I.D my cam

Discussion in 'Cams, Heads and Valve Trains' started by Unforgiven, Mar 1, 2019.

  1. Loves302Chevy

    Loves302Chevy "One test is worth a thousand expert opinions."

    I thought as you did about installing new lifters on a used cam - it is actually the WORST case scenario for failure. C'mon Grumpy, add the link and pictures.
  2. Grumpy

    Grumpy The Grumpy Grease Monkey mechanical engineer. Staff Member

  3. Unforgiven

    Unforgiven Well-Known Member

    SEE #3

    What causes a camshaft to fail?

    A: We’ve gotten that question (or something very similar) a lot. We’ve also heard a lot of questions about camshaft installation and break-in procedure. Since proper installation and break-in go hand-in-hand with camshaft success or failure, we’ve decided to tackle it all in one post. In conjunction with the Summit Racing tech department, we’ve assembled the eight most common causes of camshaft failure:

    1. Lobe wear
    Lobe wear is often caused by improper lubrication during installation.

    Use only the manufacturer recommended lubricant, which is generally included with the cam. This lubricant must be applied to every cam lobe surface, and to the bottom of every lifter face of all flat tappet cams. Roller tappet cams only require engine oil to be applied to the lifters and cam.

    Also, apply the lubricant to the distributor drive gears on the cam and distributor.

    2. Improper Break-In
    After the correct break-in lubricant is applied to the cam and lifters, fill the crankcase with fresh, non-synthetic oil. Use motor oil with an engine break-in additive (ZDDP or ZINC camshaft additive), especially with flat tappet camshafts.

    Prime the oil system with a priming tool and an electric drill so that all oil passages and the oil filter are full. Preset the ignition timing and prime the fuel system. Fill the cooling system. Start the engine, run it between 1,500 and 3,000 rpm, varying the rpm up and down in this range for 20 minutes. During break-in, verify that the pushrods are rotating, as this will show that the lifters are also rotating. If the lifters don’t rotate, the cam lobe and lifter will fail. Sometimes you may need to help spin the pushrod to start the rotation process.

    3. Old Lifters with a New Cam
    You can use new lifters on a good used cam, but never pair used lifters with a new cam.

    If you are removing a good used flat tappet cam and lifters and are planning to use them again in the same (or another) engine, you must keep the lifters in the order they were removed from the cam they were on. Lifters “mate” to their specific lobes and can’t be changed. If the used lifters get mixed up, discard them, install a new set of lifters, and break in the cam again.
  4. Indycars

    Indycars Administrator Staff Member

    Does the above hold true when the cam and lifters are going into a different block (same make and model) that is
    going to have some slight variations in dimensions and geometry ?

    For the price of flat hydraulic lifters, I think I would go with new ones.
    Last edited: Mar 3, 2019
  5. Grumpy

    Grumpy The Grumpy Grease Monkey mechanical engineer. Staff Member

    a new block is going to result in minor valve train geometry issues,if you use old lifters in a new block.
    so yes the old lifters should get pitched in a dumpster and replaced with new lifters,
    Obviously if the old cam looks to have any wear issues both cam and lifters need to be replaced as a set.
    Last edited: Mar 4, 2019
  6. Loves302Chevy

    Loves302Chevy "One test is worth a thousand expert opinions."

    Grumpy, now you are going to make me search for it. OK, fine.

    Unforgiven, yes I have read #3 before, but I disagree. A used cam lobe has lost it's taper, and used lifters have lost their crown.
    Both are necessary when new to make the lifter rotate, with the contact patch between lobe and base as great as possible.
    After some miles, after both have worn in, the only thing keeping the lifter rotating is the offset of the cam lobe in relation to the lifter.

    worn10.gif Camlobed.jpg

    From your site Grumpy - notice the Rotation - Zero (22a) picture just above. The used and worn (but still good) cam lobe has no taper.
    Put a new lifter (with it's crown) on that lobe and you have a very narrow contact patch smack dab in the center of the lifter = NO ROTATION!
    No rotation means an early death for that camshaft and set of lifters! Now I know that some will say they have gotten away with doing this in the past (and I have too). You probably did it with only one lifter. YOU GOT LUCKY! Would you be willing to gamble that you could get away with it for all 16 lobes?
  7. Unforgiven

    Unforgiven Well-Known Member

    302, You are correct in your reply.

    You have shown why a new lifter on a worn cam will cause failure.
    BUT, as stated. You can install a new lifter on a GOOD used cam.

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