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Technical Camshaft break in

Discussion in 'The Hokey Ass Message Board' started by 70executive-Catalina, Sep 19, 2019.

  1. 70executive-Catalina
    Joined: Dec 20, 2018
    Posts: 51

    70executive-Catalina
    Member
    from Canada

    Hi,

    So I’ve been reading and watching lots of videos on how to do a camshaft break in. Now I have to questions:

    1. Is there a way to determine push rod length without actually using a push rod checker?
    I ask this because my current set up is old and, I would assume if the engine’s lifters and lobes are very worn.

    2. How do you set the timing when breaking in a cam? Comp Cams says lifters will mate to the camshaft and if that is the case then it will require manifold and distributor removal.
     
  2. birdman1
    Joined: Dec 6, 2012
    Posts: 658

    birdman1
    Member
    from USA

    just install the old pushrod in the engine, rotate the engine by hand, and when the valve is at full lift, the rocker should be very close to the center of the valve stem.
    #2- set the timing to factory specs to start with, then play with it until you get the best performance. as far as manifold removal question, please explain what you mean.
     
  3. 70executive-Catalina
    Joined: Dec 20, 2018
    Posts: 51

    70executive-Catalina
    Member
    from Canada

    Removing the manifold for dropping the lifters?
    Also aren’t I supposed to start it and bring it up to 2000-2500 rpm immediately? I’ve played with timing before but is it an issue to adjust timing during break in?
     
  4. flamedabone
    Joined: Aug 3, 2001
    Posts: 4,506

    flamedabone
    ALLIANCE MEMBER

    Tell me more about what you are doing and why. Is this a running engine? Are you having trouble starting it? Does it run like shit? Did you change the cam?

    Generally speaking, the pushrods that left the factory in the engine should be just about perfect unless you have changed something. Also, an assumption about how worn you engine may or may not be could be wildly inaccurate.

    Give us some details, we'll get this sucker figured out.

    -Abone.
     
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  5. 70executive-Catalina
    Joined: Dec 20, 2018
    Posts: 51

    70executive-Catalina
    Member
    from Canada

    467C6E70-FD69-4243-BE33-3335B9C96F53.jpeg 7E9B6928-668C-4C27-8B3F-2B2EE017EB1A.jpeg Well, I’d like to switch to full roller rockers (1.5) at some point but in the meantime I am putting in a higher duration and lift cam and mechanical lifters.

    Since the arms currently on it are stock I just want to make sure I break the cam in properly. The engine already runs fairly hot, despite having an aluminum intake.
    The idea of estimating or actually calculating pushrod length was just a time saving hope.

    But following that direction could you not calculate it based off cam lift, lifter length, spring height and tangent on the arm?
    I almost wonder if you could get it by Sin.
    Following angle A) with the length of the rocker and staying on the valve lock at 1/2 radius would be our point of max lift.
    B0A56522-EB57-40CA-BE69-D30D6FDE738C.jpeg 7E9B6928-668C-4C27-8B3F-2B2EE017EB1A.jpeg AD23085E-B7A4-4C6A-A5ED-4A36CE266DA4.png
     
  6. drtrcrV-8
    Joined: Jan 6, 2013
    Posts: 1,164

    drtrcrV-8
    Member

    Possibly you've never heard of the KISS Principle? If you buy(or make?) a pushrod checker, the checker will have been used & rusted away, & the motor will have 200K miles on it by the time you've finished all those calculations(& corrected your math errors?), & the motor won't care how much math you've done. The checker will take no more than an evening & will be more accurate due to less possibility of measurement & computational errors.
     
  7. flamedabone
    Joined: Aug 3, 2001
    Posts: 4,506

    flamedabone
    ALLIANCE MEMBER

    There is a small possibility you may be overthinking this.

    Unless your new cam has a much different lobe centerline, your original pushrods are going to be fine. I am going to ASS-U-ME your new cam is a mild to moderate performance grind somewhere around 480 degrees gross valve lift, maybe 280 degrees duration. I base this on very little information other than 480/280 is a pretty popular Chevvie cam profile. A cam of that category is going to be fine with the original pushrods. I am also going to ASS-U-ME that you have adjustable rocker studs, which if correct, will compensate for any minor differences in cam profile, compressed head gasket thickness, deck height, etc.

    My advise is to use plenty of break in cam lube, Valvoline NON-synthetic VR-1 race oil (high in zinc) and use a proper cam break in procedure and you will be fine.

    -Abone.
     
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  8. 70executive-Catalina
    Joined: Dec 20, 2018
    Posts: 51

    70executive-Catalina
    Member
    from Canada

    Yes I have hear of the KISS principal.
    Gene Simmons kicks all the dumbasses out of the band and becomes a millionaire due to intelligence.

    I live in BF nowhere Manitoba. I’m 2 hours away from a speed shop with a tool that I can buy. That means 4 trips ( 1 there 1 back for a tool and 1 there 1 back for the rods).

    If I can calculate the length I’m going to try that instead of tearing apart a motor and making lots of trips
     
  9. drtrcrV-8
    Joined: Jan 6, 2013
    Posts: 1,164

    drtrcrV-8
    Member

    You could do both over the phone(or computer) from Speedway in about 20 minutes(tops), save your time(& gas), & wait for the mail?? KISS was not about a heavy metal band, bur rather "Keep It Simple Stupid" : The simpler you keep it the less trouble it will give you!
     
    Last edited: Sep 19, 2019
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  10. Fordors
    Joined: Sep 22, 2016
    Posts: 2,170

    Fordors
    Member

    Have you put a hydraulic roller cam in the engine? Have you installed aftermarket aluminum heads? Have you put rocker arms with a different ratio on the heads?
    If the answers to the above questions are no then I would expect you will be OK with the factory pushrods.
     
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  11. flamedabone
    Joined: Aug 3, 2001
    Posts: 4,506

    flamedabone
    ALLIANCE MEMBER

    Why are you so worried about the pushrod length? Is there some detail that we don't know that has you losing sleep about it?

    -Abone.
     
  12. 70executive-Catalina
    Joined: Dec 20, 2018
    Posts: 51

    70executive-Catalina
    Member
    from Canada

    I just figured it out

    Inches:
    The Cam intake lift is 4.60,
    The Stud length I pulled with a measureing tape and it was a rough pull mind you. But if I’m wanting rocker arms @ 1.5 then we can use A2 + B2 =C2.
    7.3125 before cam lift.
    7.7725 inches with lift factor.
    That’s pretty dam close to stock.

    This gives us the distance from the rocker arm perched with no spring pressure.
     
  13. Rex_A_Lott
    Joined: Feb 5, 2007
    Posts: 968

    Rex_A_Lott
    ALLIANCE MEMBER

    ^^Reminds me of an old saying, “The figures don’t lie...but liars figure “.:D:)
     
    427 sleeper likes this.
  14. KISS and Gene Simmons !! KISS stands for ''Keep it simple stupid'' but thanks for giving me a good laugh, i don't think you are going to be a ''Millionaire'' any time soon.:eek: JW
     
    427 sleeper likes this.
  15. Just color the top of the valve tip with a dry erase marker turn, put the rocker arm on and adjust. Then turn the motor over 2 revolutions this will show you your contact area on the valve tip in relation to the rocker arm and tell you if the push rods are the right length or not
     
  16. 70executive-Catalina
    Joined: Dec 20, 2018
    Posts: 51

    70executive-Catalina
    Member
    from Canada

    I just wanted to save driving. I do appreciate the responses though.
     
  17. jaw22w
    Joined: Mar 2, 2013
    Posts: 837

    jaw22w
    Member
    from Indiana


    I am speechless!
     
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  18. 70executive-Catalina
    Joined: Dec 20, 2018
    Posts: 51

    70executive-Catalina
    Member
    from Canada

    Yeah, that was the measurement of arm height on the stud centered on the valve spring.
    I bet if you were to take a 1.6 ratio or 1.7 they would move down on the stud slightly in order to center it. As it is a 1.6 Ratio at 2.25 centered height usuing the same lift cam tells me an 8.08 rod is necessary.

    I wonder if someone does take a measurement of rocker stud position if that will hold true
     
  19. Just put the old fucking pushrods back in and follow what flamedabone said....


    Sent from my iPhone using H.A.M.B.
     
    Last edited: Sep 19, 2019
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  20. jaw22w
    Joined: Mar 2, 2013
    Posts: 837

    jaw22w
    Member
    from Indiana

    You cannot calculate pushrod length like that.
     
  21. 70executive-Catalina
    Joined: Dec 20, 2018
    Posts: 51

    70executive-Catalina
    Member
    from Canada

    Looks like I just did. After all pushrod geometry is calculated using a checker, which is just the missing side of a triangle.
     
  22. jaw22w
    Joined: Mar 2, 2013
    Posts: 837

    jaw22w
    Member
    from Indiana

    It's your engine. Have at it!
     
  23. flamedabone
    Joined: Aug 3, 2001
    Posts: 4,506

    flamedabone
    ALLIANCE MEMBER

    Building a running, driving hot rod is usually equal parts of thinking and doing. My suggestion is a little less think and a little more do.

    Good luck, -Abone.
     
  24. s55mercury66
    Joined: Jul 6, 2009
    Posts: 3,684

    s55mercury66
    Member
    from SW Wyoming

    I think you will need the rocker arm fulcrum point to calculate this, which may be kinda hard to determine. I guess I'll go search the net and see if I can find it.
     
  25. If you haven't changed from factory steel heads to aluminum heads, the push rod length should be fine, stock for a Chevy 350 is 7.794. Most aluminum head applications will be .100" over stock length. This is from when I was deciding on my push rod length.
    valve-001.JPG
     
  26. Mike51Merc
    Joined: Dec 5, 2008
    Posts: 3,786

    Mike51Merc
    Member

    An adjustable pushrod is $15.
     
  27. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 1,738

    2OLD2FAST
    Member
    from illinois

    You also need a solid lifter .......
     
  28. RmK57
    Joined: Dec 31, 2008
    Posts: 1,042

    RmK57
    Member

    You can use a hydraulic lifter. Take out the plunger and replace it with a short bolt then put the clip back in.
     

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