Over Head Cam engines.

centermass556centermass556 Senior MemberPosts: 3,509 Senior Member
Any words of wisdom for working on them?
"To have really lived, you must have almost died. To those who have fought for it, freedom has a flavor the protected will never know."

Replies

  • TeachTeach Senior Member Posts: 18,429 Senior Member
    Some of them have very close clearances between the pistons and the valves, with absolutely no room for error where cam timing is concerned. I always align the timing marks according to the service manual directions and lock the camshaft(s) in place with vise grips before disassembling anything. Once the timing belt is loose, valve spring tension can cause the cam to snap into a different position and bend some valves. I use 2 pairs of locking pliers against the cylinder head to prevent movement in either direction. Never, ever try to turn the crankshaft with a cam belt or chain disconnected, as one piston/valve contact is one too many! 3 or 4 valve per cylinder engines are really bad about piston/valve contact problems.
    Jerry
    Hide and wail in terror, Eloi- - - -We Morlocks are on the hunt!
    ASK-HOLE Someone who asks for advice and always does something opposite
  • TeachTeach Senior Member Posts: 18,429 Senior Member
    I just wrote a long reply and hit a wrong key and lost it. If you're disconnecting the timing chain or belt for any reason, lock the camshaft(s) with two pairs of Vise Grips against the cylinder head to keep it from rotating in either direction, as spring tension can cause the cam to snap around and bend valves from contacting the pistons. Never, ever turn the crankshaft with the cam drive disconnected, and align all the timing marks before unbolting anything. Lots of OHC engines are "interference" engines where piston-to-valve contact can bend the valves if anything gets out of time. 3 or 4 valve per cylinder engines are exceptionally troublesome about bending valves due to timing problems.
    Jerry

    OK, it came back! You've been warned twice!
    :jester:
    Hide and wail in terror, Eloi- - - -We Morlocks are on the hunt!
    ASK-HOLE Someone who asks for advice and always does something opposite
  • centermass556centermass556 Senior Member Posts: 3,509 Senior Member
    The 3.7 I. The jeep is an OHC. I'm gonna start with the driver side. I did some reading and question asking on few forums and some have said I may have a rocker arm outta place.
    I'm trying to imagine how that can happen...but I'm gonna grab a Haynes and get at it in the next week.
    "To have really lived, you must have almost died. To those who have fought for it, freedom has a flavor the protected will never know."
  • JLDickmonJLDickmon Senior Member Posts: 1,726 Senior Member
    lets hope.. Everyone that uses that engine from Chrysler to Mitsubishi to Isuzu has TSB's published on the valve seats falling out of the head..
    Never laugh at your wife's choices.
    You are one of them.
  • jbp-ohiojbp-ohio Senior Member Posts: 9,596 Senior Member
    JLDickmon wrote: »
    lets hope.. Everyone that uses that engine from Chrysler to Mitsubishi to Isuzu has TSB's published on the valve seats falling out of the head..

    From what I'm reading.......... that is only if you badly overheat the engine.
    "The democracy will cease to exist when you take away from those who are willing to work and give to those who would not." Thomas Jefferson
  • jbp-ohiojbp-ohio Senior Member Posts: 9,596 Senior Member
    I think I may get one these to look for internal problems. You should be able to see a dropped valve thru the spark plug hole......

    31554_1318431962.JPEG
    "The democracy will cease to exist when you take away from those who are willing to work and give to those who would not." Thomas Jefferson
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