voda1

All though the part number is the same 17122490 and was used in 2003, why is the LS7 lifter first used in 2006 given so much more notoriety?

PREDATOR-Z is saying that the info provided is not for the LS7 lifter. I'm just trying to figure out why.

Eric D

The table listed above was put together showing ALL units used in LSx engines. If someone is claiming there is something else have them supply you the part number and we will compare.

cdkcorvette7

Cool thread

murf257

I know I speak for others, but we appreciate the time and effort you and others take to spread your knowledge and experience. There are many like me who enjoy mechin' but lack the knowledge.

With that stated, I was impressed in the more finished looking product minus the mechanical blems!

red-in-la

Curious question... If you are getting a knock when starting in the morning what part of the lifter has the oil drained out of? And why? Thanks

Eric D

How confident are you that the noise is lifter? Piston slap noise to some can be mistaken as valvetrain related. During a cold start, if you rev the engine to about 1600 to 1700 rpm, piston slap increases in noise level. It will reduce as the engine warms.

red-in-la

Fairly confident. I spent 10 years in the Miata community and this was a very common sound. I also tried your 1600 rpm test and the noise actually decreased to disappeared.

So I'm still interested in where the oil goes to "pump" the lifters up and how they work and why they have oil in them since they also have springs in them. Never thought about this stuff and got curious.

Thanks....
p.s. my Miata was Yellow

Eric D

Red,

How the hydraulic lifter works isn’t complex in principle. On the side of the body is the oil passage and oiling hole. (See picture below) The oil hole allows the oil into the low pressure chamber. This chamber holds the oil that feed up to the pushrod through a metering plate. At the lower end of the low pressure chamber is the feed to the high pressure chamber past the one way check ball. Any play in the valvetrain stack-up will be taken up by the check ball coming off its seat allowing oil to flow past it and into the high pressure chamber.

Eric D

What Causes a Lifter to Make Noise

There are a number of issues that can cause a lifter to become noisy on startup, or even all the time. Here are some of the more common ones and I’ll go into more detail later in this write-up;
Before going into details of the causes listed above, an understanding of the reason why we use hydraulic lifters would be helpful.

Why do we use hydraulic lifters? Couldn’t we just use solid, nonadjustable lifters? The answer is yes, and many engines used for racing, aircraft, lawnmowers and such run with solid lifters. The advantages of running solid include reduced valvetrain mass (racing, aircraft), lower cost (lawnmowers). The disadvantage, clearance adjustments are critical for proper valvetrain operation and have to be checked on a regular schedule. This clearance adjustment requires a number of factors to be taken into account to pick the proper numbers. They include thermal growth and wear. The set clearance needs to be adjusted as the engine accumulates time due to normal wear and erosion of valve face and seat. There is a procedure that needs to be followed to set the initial clearance and for the scheduled checks.

The advantage of the hydraulic lifter is easy to understand. Properly setup they will self-adjust for wear and erosion over the life of the engine without any manual adjustments.

I won’t go into the detailed history of the hydraulic lifter other than to say it was one of the biggest advancements to the four stroke engine.

The current hydraulic lifters are nothing short of amazing. The machining and assembly details are astonishing feats. They have the tightest and most detailed specifications used in the LS engines compared to all the other engine components.

So, how can any manufacture mass produce something with these demanding specifications? Just holding tight machining tolerances isn’t good enough. The only way this can be pulled off is using select fit builds. After the machining and cleaning, each component of a lifter, is measured and cataloged in a computer inventory. During assembly the computer will match the proper parts to achieve a perfect fit. Then each assembled piece goes through a series of test to insure proper operation. Part of continuous improvement, the tolerances once reserved for high performance engines, like the LS7, or LS9 are now shared for ALL LS engines. If you order from a dealer a set of hydraulic lifters for your 10 year old plus LS1, you will receive the same exact lifter found in a new LS7, or LS9. Some folks that market so called “performance lifters” might not want you to know this little fun fact.

Noise due to wrong valvetrain geometry

The modern hydraulic lifter is capable of operation in a large dimensional range compared to any solid lifter. This range is about 2.5mm (.098”). Anything out of this range can make noise. Things that cause this include improper valvetrain geometry, failed components like cam lobe, or rocker, and even a bent push rod. A weak or broken valve spring may cause the valvetrain components to be out of phase with each other allowing them to separate and impact as they crash together again.

Noise due to lack of supply oil

One of the side benefits of the hydraulic lifter, due to their sensitivity to oil pressure, they are one of the first clues that your engine has lost oil pressure. The lifter noise made when there isn’t adequate oil will get the attention of even the non-mechanical folks. Just by the sound they know something bad is happening. Shutting down the engine soon enough can save it.

Other reasons for lack of oil include bad oil pump, stuck oil pump relief valve, low oil level, or something wrong with the oil pickup tube system.

Noise due to oil aeration

This might still falls under lack of supply oil. Oil is capable of holding air in suspension. At high engine rpms the windage from the crankshaft and other moving components can aerate the oil enough that once the engine is shutdown, the oil inside the lifters can release this entrapped air into the high pressure chamber of the lifter. Now, on the next cold start the lifters can compress enough to allow valvetrain components to separate during initial start and clatter for a short time until the air works its way out. Normally this only takes 30 seconds to no more than 2 minutes.

Debris in the lifter

This is far less common compared to other reason for lifter noise. In fact I’ve only seen this on new builds. The lifters found with this issue were traced back to plastic fragments matching the lifter carrier. When the lifter is inserted in the carrier the body of the lifter could scrape plastic off and fall into the pushrod sock. The part I never could understand is how this could find its way down into the high pressure chamber of the lifter.

red-in-la

Thanks. Great background.

Looking at the diagram could we add a weak check valve spring to ths list? Thinking oil would drain out overnight if this where weak.

I remember the VW / Porsche engines with the solid lifters we use to have to check / adjust every 3k miles.... Or else.

Havoc40

I agree with everything so far, especially debris. But your forgetting a couple important factors in what causes noise.

The sizing of the piston to lifter bore is the most crucial. That's what determines the hydraulic rate or valving if you will. This is specified as the "leakdown rate". If the leakdown rate is too fast for a given set-up, the piston will bottom out on the shoulder of the lifter body. This is what causes the famous lifter tick after high mileage. If the piston bottoms out, the valves are not fully opening and power will be down. Albeit, you'll probably have good vacuum and low end torque if your rings are sealing lol.

ETA: Didn't read your part in their about holding tolerances, sorry. Holding tight tolerances is only half the story when it comes to lifter assembly/manufacturing.

Maxwell Power

would you happen to have any data on the CTSVR lifter? PN88958689

Curious what the specs are and if the preload is different.

Thanks!

Cobra4B

So when a lifter is "collapsed" what has actually failed? What's happening?

When someone says they have valve train noise at start-up due to "bleed down" what is happening? Are lifters supposed to retain oil?

When you set pre-load are you supposed to have the lifters full of oil? How do you achieve that if the engine is new or if the car has been sitting a long time?

davenp

Just like the rest of the pressurized oiling system, the lifters should remain liquid full when the engine is not operating. All of the void space in the depictions above should be liquid full and should remain so whether the engine is operating or not.

If the clearances become too great, the pressure chamber cannot contain enough pressurized oil to keep the lifter expanded in the valve train when the lifter is tracking the cam lobe. this allows the lifter to compress the spring shown at the bottom (that spring is not designed to help the lifter during operation, it is only a chamber positioning spring when the cam is on the base circle)

Lifter noise at start up is usually very short lived because oil pressure is usually immediate in an engine which has not been disturbed (due to check valves in the lifters and other places in the lubrication system).

During operation, the lifter floats in its bore, the socket and plunger slide in the body. This sliding is not designed to have any meaningful metal to metal contact, however, operating time and dynamic conditions periodically allow this contact and associated wear. As with other highly sensitive tolerances in a pressured system, the more it wears the faster it will continue to wear (valve guides anyone?). This and/or other clearance changes reduce the efficiency of the pressurized volume (local oil pressure gets too low) to a point where it's initial or sustained pressure is no longer adequate.

Even if the engine still has great oil pressure, the flow into this area may not be sufficient to keep that lifter in a state needed to contain the valve train.

Murphy27

I'm also curious about the Caddie lifters. I think most of the problems with lifters are due to improper geometry; incorrect pushrod length and a misunderstanding of proper preload.