Rocker Adjustment
Dr. Detroit
Joined: Mar 2012
Posts: 10,095
Likes: 4,025
From: New Braunfels Texas
I go 1/2 turn as this generally pushes the plunger about .025......that .025 is a good number......cheater style Super Stock lifters plunge exactly this far.....and then stop. They are not noisy at .020.
Why do I not go any further? For the same reason that Super Stock lifters are .025......at very high RPM's, this keeps as little oil as possible beneath the plunger and helps keep the lifters from pumping up....which is always misdiagnosed as valve float. Valve float is when the springs cannot pull the valve back.....pump up just holds them open.
Is this critical on a street driven engine? Maybe not.....but I have done it like this for 20 years and the only time I deviate from it is when it is an offshore boat application.....in which case a 1/4 turn is where I put them.....why do I do this? Because an offshore boat coming in hot and then cutting off for no wake zone has a LOT of oil in the lifters to bleed off in about a second.....and my experience is that the engine will burble or stall......
Good info on the Howards cam card too......never seen that one.
Hope this helps.
Jebby
Why do I not go any further? For the same reason that Super Stock lifters are .025......at very high RPM's, this keeps as little oil as possible beneath the plunger and helps keep the lifters from pumping up....which is always misdiagnosed as valve float. Valve float is when the springs cannot pull the valve back.....pump up just holds them open.
Is this critical on a street driven engine? Maybe not.....but I have done it like this for 20 years and the only time I deviate from it is when it is an offshore boat application.....in which case a 1/4 turn is where I put them.....why do I do this? Because an offshore boat coming in hot and then cutting off for no wake zone has a LOT of oil in the lifters to bleed off in about a second.....and my experience is that the engine will burble or stall......
Good info on the Howards cam card too......never seen that one.
Hope this helps.
Jebby
Last edited by Jebbysan; Apr 9, 2018 at 09:50 AM.
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,809
From: Cool Northern Michigan
I think some people have the perception that if the lifter is, say, two inches tall, then the plunger inside must have at least an inch of travel. Nothing could be further from the truth. In reality, the plunger inside only has a 0.060 - 0.120 of travel. Keep in mind that 0.125 is a eight of an inch. Not much. If you crank down on that rocker nut a full turn, you could be at the point of bottoming out the plunger and there would be no give to the lifter. If you enjoy bending pushrods, or kissing the pistons with valveheads then, by all means, crank 'er down.
Last edited by HeadsU.P.; Apr 9, 2018 at 01:00 PM.
Team Owner
Joined: Jan 2007
Posts: 53,648
Likes: 878
From: Southern Cal Ca
St. Jude Donor '22
all said and done, i go 5/8's turn min
there is a small amount of turn from
pushrod at zero lash, can feel the pushrod
become resistant to twisting by hand and can't turn/twist it at all.
because of that slight turn of adjust nut i error on the
can't turn side.
since ref books call for 3/4 to 1 turn after this point
5/8's is a number i can live with.
so far, cough, no tappet noise using this value.
there is a small amount of turn from
pushrod at zero lash, can feel the pushrod
become resistant to twisting by hand and can't turn/twist it at all.
because of that slight turn of adjust nut i error on the
can't turn side.
since ref books call for 3/4 to 1 turn after this point
5/8's is a number i can live with.
so far, cough, no tappet noise using this value.
Last edited by calwldlife; Apr 10, 2018 at 01:52 PM. Reason: edit, 3/8 was wrong, i meant 5/8
Race Director
Joined: Apr 2003
Posts: 19,347
Likes: 654
From: Tampa, Florida
I've tried it both ways, running and not running. Maybe its my hearing but with the engine running there's so much clacking I cant really tell when it goes away. Last time around I did them with the engine not running.
Race Director
Joined: Apr 2009
Posts: 19,294
Likes: 2,753
From: Charlotte NC
With what is written above.ALSO....as written in the GM service manual...because we are dealing with a factory engine and no aftermarket performance parts.....The GM manual states that turning the rocker arm nut ONE full turn after zero lash puts the plunger in the lifter in the center of its travel.
And for what this is worth:
I also adjust the valves cold on a factory built engine...or an engine that was rebuilt to factory specifications using the instructions in the service manual and have NEVER had a problem at all doing it. But I have also verified that the notch on the harmonic balancer is in its correct position and the outer ring of the harmonic balance had not spun. And I have also adjusted valves while the engine is running using a valve cover that I modified so the oil does not spatter all over the place.
So many different ways to 'skin this cat'.
DUB
