Deformed valve stem tip

Discussion in 'Street/strip 400/430/455' started by B-rock, Apr 27, 2018.

  1. B-rock

    B-rock Well-Known Member

    decided to inspect my rocker shafts. (71-455) I found the aluminum rockers had scored the shafts. So new heavy duty shafts with steel rockers from TA was ordered. I inspected my valves and found indentations on one of the tips. As well as wear on the corresponding steel rocker tip. Unknown miles on the engine. It may have had a valve job on it before but not sure. I have no idea how long the rockers have been user or if ever replaced. The overall health of the engine seems to be pretty good all things considered.
    I’m hoping to pick up a little performance and better idle with the new rockers. What should I do with that valve? In the long run I would like to go with a rebuild and aluminum heads. I rarely drive the car more then 1500 miles a year.
     

    Attached Files:

  2. hugger

    hugger Well-Known Member

    File it and go, I wouldn't expect any noticeable performance increase
     
    B-rock likes this.
  3. BUICKRAT

    BUICKRAT Got any treats?

    You may have a bad lifter...
     
  4. Schurkey

    Schurkey Silver Level contributor

    Pull the valve, have a machinist grind the tip. This will reduce the tip height, which is not desirable, but acceptable within limits especially for a near-stock engine. The alternative is to replace the valve.

    You could play games with a stone and trying to polish it by hand. Not my first choice.

    Overall, doesn't seem to be a huge amount of wear. I've seen WAY worse.

    Don't expect the engine to run any different.
     
  5. Bluzilla

    Bluzilla a.k.a. "THE DOCTOR"

    X2, .... Well Said.
    I would never advise cobbling the tip by hand. Don't forget these are shaft mounted rocker arms so it will not conform to the plane of the tip if its not 100% square with the stem. That would be a good way to waste a perfectly good New rocker arm in short order. Even if it were a stud/ball mounted rocker you wouldn't see us do it. I agree with Schurkey that the valve should be "tipped" by a competent machine shop or replaced.
    There is always the option of a full valve job on both heads, but with the cost incurred for all the time, machine work, and materials, you may want to consider the aluminum heads now.

    Larry
     
    Last edited: Apr 28, 2018
  6. Stevem

    Stevem Well-Known Member

    Visit your local race engine builder and see if he has a spare 3/8" lash cap stilling around you can by.
    Shops that deal a lot in Mopars are your best bet, or those who deal a lot with motors that also use 3/8" valve stems like BB Chevys and of course Buick.

    Also many shops that do flow testing all the time have lash caps sitting around.

    If need be grind it down so it sits on the top of the valve, NOT the keeper!
    Install and drive!
    If need be buying a full new set of 3/8" lash caps will be far cheaper cost wise then yanking a head to have that valve topped off or replaced, no less far less work!
     
    Last edited: Apr 29, 2018
  7. Bluzilla

    Bluzilla a.k.a. "THE DOCTOR"

    I believe Lash Caps have a few very good useful purposes, ...... I feel correcting a damaged single valve tip is not one of them. Lash caps can be used on titanium valves that may have no hardened tip, applications with 6mm-7mm (or any small diameter) valves to increase the tip surface for big cams with correct geometry, to help correct (lengthen) the installed height of excessive ground valve stems/valves proud on the seat, or geometry correction.

    If you were to add a lash cap and expect it to stay in place on one valve, the tip should undamaged, flat, 90* true to the stem before hand.

    Valve lash caps are normally available in .060-.080 thickness. That in itself would require at the very minimum a shorter pushrod (or full set if installing 16 caps), ...... but more importantly the lash cap would ultimately raise the valve tip installed height by the thickness of the cap (throwing the geometry off) which is one of worst things you can do to an already un-adjustable valve train ( in stock configuration).

    In my opinion, ...Though this may not be a High Performance Build situation, I feel it should still be addressed correctly as stated in Schurkey's responce.

    You could use the single lash cap in a situation where the damaged valve is tipped-(correctly machine ground) the same as the thickness of the cap being used, as long as the installed height of the valve tip ends up correct, though that seems as it may be an excessive amount for a standard Buick 3/8" valve due to its narrow margin between the tip and the lock groove (with the possibility of the tip breaking off).

    Larry
     
    Last edited: Apr 29, 2018
  8. Stevem

    Stevem Well-Known Member

    With stock and a hydro lifter if installing a lash cap does not bottom out the lifter plunger when things are bolted back up then that all that matters .
    Most lash caps I have used/ seen are .060" thick and the stock GM preload is about .030", figuring in ware on 50,000 plus mile motor that eats up that fresh factory .030" preload, a .060" cap should fly!
     
  9. Schurkey

    Schurkey Silver Level contributor

    Changing effective valve tip height will also change the rocker pad-to-valve tip contact area. Same as if you've sunk the valve doing a valve job, so the tip is too high.

    Depending on how accurately the valve tips were placed to begin with, this could be "no big deal" or a wear/geometry issue. Clearly a stock, low-rpm engine will be more forgiving.
     
  10. Mart

    Mart Gold level member

    I would turn valve so rocker tip rolls over new area.
    Your shafts are worn and the aluminum rocker i.d.''s will be worn as much if not more. Inspect the i.d.'s.
     

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