Hydraulic Lifter Preload Trouble on 68 289
 

I've gone through the process of setting the lifter preload on my 68 289 a couple of times as I hear some valve tap. Every time after going through the procedure, the engine runs rough and I end up backing off on the preload. The engine smooths out once the lifters get back to zero preload for some reason. I've tried 1/8, 1/4, 1/2 and 3/4 turn preload settings, all with the same result. It barely ran at the 3/4 turn setting. I determined #1 cylinder TDC by the rotor position, and found the pushrods with no preload so its likely I'm in the right position.

Could there be a problem with the lifters themselves?
Could this be a valve issue?

Any help would be appreciated.

Re: Hydraulic Lifter Preload Trouble on 68 289
 

I'd run the engine, pull the valve covers off, grab a pushrod on a valve that is seated between your index or middle finger and your thumb, and have a socket on the nut...

If you can't spin the pushrod with your fingers while the valve is seated, back off the nut...

If you can spin the pushrod relatively easy with your fingers, then slowly tighten as you keep spinning the pushrod. When you can no longer spin the pushrod, back off nut until you can.

Go through the engine progression until you have them all adjusted. If there were any pushrods that wouldn't turn, loosen them until they do spin and note their position... put the valve cover back on, and start the engine long enough to get oil pressure back. Go back and check that all pushrods are on the same brink of being able to turn them.

This may take 2 or 3 tries to get them all at the same level. If they are already tightened too far, the lifters will have the hydraulic pressure removed from them, giving you the false impression that they need tightened. When you start the engine back up, the hydraulic lifters will solidify and give you an accurate gauge of where you are.

You may even wish to back off all of the rocker arm nuts until they are noticeably loose (not so loose that they will fall off, but loose enough that there is some play)... replace the valve cover and start it just to start from scratch and so that you know that nothing is already too tight.

Re: Hydraulic Lifter Preload Trouble on 68 289
 

Are the cam and lifter new?? Are the valves new??

If you're adjusting them, Phillyfanfrombirth has the correct answer. I've personally ne ver had a problem adjusting any of them, including Ch**y's.

Back off or tighten down till it spins and tighten in 1/3-1/2 turns and lock it down. If ater a couple of time adjusting and you're still getting valve clatter, check the oil pressure and if it is OK replace the lifter.

Re: Hydraulic Lifter Preload Trouble on 68 289
 

I'd wouldnt use the rotor for #1, use the balancer and timing pointer.

Re: Hydraulic Lifter Preload Trouble on 68 289
 

By what Phillyfanfrombirth is describing, it seems as though this would get the lifters to zero clearance but no preload, correct? From all of the hydraulic lifter adjustment procedures I've read, the next step would be to add 1/2 to 3/4 turn on the rocker nut to put the lifter somewhere in the middle of its adjustment range. (This also applies to both cold and hot engines, so it seems non-critical.) Yet, when doing this, the engine runs very rough.

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.

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

I don't mean to make this overly complicated. Just trying to get a good understanding of the process. By the way, Gearhead, the motor was rebuilt many years ago, and has about 15K miles on the build. (C-code 289, totally stock.) The valves and seats were re-ground and springs shimmed. She runs strong, just trying to work out a few kinks. Starting with the valves, then moving to carburetion next.

Thanks for all your help guys.

Re: Hydraulic Lifter Preload Trouble on 68 289
 

I just dealt with this problem a few weeks ago. I have never had troubles adjusting the valves, until this last recent attempt. I tried going thru the firing order, with no such luck.

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. When I got the pushrods to zero lash, I went 3/4 of a turn this time. I usually only go ½ turn, but was tired of messing with the car at that point and wanted to get it done the first time. This worked perfectly and the valve train is silent once again.

This is all assuming you have stud mounted rockers.

Ryan

Re: Hydraulic Lifter Preload Trouble on 68 289
 

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

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.

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.

Re: Hydraulic Lifter Preload Trouble on 68 289
 

Are you certain that you have hydraulic lifters? If you do have mechanical lifters any preload at all would leave the valves open when they should be closed and cause the engine to barely run.

The preload on the hydraulic lifter settings is just caused by pushing the push rod slightly down against a small spring in the lifter. After the engine starts up the oil pressure keeps the lifters pumped up to the proper level for a zero valve lash adjustment. The only advantage to the hydraulic lifter is that the "hydraulic adjustment" is automatic so you don't need to adjust very often.

Once you do adjust with the afore mentioned prerload (1/4-3/4 turn when the lifter is on the base circle of the cam), you should not need to do it again and again.

Try it as Ryan suggested. Also make sure you do actually have a hydraulic lifter cam.

Rev

Re: Hydraulic Lifter Preload Trouble on 68 289
 

Guys,

Many thanks for saving me the grief of learning this the hard way. I see now why you recommend to loosen the nuts a bit, run the motor to get oil pressure back, then start the adjustment process to find zero lash. Sounds like it will take a couple hours to go through the process properly. Need to make sure the wife doesn't have a long honeydo list first....

Just to be sure:
The above procedure is just to get to the zero lash condition. Once this is established with reasonable certainty, I assume everything gets adjusted an additional 1/2 to 3/4 turn tighter to put the lifters somewhere within their adjustment range. If so, this would agree with rwhite's comments.

@Rev: The lifters are absolutely hydraulic. Stuffed them in there myself way too many years ago.

@rwhite: Yup, stud mounted rockers. And yes, I'm tired of messing with the car and want to spend more time actually driving the thing. Thanks for the rocker position tip - sounds foolproof.

Re: Hydraulic Lifter Preload Trouble on 68 289
 

I honestly don't tighten the rocker arm past the point where the pushrod doesn't spin... there is already significant pressure on the pushrod if you can't spin it with your fingers.