SETTING TIMING AND ADJUSTING VALVES

juskol18

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Apr 14, 2015
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I just finished having the heads resurfaced and the valves reseated. I have the heads and the intake on, now I just need detailed instructions on how to set the valves and the timing. I had found the valve procedure once, Now I can't find it anywhere. The motor is a mercruiser 5.7 pre-vortec with 12 bolt intake.
 

Bt Doctur

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Aug 29, 2004
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easiest way it to get the intake valve to open and close, this put the cylinder on its compression stroke , tighten until the pushrod just stops spinning, and go 3/4 more.
When all the valves are adjusted, get #1 cylinder intake to open and close. slowly turn crankshaft until the 0 mark is on the pointer, install dist with rotor pointing to #1 in the cap.
 

sub2010ss

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Feb 17, 2015
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Yes, what he said. You can tell the rocker is touching the pushrod by slowly spinning the pushrod between your fingers, when there is drag, its touching. Also, when you drop in the distributor, you will have to be pointed slightly counterclockwise from the number one wire, that way as is drops in and engages the gear it will rotate into position and point directly at number one. This took a few attempts when I did it last. Also, you will have to ensure the oil pump is aligned with the distributor or the distributor will not drop all the way down. You can do this by using a large, long flat bladed screw driver and align it in the same direction as the distributor slot.
 

flipbro

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Feb 8, 2013
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Here's how I adjust valves. #1 tdc on compression stroke both valves will b e closed. Adjust your #1 ex #1in 3ex 5in 7in 2in 4ex 8ex.. Now rotate the crank 360degrees and adjust #3in 5ex 7ex 2ex 4in 6ex 6in 8in. Zero lash is determined by slowly turning the pushrod as you tighten the rocker nut as soon as you feel drag on the push rod you have zero lash now tighten the nut half to three quarters turn and that valve is done. When you stab in the distributor make sure your on #1 compression tdc. Have fun and good luck
 

achris

More fish than mountain goat
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Interesting. All my Merc service manuals call for an additional 1 turn after zero lash.... Where are you guys (BT and flip) getting this 3/4 from?
 

Fishermark

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In addition to the above, I will note that it is very easy to overtighten your adjustment. Getting zero lash is more a "feel" and art than a science! In other words, it is very easy to miss the point at which all the lash is taken up. You certainly don't want to tighten till you cannot turn the push rod with your fingers. As you are tightening the rocker, gently spin and lift the push rod up and down - you can tell you have reached zero lash when you no longer have any up and down play.
 

flipbro

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Chris thats just the way I was shown and has always served me well with no issues..You must be sure your hydrolic lifters are good and stay pumped up to preform this procedure. .
 

sub2010ss

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Chris thats just the way I was shown and has always served me well with no issues..You must be sure your hydrolic lifters are good and stay pumped up to preform this procedure. .

Interesting about the lifters being pumped up. This statements makes me think you would have to prime that engine prior to adjustment, which I don't believe to be true. Am I wrong on this? If so I need to get in and adjust my rockers!
 

Bondo

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In addition to the above, I will note that it is very easy to overtighten your adjustment. Getting zero lash is more a "feel" and art than a science! In other words, it is very easy to miss the point at which all the lash is taken up. You certainly don't want to tighten till you cannot turn the push rod with your fingers. As you are tightening the rocker, gently spin and lift the push rod up and down - you can tell you have reached zero lash when you no longer have any up and down play.

Ayuh,.... That's what I Hate 'bout the shop manual explanations,....

It Ain't the Spin, it's the free movement, 'tween the lifter, 'n rocker,.... Lash,....

I do more pullin', 'n pushin',.. Gently,... than any spinnin' the pushrod,...

'n as for pumped up lifters or not,....
The seat is in the same place, held by the spring,...
There's just atad more resistance to compression full of oil, vs. not havin' ever been run,...

I've lost track of how many posters have shown up here with a new reman that won't start,....
Ya finally get 'em to do a compression test, 'n there ain't any,.... Valves Toooo tight,...

I was always taught that 3/4 to a turn puts the lifter piston in 'bout the middle of it's stroke,...
It's a Hyd. lifter,...... it ain't that Critical a measurement,......

Critical is on a solid lifter motor, ya set lash with feeler gauges,...
 

Scott Danforth

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ooooh, a rocker arm lash thread.....

just bustin' everyones chops. Been doing it the way Bondo pointed out since I was knee high to a spark-plug myself, and on every brand of engine with adjustable rocker arms.

its a wiggle/giggle vs spinning.
 

Tail_Gunner

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ooooh, a rocker arm lash thread.....

just bustin' everyones chops. Been doing it the way Bondo pointed out since I was knee high to a spark-plug myself, and on every brand of engine with adjustable rocker arms.

its a wiggle/giggle vs spinning.

Calm down pops its spin to win and jiggle for giggles. Jezzzz some peoples kids.
 
Last edited:

NHGuy

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May 21, 2009
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Yup, and some companies say to only go half a turn past zero lash. That's what I was told and did with my new Comp cam & lifter package last spring.
 

Silvertip

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And it has been 3/4 - 1 turn down since the small block appeared in the fall of 1954.
 

achris

More fish than mountain goat
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And it has been 3/4 - 1 turn down since the small block appeared in the fall of 1954.

So, is it 3/4 or 1?

From my understanding, it's more to do with rocker ratio, cam lift, lifter stroke. Nothing to do with the block. In Mercruisers, 'Standard' lifters with a standard cam should be set 1 turn down from zero lash, not 3/4, not ABOUT 3/4, not 1/2, 1.... Check in every Mercruiser manual, 1 turn....
 

Bondo

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So, is it 3/4 or 1?

From my understanding, it's more to do with rocker ratio, cam lift, lifter stroke. Nothing to do with the block. In Mercruisers, 'Standard' lifters with a standard cam should be set 1 turn down from zero lash, not 3/4, not ABOUT 3/4, not 1/2, 1.... Check in every Mercruiser manual, 1 turn....

Ayuh,..... I believe it's got to do with havin' the lifter's plunger in or about centered in it's length of stroke,....

I agree with Silvertip,.... I've been taught, since I 1st picked up a 9/16" wrench, that they're set to 3/4er's to 1 turn, after zero lash,.....

As I said above, it ain't a critical measurement,....
 

Fishermark

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Ayuh,..... I believe it's got to do with havin' the lifter's plunger in or about centered in it's length of stroke,....

I agree with Silvertip,.... I've been taught, since I 1st picked up a 9/16" wrench, that they're set to 3/4er's to 1 turn, after zero lash,.....

As I said above, it ain't a critical measurement,....

That's exactly right. The beauty of a hydraulic lifter is that it has a wide built in "span" of adjustment that allows them to operate correctly. It does not need to be exact. Somewhere between 3/4 and 1 turn is good.
 

nateo

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so should the pushrods still spin freely? When I did mine I think I stoped right before they stopped spinning and not necessarily as soon as I felt resistance. Then I went 3/4 turns. Now boat not running good. Perhaps I tightened too much?
 

NHGuy

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May 21, 2009
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I read your other posts, wouldn't hurt a bit to revisit the adjustment.
There's zero lash when there's not vertical movement. But you just stated that you were thinking you were at zero lash when the pushrods stopped spinning. That's a little too late. So you could have too much adjustment which would not let the valves be tightly closed.
 
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