Bad valve sounds

Discussion in 'Classic Mustang Specific Tech' started by mustang70, Dec 10, 2003.

  1. Last night I readjusted the valves on my motor. I loosened them all up and retorqued them to 20 ft-lbs. I think that might be a little much, but I can't find any specs on it. So I go to start it and it sounds like I have a solid lifter cam. Something I noticed was that I was able to push some of the lifter plungers down like there was no oil in them. I didn't think too much of since it's been about a week since I started the motor. I have plenty of oil pressure, 40 psi at 1000 rpm. When it gets warm the pressure drops to about 20-25. I never noticed the engine getting tight when I was spinning it to do the valves. So I don't think there's any valve contact. I'm thinking I might have gotten a bad batch of lifters. Any ideas?
     
  2. This is a hydraulic lifter camshaft right?
    Okay, 20 ft.lbs. is probably not enough to overcome the self-locking feature of the rocker nut. the rockers are probably loose.
    Back off the rocker arms one cylinder at a time with the piston at TDC on the compression stroke until they are very loose, and slowly begin to tighten down on the rocker arm nut while spinning the pushrod. As soon as the pushrod gets stiffer to spin, you're at zero lash. Tighten the nut down 1/2-3/4 turn further and you're done.
    Make note of where the rockers were adjusted before and after doing this and compare. Was there a difference??
     
  3. Yes, it's a hydraulic cam. I know I had it tight before because it wasn't near this noisy. Although looking at the rockers it seems like they're moving more now. I just hope I haven't had any piston to valve contact. If I have the time after I get done with my Mountaineer I'll see what I can do about the rockers. I didn't think this type of arrangement had a locking feature. I thought they just got torqued down.
     
  4. Do you have an adjustable or non adjustable hydro valve train? More importantly, are you sure on which one it is? The reason is that they want to deal with each is different. On adjustable you want to tighten the rocker arm bolt until u can't/barely spin the push rod, then do another 1/4 turn. After that get some old valve covers and cut rectangular hole in the top and place them on your heads. Start your car, and loosen the rocker arm bolt until it starts to "chatter", then tighten it until it stops, then do another 1/4 turn. If you have a non adjustable then all you need to do is torque them to 24 ft/lbs and you should be good to go. I would still start it and see how it runs. Also do a compression test to make sure that they aren’t too tight.

    -Shaun
     
  5. It's a non-adjustable valve train. It's the stock style from 70. I have to make sure the lifter is on the base of the lobe before I can torque it right?
     
  6. Ya, the lifter needs to be on the base of the lobe.

    -Shaun
     
  7. I pulled the driver side valve cover off and found one of the rockers totally loose. I went ahead and tightened all of them and started it. It was running nice and smooth. So I took it around the block. By the time I got it back I could the tapping again. I think the nut might be wore out. I would have checked it tonight, but the motor was a little hot for my taste at that point. The next time I get a few minutes I'll pull the valve cover off and take a look. Thanks for the help guys.
     
  8. I had similar problems years ago (18 to be exact) running a hot cam 292 .525 with stock valve train. The high spring rate and high lift actually lifted the press in studs from the heads.

    If you don't have screw in studs, you may want to check and make sure the stud supporting the rocker arm that keeps coming loose isn't higher than the rest.

    Symptoms:
    Ran fine for a while, then started running roughly and lots of valve noise.
    Removed valve covers - several rocker arms were loose

    I removed all the rocker arms from one side and put a straight edge accross the top of all of the studs. It was clearly visible that several studs had become unseated.
     
  9. Thanks for the advice I'll check that out the next time I have it apart.
     
  10. Are you going on the Fire Relief toy run on sunday?
    it's on the westcoast board.

    PB
     
  11. I didn't know about the drive. I'll be coming home from Havasu Sunday. It's probably the last time I'll see my family before I leave.
     
  12. If he's talking about the rockers on a 70 model small block, then they are non adjustable. The rocker studs starting sometime in the 68 model year are the "positive stop" type and are tightened down until the nut contacts the shoulder on the stud. Some of the cam companies sell kits to convert them to adjustable, by using thick washers under the nuts.