I have my lower intake off so I'm studying how the lifter and springs work as I hand crank the engine. The lifter moves in two ways. The whole thing moves up and down and the center moves a tiny bit within that. Now when adjusting valves I am assuming it is the center part that you want to adjust half way. This is where I get confused. I adjust the valve just to zero lash no farther and then crank the engine by hand and the center looks as if it bottoms out. It wont go down any farther. So with one and a half turns past zero lash it gets to that point a lot faster. What I'm thinking is it isn't really bottomed out, it just has to much hydraulic pressure to go down any farther. The entire lifter will continue to push up but the center doesn't go down any farther. Would heavier duty springs be my solution to push back on the valve harder.
The lifter (the part that rides on the cam) has a piston in it with a little spring pushing up on it. There is a very small hole in the side that leads to the pressurized oil passage that oils the lifter. The oil pushes up on the piston to take the lash out of the valves. In the bottom of the little cup the push rods go in there is a little ball that plugs the hole you see in the cup. If you want to get the piston to go all the way to the bottom of the lifter you have to get the oil out of the bore of the lifter. Take a little wire and depress the ball while pushing down on the little cup, oil will come out the hole and the piston will go to the bottom. This is the piston you want about half way down the bore in the lifter. You can only adjust the rockers when the valves are closed and the lifter is all the way down. The spring in the lifter will hold the piston up, but not much pressure on it, so you have to take care you are not pushing it down. Take all the slack out the valve system and when it is just barely starting to push down the little cup, count the turns down on the valve adjustment, (avout 1 turn or so. Hope this makes a little sence to you. Larry
this is helpful. I know about adjusting valve lash, but every time I have done it I couldn't see the lifters. Now that I can see the lifters while adjusting it, it seems wrong. I would think it would go in further. From zero lash it would only take two full turns to go down as far as it does. I was expecting three+. What I would like to be able to do is see how many turns it takes top to bottom so that I have halfway exactly. So I should start by getting the oil out and then counting the turns. I have 1.6 rocker with arp studs that is why I'm trying to look into this. According to a mathematical solution that someone helped me out with in the past it ends up being about one and a half turns. Also If someone could chime in on the spring. How far can the spring compress before it is too far.
To see the pistons go clear to the bottom you need to let the oil out of them. You really don't need to do them all, the are all the same. They will slowly blead down by them selves, so I would just do a couple and see what happens. Larry
Keep in mind that the thread pitch on the ARP studs may be different than a stock stud - therefore, 1.5 turns may be too much.
Also - if you are truly at zero lash, the popet should not be "depressed" any. It does not take much to start moving the popet when trying to set zero lash. Especially if the lifters are partially deflated.
[This message has been edited by katatak (edited 09-15-2013).]
This is the formula that I was given awhile back to get the new turns past zero lash. Messing with it today however I did not get any of the lifters to travel more than two full turns so its seems as halfway is only one turn not one and a half.
If your rocker arms are a different ratio than stock, then you should correct for that also:
X = 1.5 x (Poem / Pnew) x ((Roem + 1) / (Rnew + 1))
X = New optimum number of turns of the adjusting nut past zero lash 1.5 = OEM specification (number of turns) Poem = OEM thread pitch (inches or mm) Pnew = new thread pitch (inches or mm) Roem = OEM rocker ratio Rnew = new rocker ratio
Edit: To correct formula term for rocker arm ratios
If there is oil in the lifters then you will not get them to travel full down. To get full travel on the little pistons you need to bleed them down by depressing the little ball in the bottom of the socket while pushing the piston in. Larry
One of the things I have witnessed is a lifter staying 'pumped up'. It freaked me out because you go to 0 lash, then 1.5 turns and the valve open partially because the lifter piston is hardened up...So I'm like, that can't be right looking at the rocker move.
It is though...
The better way is to drain the lifter oil as described above, then what should happen is find 0 lash, add the 1.5 and there should be some travel left in the lifter piston...it's a bit soft until it pumps up the first time it is run. Some argue .5 turns or 1.0 turns...doesn't really seem to matter as ling as you're in the travel of the lifter piston somewhere.