Adjusting Valve Lash
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Instructor
Joined: Mar 2005
Posts: 151
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From: Somewhere, Delirious
Adjusting Valve Lash
I found a good article and how-to on valve lash adjustment for Chevrolet small blocks and big blocks..
http://www.centuryperformance.com/ad...h-spg-149.html
http://www.centuryperformance.com/ad...h-spg-149.html
Advanced
Joined: Aug 2007
Posts: 83
Likes: 0
From: Cambridge Ohio
I'm in the process of readjusting my valves after roller rocker arms and valve spring upgrade. I checked the Century method against the Comp Cam method and they both appear to put the valve being adjusted on the bottom of the base circle. Also, with the spark plugs out, I was able to rotate the motor easily with a 15/16" socket on the alternator pulley nut. Thanks for the link!
Le Mans Master
Joined: Mar 2004
Posts: 5,107
Likes: 171
From: Dublin CA
This is the standard Chevy adjustment method used for years. I have adjusted valves using this for about 40 years and at times when your fingers are covered with oil it is difficult to "feel" the spinning of the rod. This was especially true when I installed the SuperRam, the #1 and #2 cylinders were very difficult to get my fingers around the pushrods (roller rockers installed).
Form Member Joe C came up with another method that I have since used and prefer. There is no doubt as you pull on the feeler gauge, you can see and feel when the play has been eliminated. Here is the write up Joe C presented to the Forum.....
BTW, I tried something a little unconventional on adjusting hydraulic lifters. one thing that always bothered me is the statement "spin the pushrod until resistance is felt" that seems a little too subjective to me. so I tried this: I set "zero" lash with a .0015" feeler gauge while slowly turning the adjusting nut. when I felt the feeler gauge grab, I was fairly confident I was about .001 from zero lash. at that point, I turned the adjusting nut 3/4 turn. I recently read that one turn is equivalent to .040" because of the thread pitch on the threaded rocker arm stud, so 3/4 turn should give you about .030" adjustment. I also read that within a hydraulic lifter there is .060 total plunger movement, and ideally you want to be just about in the middle of that range, or .030 inch. I don't know if I’m out in left field on what I did, but I feel I got a really consistent valve adjustment across the board. if you think you might have a tight cylinder, maybe give this a try - it seemed to work for me...
again, thanks for all your help - take care -
JoeC
Form Member Joe C came up with another method that I have since used and prefer. There is no doubt as you pull on the feeler gauge, you can see and feel when the play has been eliminated. Here is the write up Joe C presented to the Forum.....
BTW, I tried something a little unconventional on adjusting hydraulic lifters. one thing that always bothered me is the statement "spin the pushrod until resistance is felt" that seems a little too subjective to me. so I tried this: I set "zero" lash with a .0015" feeler gauge while slowly turning the adjusting nut. when I felt the feeler gauge grab, I was fairly confident I was about .001 from zero lash. at that point, I turned the adjusting nut 3/4 turn. I recently read that one turn is equivalent to .040" because of the thread pitch on the threaded rocker arm stud, so 3/4 turn should give you about .030" adjustment. I also read that within a hydraulic lifter there is .060 total plunger movement, and ideally you want to be just about in the middle of that range, or .030 inch. I don't know if I’m out in left field on what I did, but I feel I got a really consistent valve adjustment across the board. if you think you might have a tight cylinder, maybe give this a try - it seemed to work for me...
again, thanks for all your help - take care -
JoeC
Thread Starter
Instructor
Joined: Mar 2005
Posts: 151
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From: Somewhere, Delirious
Although, after re-reading JoeC's segment, I couldn't help but wonder, did he mean 1 full turn as opposed to 3/4 of a turn? .030 is the optimum plunger depth, yes. So, with the feeler gauge "grabbed" at .001 above lash, 3/4 turn would only bring the plunger depth to .020.
Either way, I like the sound of that method better from the get-go, but I think I'll be making 1 full turn after the "grab", for whatever it's worth..
Either way, I like the sound of that method better from the get-go, but I think I'll be making 1 full turn after the "grab", for whatever it's worth..
Le Mans Master
Joined: Mar 2004
Posts: 5,107
Likes: 171
From: Dublin CA
I use zero lash plus 3/4's of a turn....always have. Using Joe's method, I still use the 3/4"s and have had no problems even running the cam that I have and the lifts with the 1.6 roller rockers.
You place the feeler gauge between the rocker and the valve stem. As you start to tighten the nut you pull on the gauge. You can easily feel when it starts to bind. There is no question about....did the rod really stop rotating even with oil on my fingers....
......or have I passed that point?
Try it, you will like the results.
You place the feeler gauge between the rocker and the valve stem. As you start to tighten the nut you pull on the gauge. You can easily feel when it starts to bind. There is no question about....did the rod really stop rotating even with oil on my fingers....
......or have I passed that point?Try it, you will like the results.
Racer
Joined: Feb 2005
Posts: 338
Likes: 49
From: Quincy,Illinois
Although, after re-reading JoeC's segment, I couldn't help but wonder, did he mean 1 full turn as opposed to 3/4 of a turn? .030 is the optimum plunger depth, yes. So, with the feeler gauge "grabbed" at .001 above lash, 3/4 turn would only bring the plunger depth to .020.
Either way, I like the sound of that method better from the get-go, but I think I'll be making 1 full turn after the "grab", for whatever it's worth..
Either way, I like the sound of that method better from the get-go, but I think I'll be making 1 full turn after the "grab", for whatever it's worth..
