat sticks out. As far as the old days I've been doing 2000 rpm for 20 minute thing sense the 60s
    Last edited: Jun 29, 2020
  18. xsquiden
    Joined: Jul 20, 2009
    Posts: 112


    Anymore I always break them in I had one go south on me after they really started making the new oil crap I really don't know if it does any good but I'm not in the mood to tear an engine down completely to clean it just because I wouldn't spend 20 minutes running it in but to each there own.

    Sent from my SM-J327R4 using The H.A.M.B. mobile app
  19. xsquiden
    Joined: Jul 20, 2009
    Posts: 112


    The last engine I got to overhaul was a 351c friend got it cheap supposedly only 1000 miles on overhaul lol about half the lobes were visibly roached and just as many lifters the inside of the engine looked like strippers had an overnight drunkfest in there there was glitter everywhere.

    Sent from my SM-J327R4 using The H.A.M.B. mobile app
  20. Jmountainjr
    Joined: Dec 29, 2006
    Posts: 1,435


    I suppose if you are just against a run in period, your chance for success is directly related to how much attention you paid during assembly to the lifter bores, honed bores as needed, checked lifter fit in bore, matched lifters to specific bores for best clearance, and if after priming the oil system with the intake off you rotated the engine to insure all lifters were rotating in their bores.
  21. I think the main reason why it's so highly recommended these days as opposed to the '50's and '60's is that stuff is different these days. Crappy dinosaur oil has been replaced with hi tech stuff that doesn't work well for breaking in flat tappet cams, metal and its origin is suspect at best. Quality control ain't what it used to be. Take every precaution you can. It's a new world out there.
  22. Budget36
    Joined: Nov 29, 2014
    Posts: 8,423


    It does make you wonder a bit, did all auto manufactures run the engines for 20 minutes before factory roller cams?
    Deuces and Hotrodjohn71 like this.
  23. Joe H
    Joined: Feb 10, 2008
    Posts: 1,150

    Joe H

    Don't know about the assembly lines running them in, some of the engine assembly plants might have spun them. They had oil made for flat tappet cams, and likely used a break-in additive.

    Since you just came out of your cave, oil formulas made a change back on 2007, since then, flat tappet cams have been having problems. This was about the same time the extreme cams came out.

    Please post video's when you tear it back apart for lifter noise.
    Deuces and olscrounger like this.
  24. olscrounger
    Joined: Feb 23, 2008
    Posts: 4,516


    It's a crap shoot! Some guys spin em with no plugs til they see oil pressure then fire em up. I always follow the ritual and have had good results. Why chance it
  25. oldtom69
    Joined: Dec 6, 2009
    Posts: 578

    from grandin nd

    the problems aren't with the cam or lifter quality-it's oil quality!OEM aren't putting in roller cams out of the kindness of their hearts-the oil is bad enough they have to-if they could save a penny per car ,they would!tThey took out all the important additives in oil to make our lives safer-hows that working for them now!LOl
    Deuces, Hotrodjohn71 and alanp561 like this.
  26. seb fontana
    Joined: Sep 1, 2005
    Posts: 7,443

    seb fontana
    from ct

    I can read something else into the do or don't break in. If an engine idles at say 800 rpm then the lifter face/cam lobe see X amount of pressure opening the valves. If the engine is brought up to 2400 rpm right away won't the cam lobe/lifter face see more pressure? Maybe not by 4 times but by some increase which means un mated parts have more load on the contact/pressure points at the higher rpm. I think the building of oil pressure/flow is key. .
    Deuces and Hotrodjohn71 like this.
  27. birdman1
    Joined: Dec 6, 2012
    Posts: 1,370


    That was me! I definitely did break in the new cam and lifters like the manufacturer wanted.
    Deuces and Hotrodjohn71 like this.
  28. Budget36
    Joined: Nov 29, 2014
    Posts: 8,423


    Well, for those that say the problem is with the oil, if you put in the additive, use the break in oil, etc. Why the need to then run it in for 20 minutes.

    I'm just trying to make a point, I break them in as well too and even earlier than 2007, it was what I was taught to do.
  29. Elcohaulic
    Joined: Dec 27, 2017
    Posts: 2,491


    We just ran them for a few hours on the street, headed back home changed the oil and filter once and that was it.. I do remember them saying don't keep it at the same rpm during the first couple hours of use..
    I use to put a can of Rislone in the first oil change but that was it.. The oil back then was crap too.. Loaded with wax.. Oil today is so much better..
    Deuces and Hotrodjohn71 like this.
  30. I even had a cam lose some lobes in my Corvette over a year after a rebuild. Comp Cams was nice enough to replace it but I think its more than oil, I think the steel is different also.

Share This Page

Register now to get rid of these ads!


Copyright © 1995-2021 The Jalopy Journal: Steal our stuff, we'll kick your teeth in. Terms of Service. Privacy Policy.

Atomic Industry
Forum software by XenForo™ ©2010-2014 XenForo Ltd.