Hydraulic Lifters

Maxwedge...(or anyone else who knows)

My engine is a 3300 series from 1991. I have 280,000 on the clock. This is an engine that runs very well, is well kept, and compression tests at a rather tired 95 to 115 max across all 6 cylinders. It's normal wear. It does not knock clunck or tick. It doesn't misfire or idle rough... its nice.
My question is regarding various fixes for low compression, and the possible link to low compression due to ineffective hydraulic lifters.

1. How long can hydrualic lifters hold up before they loose efficiency, (compared to piston rings/valve seats/valves) and besides ticking, what are the symptoms?

2. Is uniform low-compression indicitive of worn rings/cylinder walls, or could it also be valve train related...i.e lifters (excluding burned/worn valves).
This question should be clarified... I know worn cylinder walls and piston rings are a given, but would replacing lifters (easier than pulling whole engine) increase my compression marginally by increasing valvetrain performance assuming valves were in decent shape and sealing well?

I hope this was clear enough. Thanks.

If the lifters are really weak and worn this Could make compresion low but its more likly the rings/piston or valves/valve springs.

Reason would be that if they are weak then they are not fully opening the valves.
So your vavle springs are what keeps them closed .
If they dont close fully, then it would have low comprs.

Do you have low oil pressure also ?
When doing your compresion test did you do it dry,
or with a few drops of oil in the cylinders?

If the lifters are really weak and worn this Could make compresion low but its more likly the rings/piston or valves/valve springs.

Reason would be that if they are weak then they are not fully opening the valves.
So your vavle springs are what keeps them closed .
If they dont close fully, then it would have low comprs.

Do you have low oil pressure also ?
When doing your compresion test did you do it dry,
or with a few drops of oil in the cylinders?
my boss let me do some work on my car in the shop... so i didnt abuse the priviledge by taking to long. I had some wiring and things to do, and changed the plugs and wires with nice ac delco stuff... I compression tested dry. I would have loved to take the time to add a little oil in the cylinders to see if that would have boosted compression a little, but didnt.
as far as oil pressure is concerned... its great, in fact, i'd be inclined to think maybe the pressure relife is a little jammed, because at idle operating temp I run 50 psi for oil pressure.
thing is my haynes manuals listing for oil pressure says minimum 35 psi @ 2000 rpm... that seems kinds messed up though, but haynes isnt always accurate anyway.
I need to do a cylinder leak-down test in the future to determine valve train health... I did find out something about lifters that didnt occur to me. Since they are hydraulic, they adjust to compensate for valve stem or pushrod wear...(i believe)...
This begs another questions, which is... in a scenario where an engines lubricant is often replaced before needed, and the engine is driven moderately, how long milage wise before the lifters can no longer adjust to compensate for wear?? I have 281,500 kilometers (175,625 miles) on this motor.

You would have to have catastrophic wear for the lifters to run out of adjustment area. A leak down test is the best way to check for ring seal and valve seal but it will not tell you the condition of the oil rings. The lifters are not really an issue in a well maintained engine, when you did the comp test did you hold the throttle open this can skew your readings.

You would have to have catastrophic wear for the lifters to run out of adjustment area. A leak down test is the best way to check for ring seal and valve seal but it will not tell you the condition of the oil rings. The lifters are not really an issue in a well maintained engine, when you did the comp test did you hold the throttle open this can skew your readings.

I did not hold the throttle open... you have my interest now, please explain why this can skew the reading and how...im thinking about the relationship now between an open throttle plate and cylinder pressures... nothing obvious coming to mind.

Well stop and think here ,how do the cylinders fill with air if the throttle is closed?

They won't fill completely if the throttle isnt wide open.
i would put a large object on the gas pedal and remove the ECM fuse

Well stop and think here ,how do the cylinders fill with air if the throttle is closed?

The same way as when i start the car any other time... (laughing) Now that you have educated me though... I can see how the idea works... thanks very much for the knowledge!!!

The same way as when i start the car any other time... (laughing) Now that you have educated me though... I can see how the idea works... thanks very much for the knowledge!!!

one more thing... seeing as you know of this... have you seen this mistake made and noticed the difference when the test is properly performed? By how much could you expect pressures to rise?

Could be in the 10-30 psi range, cranking rpms is also critical, 3 revolutions or 3 compression strokes is where the readings should be recorded.

Could be in the 10-30 psi range, cranking rpms is also critical, 3 revolutions or 3 compression strokes is where the readings should be recorded.

Awsome... something to think about! Merry christmas MaxWedge!

If you have taken good care of your car and changed that oil at the recomended intervals,
then the lifters should last for a very long time.

IF they get gummy or a build up on them they can stick causing that anouying tickticktick..

Merry Xmas everyone!