C2 327 hydraulic lifters bleeding down

[William G.]

Re: C2 327 hydraulic lifters bleeding down

Tim, yes I was careful to take the slack out of the pushrod but not tighten too much. I used some .002 steel shim stock between the rocker arm and spring to tell me when the I was approaching zero lash. I'm going to turn the motor manually without starting the engine and notice which ones are not pumped up. Then I will change oil and filter, let it warm up to distribute new oil, followed by adjustment while running.

[Timothy B.]

Re: C2 327 hydraulic lifters bleeding down

William,
If you turn the engine over and find loose rockers then I would adjust every valve again. This can be done cold by the #1 TDC #6 TDC method described in the service manual and I would not use .002 stock. Just turn the nut until the feel of the push rod snugs and then one complete turn additional. The .002 stock may be where you are getting in trouble. As I suggested before 17" vacuum is high for L79, they are usually 14"+- but this may be the case if there is play in the valve train because there is less valve overlap.

[Duke W.]

Re: C2 327 hydraulic lifters bleeding down

Make absolutely certain that you are adjusting the correct valves at #1 and #6 TDC IAW the service manual. This is easly to screw up for the novice. Make sure you understand the cylinder numbering scheme/valve layout on each bank. Check whether each valve lines up with an inlet or exhaust manifold runner to be sure you are working on a correct valve for the crank index point. Draw a diagram.

Lossen the rocker nut until there is clearance, then wiggle the pushrod up and down its length while slowly tightening the nut until the play is gone - then 3/4 turn. This does not have to be a "precision adjustment" - just in the ballpark.

Forget about the feeler gage - .002" is noise level. The point is to get the plunger about halfway down its travel. Various sources suggest 1/4 to 1 turn prelaod, and 1 turn will yield about .072" preload. The more preload you use, the more allowance there is for normal wear, and 1/2-3/4 turn is usually good for the life of the engine.

As part of this job, check rocker nut preload with a torque wrench. I know of no specification, but I would replace any that are less than 10 lb-ft or remove any that are less than 10 lb-ft and peen them until they have at least 10 lb-ft breakaway torque.

Duke

[William G.]

Re: C2 327 hydraulic lifters bleeding down

Again, to all who have posted to try to help me solve my lifter problem, thanks! Duke, I am very much aware of the cylinder locations and the difference between each intake and exhaust valve. So that's not the problem, although I am sure I can make a mistake here and there.But I was painfully careful to check and double check my adjustments.

Today I did a static cold adjustment by the book. I used 3/4 turn preload. Same thing happemed when I started the engine...two or three lifters clacked for 10 seconds and then the noise subsided and the engine ran smoothly. I did notice during adjustment that three nuts required noticeably lower torque while tightening the 3/4 turn preload and I recorded their locations. I will definitely buy a new set and install. However I did not see any evidence that they had loosened to cause the problem. The original 3/4 turn preload had not changed.If the nuts were loosening it seems to me that eventually they would not pump up at all and the clacking would never go away. I have not been able to locate which ones are making the noise.
I warmed up the block to operating temperature and drained the oil and replaced oil and filter, then ran the engine at 2500 rpm for a while to hopefully clear out any contamination suggested by Crane Cams. I will know in the morning if that worked. More later!!!

[Michael H.]

Re: C2 327 hydraulic lifters bleeding down

Again, to all who have posted to try to help me solve my lifter problem, thanks! Duke, I am very much aware of the cylinder locations and the difference between each intake and exhaust valve. So that's not the problem, although I am sure I can make a mistake here and there.But I was painfully careful to check and double check my adjustments.

Today I did a static cold adjustment by the book. I used 3/4 turn preload. Same thing happemed when I started the engine...two or three lifters clacked for 10 seconds and then the noise subsided and the engine ran smoothly. I did notice during adjustment that three nuts required noticeably lower torque while tightening the 3/4 turn preload and I recorded their locations. I will definitely buy a new set and install. However I did not see any evidence that they had loosened to cause the problem. The original 3/4 turn preload had not changed.If the nuts were loosening it seems to me that eventually they would not pump up at all and the clacking would never go away. I have not been able to locate which ones are making the noise.
I warmed up the block to operating temperature and drained the oil and replaced oil and filter, then ran the engine at 2500 rpm for a while to hopefully clear out any contamination suggested by Crane Cams. I will know in the morning if that worked. More later!!!

You have a lifter bleed down issue. If the clicking goes away after a few minutes of running, that means the lifter refilled and the adjustment is correct, or at least somewhere near correct.
Hydraulic lifters do bleed down after an engine is shut down but it normally takes a longer amount of time. On startup, during cranking, the moment the lifter is on the base circle of the cam with zero valve spring pressure holding the lifter plunger down and seating the check ball, it automatically refills itself, or "pumps back up".
If you have "anti pump up lifters", the refill process is slowed down considerably. That's what makes it an anti pump up lifter. The refill rate is slow so you can float the valves for a brief instant without lifter pump up.

It's not necessary to lash valves at zero with anti pump up lifters.

If there's a small particle of dirt or a poor seat at the lifter internal check ball/seat, the lifter plunger will leak slightly, allowing the valve spring pressure to force oil out of the lifter. You can often see this occur just after you shut the engine down. One or more open valves will begin to slowly close as the oil bleeds off.

One more item that may cause this problem is aftermarket valve springs that are too aggressive as far as spring tension.

I agree with others on the use of EOS. I believe this would increase the viscosity of oil, not decrease it.

Good luck with the project.

[Clem Z.]

Re: C2 327 hydraulic lifters bleeding down

i have never seen a anti pump up lifter that did not need to be "zero" lashed,turns it into a solid lifter,to prevent pump up but maybe there is something new out there. the lifter is bleeding down so if it is the same lifters i would take it apart and make sure there is no debris inside causing the check ball not to seal

[Michael H.]

Re: C2 327 hydraulic lifters bleeding down

i have never seen a anti pump up lifter that did not need to be "zero" lashed,

If any stock lifter is zero lashed, it automatically becomes an anti pump up llifter because it's already pumped up as far as it can go.

True anti pump up lifters have a very small feed orifice which slows down the fill process. The valves can float for a few seconds but the slow fill lifter doesn't compensate for the lash immediately like a stock lifter.

The only time any lifter over fills is when the valves are floated slightly and the internal check ball is no longer under pressure.

[Clem Z.]

Re: C2 327 hydraulic lifters bleeding down

If any stock lifter is zero lashed, it automatically becomes an anti pump up llifter because it's already pumped up as far as it can go.

True anti pump up lifters have a very small feed orifice which slows down the fill process. The valves can float for a few seconds but the slow fill lifter doesn't compensate for the lash immediately like a stock lifter.

The only time any lifter over fills is when the valves are floated slightly and the internal check ball is no longer under pressure.

the instruction for F/M(SPEED PRO) "HI REV" hyd lifters tells you to "zero" lash. maybe crane has something new.

[Michael H.]

Re: C2 327 hydraulic lifters bleeding down

the instruction for F/M(SPEED PRO) "HI REV" hyd lifters tells you to "zero" lash. maybe crane has something new.

The original anti pump up lifters from the old days used this "slow fill" system and I would assume that it continued to this day.
If you zero lash, there's no need for anti pump up lifters because they can't pump up any further.
That's the whole principal behing the hydraulic lifter to begin with. It's designed to quickly take up any lash in the valve train as soon as there's no load on it, as would be the case when the valve is closed. (or floating)
as soon as valves float, even slightly, and the pressure is off the inner body, the check ball is unseated and oil is allowed in to fill the lifter further. That's what pumped up is. It's over full and now the valve is held open, even when the lifter is back on the base circle of the cam lobe.
It usually takes several seconds for the excess oil to bleed off and the valve to return to the seat.

When an engine with hyd lifters is running and you back off one of the rocker arm nuts, that valve/rocker suddenly starts to clack for a few seconds but then it stops clacking. That's because it takes a few seconds for oil to enter the lifter and fill the new void created by the adjustment. If there's no pressure on the lifter when on the base circle, it automatically fills.

That's exactly the same thing that occurs when the valves are floated. The lifter is trying to fill the new gap in the valve train.

Zero lashing anti pump up lifters is only an extra margin of security.

[Joe R.]

Re: C2 327 hydraulic lifters bleeding down

You have a lifter bleed down issue. If the clicking goes away after a few minutes of running, that means the lifter refilled and the adjustment is correct, or at least somewhere near correct.
Hydraulic lifters do bleed down after an engine is shut down but it normally takes a longer amount of time. On startup, during cranking, the moment the lifter is on the base circle of the cam with zero valve spring pressure holding the lifter plunger down and seating the check ball, it automatically refills itself, or "pumps back up".
If you have "anti pump up lifters", the refill process is slowed down considerably. That's what makes it an anti pump up lifter. The refill rate is slow so you can float the valves for a brief instant without lifter pump up.

It's not necessary to lash valves at zero with anti pump up lifters.

If there's a small particle of dirt or a poor seat at the lifter internal check ball/seat, the lifter plunger will leak slightly, allowing the valve spring pressure to force oil out of the lifter. You can often see this occur just after you shut the engine down. One or more open valves will begin to slowly close as the oil bleeds off.

One more item that may cause this problem is aftermarket valve springs that are too aggressive as far as spring tension.

Mike, I think you have raised some interesting points. I agree that the evidence points to a leakdown issue, not a lash issue.

I always thought that anti-pump-up lifters had a faster leakdown rate than standard lifters. If they have this *and* a slower fill, possibly aggravated by excessive pressure aftermarket springs, it seems possible that the problem could be characteristic of the lifter/spring combination.

If so, it may be that the specific lifters that are draining down are whatever lifters were holding valves open when the engine stopped. In other words, it may not be the same lifters each time.

Offhand I can't think of a way to determine whether it is the same lifters each time or a different group. Perhaps after the engine has sat overnight, it could be turned over by hand to locate loose rockers when the associated valve is closed. Then run the engine briefly and repeat the loose rocker test the next day. If it is a different set of rockers the next time, it would point clearly toward a system problem with the lifter/spring combination.

[William G.]

Re: C2 327 hydraulic lifters bleeding down

Joe, the springs are definitely a possiblity to look at. I have made a little progress in the last few days as follows: I made a valve cover with holes and readjusted the preloads which were just about the same as when adjusted statically. I am sure my problem is not one of incorrect preload. I changed the oil and filter and ran the engine a bit . This morning the bleed down is all but gone. Only one or two ticked for a second or two. Unfortunately I have not had the opportunity to run the car on the street because I just received the hood, headlight buckets and decklid from the painter. I want to work the engine at a higher rpm for a while and then change the oil again. If that doesn't work, I'll look at the springs. But so far, I think I might have had some contamination. Thanks to all of you for your input.

[Ted K.]

Re: C2 327 hydraulic lifters bleeding down

Too high tech. How about the old shadetree mechanic way. Warm up the engine, remove the valve covers, back off the adjustment nut until it clacks and tighten 1/4 of a turn at a time until you have completed one full turn.
Or for techies, since engine was a recent rebuild could a cam bearing not have been properly inserted affecting the oil pressure?