I frequently read that a ticking sound from the motor could be a bent pushrod, bad rocker arm, or collapsed lifter. My past experience with hydraulic lifters have been the flat tappet type. I have floated them and they have recovered. Why don't the LS lifters recover?

 

Floating is when there isn't enough spring pressure and the lifter won't go all the way back down and remain in contact with the cam lobes. This is a spring problem.

Collapsed is when the lifter won't pump up. I've had a few flat tappet lifters do this.

 

My collapsed lifters made a clanking noise, not so much a ticking noise. It was a disasterous noise that I do not wish to hear again.

 

I understand what a collapsed lifter is. I am wondering why the LS lifters don't recover. The nature of a hydraulic lifter is that of one kept at operating height by oil pressure. There must be a part or parts that fail for the lifter not to recover oil pressure. My surprise it this in not rocket science involved here. Hydraulic lifters have been around for decades. Just seems weird that all the years of LS motors and no change in design until recently. Maybe I am beating a dead horse with this question?

 

Every lifter that Ive seen fail had an aftermarket cam under it. The only aftermarket lifters Ive seen fail with an aftermarket cam in an gen III was either comp R's or solid lifters.

 

I didn't have a cam when mine failed. The ls lifters are much less likely to fail than the traditional lifters. That is partially why they are under the heads from what I understand.

 

Ok, I can see how using a smaller base circle cam and then reinstalling stock length pushrods and fixed rockers could really cause major problems. The same would be true for really big cams, and RPM's higher than the design allows. I wonder at what RPM they float? Most flat tappet hydraulics are limited to around 6K rpm.

 

They don't recover because they fail. Something breaks or blocks the proportioning valve.

The reason your lifters recovered from floating is because floating a lifter is something totally different that is a result of a weak spring and not lifter failure.

Floating and collapsing a lifter are apples and oranges and can not be compared. To try and compare them by wanting to know why one recoved and the ohter didn't is like comparing an engine that bent a push rod to one that threw a rod.

The reason why you don't see collpased lifters with Gen 1&2 engines is that people usually change the lifters when changing the cam. Gen 3 you have to remove the heads to do this so most don't change them. Because of this, stock Gen 1&2 lifters also don't see the higher RPM, and lifts that Gen 3's tend to see. Look at the big a$$ cams people are putting in their cam only LS1's w/stock lifters.

That said, I have had flat tappet lifters collapse in a 350 and they were designed for the cam and valves I used.

 

Greed, I miss used the word float. I guess I have just been lucky over the years. I started driving in 1960. Had many performance cars with hydraulic lifters. Even did a bit of racing with hydraulic cams.