Valve Lash
Thread Starter
Instructor
Joined: Apr 2004
Posts: 157
Likes: 1
From: Woodstock on
Valve Lash
Hello All,
I have a set of hydraulic non roller lifters in my 86. I am using aftermarket roller rockers. I rebuilt the engine and set the valve lash by tightening the rocker while rotating the push rod until I felt resistance. Then I gave the adjustment nut 1/2 turn to set the pre-load. The odd thing is that when I did a leakdown test, all the valves leaked. I loosened the valves back 1/2 turn and the leak stopped.
I am stumped on how to proceed. I used the valve lash method for years and have not had any issues. But it seems weird the valves leak if they are set properly. Any ideas?
I have a set of hydraulic non roller lifters in my 86. I am using aftermarket roller rockers. I rebuilt the engine and set the valve lash by tightening the rocker while rotating the push rod until I felt resistance. Then I gave the adjustment nut 1/2 turn to set the pre-load. The odd thing is that when I did a leakdown test, all the valves leaked. I loosened the valves back 1/2 turn and the leak stopped.
I am stumped on how to proceed. I used the valve lash method for years and have not had any issues. But it seems weird the valves leak if they are set properly. Any ideas?
Race Director
Joined: Aug 2000
Posts: 11,470
Likes: 764
Hello All,
I have a set of hydraulic non roller lifters in my 86. I am using aftermarket roller rockers. I rebuilt the engine and set the valve lash by tightening the rocker while rotating the push rod until I felt resistance. Then I gave the adjustment nut 1/2 turn to set the pre-load. The odd thing is that when I did a leakdown test, all the valves leaked. I loosened the valves back 1/2 turn and the leak stopped.
I am stumped on how to proceed. I used the valve lash method for years and have not had any issues. But it seems weird the valves leak if they are set properly. Any ideas?
I have a set of hydraulic non roller lifters in my 86. I am using aftermarket roller rockers. I rebuilt the engine and set the valve lash by tightening the rocker while rotating the push rod until I felt resistance. Then I gave the adjustment nut 1/2 turn to set the pre-load. The odd thing is that when I did a leakdown test, all the valves leaked. I loosened the valves back 1/2 turn and the leak stopped.
I am stumped on how to proceed. I used the valve lash method for years and have not had any issues. But it seems weird the valves leak if they are set properly. Any ideas?
with the engine in the #1 TDC (compression), adjust the following:
exhaust -- 1, 3, 4, 8
intake -- 1, 2, 5, 7
(this is my personal method) instead of "rotate the push rod while turning the adjusting nut," I use a .0015" feeler gauge, between the rocker arm and valve stem, slowly tighten the adjusting nut until the feeler gauge "grabs." at that point, you should be within .001" of zero lash. then adjust the nut 3/4 turn. this method seems a little more exact or precise than the "rotate the push rod" method, which IMO is a little too subjective. this should result in a more even adjustment across the board. either method will, however, work just fine.
now, rotate the crank 1 revolution or 360° and adjust the following:
exhaust -- 2, 5, 6, 7
intake -- 3, 4, 6, 8
i've been doing .0015" thing for over 10 years now without issues. basically, you set it and forget it.
Safety Car
Joined: Aug 2009
Posts: 3,751
Likes: 276
From: Melbourne, Victoria, Australia
for the adjusting sequence, follow the FSM --
with the engine in the #1 TDC (compression), adjust the following:
exhaust -- 1, 3, 4, 8
intake -- 1, 2, 5, 7
(this is my personal method) instead of "rotate the push rod while turning the adjusting nut," I use a .0015" feeler gauge, between the rocker arm and valve stem, slowly tighten the adjusting nut until the feeler gauge "grabs." at that point, you should be within .001" of zero lash. then adjust the nut 3/4 turn. this method seems a little more exact or precise than the "rotate the push rod" method, which IMO is a little too subjective. this should result in a more even adjustment across the board. either method will, however, work just fine.
now, rotate the crank 1 revolution or 360° and adjust the following:
exhaust -- 2, 5, 6, 7
intake -- 3, 4, 6, 8
i've been doing .0015" thing for over 10 years now without issues. basically, you set it and forget it.
with the engine in the #1 TDC (compression), adjust the following:
exhaust -- 1, 3, 4, 8
intake -- 1, 2, 5, 7
(this is my personal method) instead of "rotate the push rod while turning the adjusting nut," I use a .0015" feeler gauge, between the rocker arm and valve stem, slowly tighten the adjusting nut until the feeler gauge "grabs." at that point, you should be within .001" of zero lash. then adjust the nut 3/4 turn. this method seems a little more exact or precise than the "rotate the push rod" method, which IMO is a little too subjective. this should result in a more even adjustment across the board. either method will, however, work just fine.
now, rotate the crank 1 revolution or 360° and adjust the following:
exhaust -- 2, 5, 6, 7
intake -- 3, 4, 6, 8
i've been doing .0015" thing for over 10 years now without issues. basically, you set it and forget it.
Don't forget to prime the new lifters before fitting them , it doesn't take much to over adjust them. takes a bit of practice then you can never go wrong again.
Drifting
Joined: Mar 2018
Posts: 1,362
Likes: 400
From: DFW TX
I had a motor years ago give me fits with initial valve adjustments so I just started adjusting them with the free spinning to resistance method and then firing up the engine and adjusting them the rest of the way while she idled. Never had any problems after than except for a little oil clean up.
Le Mans Master
Joined: Aug 2017
Posts: 6,941
Likes: 1,490
From: New Jersey
I move the rocker until I can't feel it tap while tightening (basically just seating the pushrod against the lifter) then give her 3/4 turn. I did the adjustment while running a few months ago after that method and it was exactly half a turn until I just started hearing a light rocker tap while loosening.
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
Hello All,
I have a set of hydraulic non roller lifters in my 86. I am using aftermarket roller rockers. I rebuilt the engine and set the valve lash by tightening the rocker while rotating the push rod until I felt resistance. Then I gave the adjustment nut 1/2 turn to set the pre-load. The odd thing is that when I did a leakdown test, all the valves leaked. I loosened the valves back 1/2 turn and the leak stopped.
I am stumped on how to proceed. I used the valve lash method for years and have not had any issues. But it seems weird the valves leak if they are set properly. Any ideas?
I have a set of hydraulic non roller lifters in my 86. I am using aftermarket roller rockers. I rebuilt the engine and set the valve lash by tightening the rocker while rotating the push rod until I felt resistance. Then I gave the adjustment nut 1/2 turn to set the pre-load. The odd thing is that when I did a leakdown test, all the valves leaked. I loosened the valves back 1/2 turn and the leak stopped.
I am stumped on how to proceed. I used the valve lash method for years and have not had any issues. But it seems weird the valves leak if they are set properly. Any ideas?
Now for zero lash that is when you can roll the p-rod with your fingers but not move it up or down. Your really not looking for resistance but you want to identify when the p-rod is not going to move the valve or depress the lifter plunger yet has no slack between rocker arm and lifter cup.
Hope this helps.
BTW I use 1 full turn of preload.
Last edited by cardo0; May 29, 2018 at 11:22 PM.
Oil Producer
Joined: Apr 2014
Posts: 9,371
Likes: 2,736
joec's method is the shizzle.
i used this on the first engine i did and it served me well! i coated my feeler in oil it made the "grab" easier to feel. cheers and good luck
for the adjusting sequence, follow the FSM --
with the engine in the #1 TDC (compression), adjust the following:
exhaust -- 1, 3, 4, 8
intake -- 1, 2, 5, 7
(this is my personal method) instead of "rotate the push rod while turning the adjusting nut," I use a .0015" feeler gauge, between the rocker arm and valve stem, slowly tighten the adjusting nut until the feeler gauge "grabs." at that point, you should be within .001" of zero lash. then adjust the nut 3/4 turn. this method seems a little more exact or precise than the "rotate the push rod" method, which IMO is a little too subjective. this should result in a more even adjustment across the board. either method will, however, work just fine.
now, rotate the crank 1 revolution or 360° and adjust the following:
exhaust -- 2, 5, 6, 7
intake -- 3, 4, 6, 8
i've been doing .0015" thing for over 10 years now without issues. basically, you set it and forget it.
with the engine in the #1 TDC (compression), adjust the following:
exhaust -- 1, 3, 4, 8
intake -- 1, 2, 5, 7
(this is my personal method) instead of "rotate the push rod while turning the adjusting nut," I use a .0015" feeler gauge, between the rocker arm and valve stem, slowly tighten the adjusting nut until the feeler gauge "grabs." at that point, you should be within .001" of zero lash. then adjust the nut 3/4 turn. this method seems a little more exact or precise than the "rotate the push rod" method, which IMO is a little too subjective. this should result in a more even adjustment across the board. either method will, however, work just fine.
now, rotate the crank 1 revolution or 360° and adjust the following:
exhaust -- 2, 5, 6, 7
intake -- 3, 4, 6, 8
i've been doing .0015" thing for over 10 years now without issues. basically, you set it and forget it.
Thread Starter
Instructor
Joined: Apr 2004
Posts: 157
Likes: 1
From: Woodstock on
All good advice on how to adjust the rocker arm but that is not the question I was asking. Why do the valves leak if they are set correctly? Has anybody ever done a leak down test on their engine after adjusting the rocker arms?
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Race Director
Joined: Aug 2000
Posts: 11,470
Likes: 764
sorry - assumed the valves were too tight since when you loosened the adjustment, the leaking stopped -
. unless you have some sort of a valve face/valve seat issue, you shouldn't have leaking with the valves seated and correct adjustment.
Last edited by Joe C; Jun 2, 2018 at 01:30 PM.
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
What it appears to me is if you had to adjust the litter preload to stop valve leakby on a leakdown test the lfters were not adjusted correctly. It implies the valves were held open by overtightning/overadjusting the lifter/preload.
Safety Car
Joined: Sep 2004
Posts: 3,953
Likes: 550
From: Mission Viejo CA
Thread Starter
Instructor
Joined: Apr 2004
Posts: 157
Likes: 1
From: Woodstock on
Have not eaten crow in a while but have to now. My mistake was adding too much preload as stated.
I was adjusting the rocker arms to the point the where the pushrod would not rotate. Did it again until I just felt resistance and then added half a turn. Checked for leaks. All good.
Thanks for the assistance.
I was adjusting the rocker arms to the point the where the pushrod would not rotate. Did it again until I just felt resistance and then added half a turn. Checked for leaks. All good.
Thanks for the assistance.