Hydraulic Lifter Preload Trouble on 68 289

[Phillyfanfrombirth]

Some highly respected guys on here suggested an easy way to do it would be too simply put the exhaust lifter all the way down, then adjust the intake. Now put the intake all the way down, and do the exhaust. Do this working your way thru the whole system.

Absolutely... This makes it visibly easy to know which valve should be completely seated.

If I understand correctly, what you are saying is that the lifter will pump up once the engine is started. That means that the lifter height at rest isn't the lifter height with oil pressure. In that case, yes, it does seem to be an iterative process. That explains why I hear much less valve noise after doing the last round of adjustments. Sounds like its time to do this a few more times.

When I was first getting into engines when I was a teenager, I didn't have anyone show me or explain this to me. So, I would tighten the rockers as you are saying... then come out the next morning and recheck my work. They were all loose again and I had no idea why. I would then start the engine and it would run like crap... Then, I would take the valve covers back off only to find that EVERYTHING was incredibly tight.

So I'd back it off again and start over... I played that game for quite a while before getting it right.

As far as the lifter height... it is the same at rest, but ONLY if it is allowed to be. By having too much preload, you don't allow the lifter to expand 100% as the pushrod is acting to restrict it. Then when it rests, the pressure put on the lifter forces some of the hydraulic pressure out... This is what I found the hard way when I adjusted the valves at night, only to find that they were loose again in the morning, the hydraulic pressure was bled out overnight. The same would also be true for the valves that are open, which is why I advocate starting and stopping the engine just before you do all of this. The longer it sits, the more pressure will bleed from the lifter.

But that begs the question: How do I know what my preload is if the lifter height changes with oil pressure?

That's why the process needs to be started with as little pressure as possible on the lifter. When the motor starts, the hydraulic pressure will solidify the lifter. To stop the ability of the pushrod to spin, you have to have a load on it. Think how much pressure would have to be on something round that you would no longer be able to spin it... that ability doesn't go away until there is a measurable pressure exerted on it. When I get to that point, I stop and will even back it off until the point where it does spin with some effort.

With that little bit of "spin"left in the pushrod, you can check your work by starting up the engine, stopping it, and then checking to make sure that each pushrod can still be spun when its valve is seated. If not, that means that the hydraulic pressure built up on the lifter so that the lifter has increased the preload... so you have to back that nut off until it spins again, and recheck.

It's going to take a while... so don't rush it, but the satisfaction of having it done right (and not having to go through it again) will be worth it. I usually end up going through the process at least 3 times... the last time to double check.