When the lifter is on the base circle, move the pushrod up and down while tightening rocker until slop just starts to go away?

Thanks,
Doug

 

Sounds good to me Doug, the manual says to add 1 turn to preload them after the slack is out, I usually just go 1/2 a turn.

 

That's it. Any manual will tell you how to static adjust hyd lifters. They usually state 1 turn past zero lash but I never go past 3/4 turn and mostly go 1/2 turn. At 1/2 turn I have never floated a lifter, even at 6200 rpm.

 

Stan M.

 

I like to rotate the pushrod back and forth with two fingers as well as the up and down motion. I feel like I get a better feel of zero lash.

 

1/2-turn down from zero lash has always worked fine for me.

 

If you plan on buzzing the engine past the limits, you are better off with less. In other words, once you exceed the limits of the valve springs from maintaining contact with the valve train components (valves, rockers, pushrods, lifter, cam) due to valve float, then the hydraulic lifters will take up that extra clearance it sees. This results in lifter pumpup and consequently poor engine operation for a little while, until the lifters bleed back down (valve are now off their seats even on the cam base circle).

The opposing view says more preload is better due to a longer time until any adjustment is required (more cam/lifter and valve train wear can occur until adjustment is required).

As John Z stated, 1/2 turn is a good "performance" starting point. But, sometimes only an 1/8 turn (or even zero) is good for throwing caution to the wind, and not being too careful on how high you rev it. Or 1 turn is OK for never having to touch them again. Your choice.

Just remember that one turn equals .042" (rocker studs are 24 threads per inch), and that is the amount the valve will be off the seat (and further into the combustion chamber) at full pump up.

Your choice

 

That is how I have always adjusted mine.

 

Note that hydraulic valve lifter preload has nothing to do with when a valve will float. That is strictly valve mass and speed, vs. spring pressure. The preload can be 2 turns or 1/8 turn and float will occur (for the same engine and components) at the same RPM. However, the net result will be very different, due to the greater amount of total pumpup with the 2 turns, as opposed to the 1/8 turn.

Plasticman

 

I'm surprised you are putting hydraulics in that monster small block ! Curious on the specs.
Pops

 

Plasticman, what do you mean by"the net result will be very different, due to the greater amount of total pumpup with the 2 turns, as opposed to the 1/8 turn."

What is actually happening to the valves at 2 turns vs a 1/2? I just intalled new valve springs. When I turned them 3/4 there was way to much noise as far as a clicking. When I went to 1 1/2 the noise stopped. Maybe I didn't do the lash the right way, not sure.

Lash challenged....

 

If you adjusted them correctly, there should of been no noise anywhere within the hydraulic lifter "range" of "automatic adjustment". That range is anywhere from a hair over zero turn preload, to over 2 turns. In other words, if the engine was up to temp, and you adjusted them while running, the lifters should of stopped making noise just as you hit the zero mark (all the valve train lash was then "taken up"). Then you continue tightening (slowly) the rocker adjustment nut to your predetermined setting (be it 1/8 turn, 1/2/ 3/4, or 1 full turn).

I normally set the hydraulic lifters with a stopped and cold engine while the intake is still off (if in the assembly process). That process is a lot "cleaner", but more involved, since each valve must be on the base circle for it to be adjusted (so rotating the engine by hand is necessary). But by feeling the resistance to turning of the pushrod (as I tighten the rocker adjustment nut), I can tell when I have hit the zero preload mark. If the intake is off, I can double check myself by seeing the lifter plunger depress as I hit zero preload.

As to your question: What is actually happening to the valves at 2 turns vs a 1/2?

I was referring to how far the valve would intrude into the combustion chamber if the valves floated. Once they float, the lifters will take up that float clearance (lifter pumpup). At 1/8 turn adjustment, the valve would only protrude .005". Not much, and the engine would recover from this very quickly.

At a 2 turn adjustment setting, the valve would protrude .084" where it would have a much greater chance of contacting a piston coming up (remember, it is now raised off the valve seat by that higher amount during all piston movement, so even on the cam base circle, the valve is sitting .084" off the seat). Also the larger clearance would cause the engine to run terrible (if at all) and the lifter would take a lot, lot longer to bleed back down.

At 1/2 turn, the valve would have the potential of protruding .021" into the combustion chamber after a valve float. Far less than at 2 turns. But not as good as with 1/8th turn (.005").

Hope this helps,
Plasticman

 

Definitely go looser than spec. I think one of the How To (Build? Hot Rod?) Small Block Chevy books said turn it down 1/4 turn past when the lifter quiets, then back open 1/16. Thus 3/16 down from quiet, always worked well for me.

You don't want to squeeze the cam too tight. Each of my C2s that were adjusted as described went faster and got better mileage than at stock tightness.

 

Plasticman, thanks this is great info.

I have roller rockers, with the valves adjusted cold, should you be able to wiggle the roller arms a little left and right, or are they tight, with no movement? My guess is too tight and the valve will not close all the way.

This is great timing becasue I am going back out to work on them.

 

Sub,

It does not matter if down 2 turns or only 1/8th turn as far as the cam/lifter "tightness" on a hydraulic cammed engine. The "tightness" does not vary at all within this range. It is determined by the oil pressure and viscosity that is pumped into the hydraulic lifter, and the clearances within the lifter (more internal lifter clearance, more leakage).

In other words, the cam "action" and subsquently engine torque/power will not change if the hydraulic lifter preload is 1/8th turn or 2 turns. All you are doing is centering (or offsetting) the plunger within the lifter. 3/4 to 1 turn is normally considered the center position. Anywhere up or down is offset from center.

Now a thicker oil will allow the lifter to bleed down slower, and therefore the lifter would collapse less under high spring pressure, so a tad more lift would be seen. But, higher viscosity oil will cause more engine drag, so you gain some, you lose some.

Plasticman

 

Moving the rockers side to side really will not tell you if they are adjusted correctly.

If checking cold/off, I would use the pushrod feel test to determine when the pushrods (and therefore the lifters) are at zero preload. With the rocker lose, and as you slowly tighten the rocker adjustment nut, roll the pushrod with 2 fingers. As you hit zero, you will feel a resistance to the pushrod to turning. That is "zero" preload.

But you MUST make sure each valve is on the cam base circle when doing that. The best way I know is the Crower method. Take the firing order (18436572 for a small block Chevy). Put the first 4 numbers over the 2nd 4.

1843
6572

The top and bottom in each vertical col. are a pair and fire 360 degrees from each other. #1 fires when #6 is on the exhaust stroke, and vise versa. #4 and #7, etc. are all pairs. This means that when #1 intake valve is on the exhaust stroke, #6 intake is on the compression/firing stroke and can be adjusted. If #1 intake is fully open (easily seen with valve cover off), then you can adjust #6 intake. Same holds true for any valve. Example: Note when #3 exhaust is at full lift, and adjust # 2 exhaust.

Either that, or adjust each valve (one at a time to note when the noise stops) when the engine is hot and running.

Plasticman

 

I am going to zero lash the hydraulics, with this cam, those are good for about 7500 RPM.

I was looking to verify initial lash setup so I can put maybe 30 miles on it, then go back in, loosen each to clatter, tighten to just not clatter, then about 1/16- 1/8 turn past no clatter.

Thanks,
Doug

 

Doug,

Sounds like a great plan. You probably will see a little wear (normal wear in / seating) during that first 30 miles, so they may start clattering all by themselves if adjusted at zero to begin with. But by readjusting, you can tell how much wear you are seeing.

Plasticman

 

Plasticman, again thank you for sharing your knowledge.

Just trying to understand. Isn't the same thing accomplished by doing one valve at at time by having the intake open and adjust that exhaust, then open that exhaust and then adjust that intake?

 

That can be debated (and has been). Problem is overlap of cam, and extremely long clearance ramps of OEM Chevy cams cannot guarantee that the cam is on the base circle. Only positive way I know is the method I described (from Crower). That ensures that the cam has to be smack in the center of the base circle, since the opposing cylinder/ and fully opened valve is 360 degrees away.

Not to say that other methods don't work, just know for sure that what I am saying does work.

Plasticman