How do hydraulic flat tappet lifters fail?

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@PRH do you attribute any particular type of lifter with some or all of the common failures?

Honestly, on the situations where I’ve gotten to see the pieces first hand, and/or after discussions with the owners......... I’d say most of the time I’ve narrowed it down to a problem with the cam, or break in, or oil.
I can only recall one instance where I was really confident the lifters themselves were the reason for the failure....... and in that particular instance....... it was pretty obvious.
That was right near the beginning of the whole lifter debacle in the early 2000’s.
 
I'm suspect of a lot of modern speed part quality. In the 80's and 90's if you wiped a lobe on a performance cam it was usually installer and break in error. But they were much more forgiving.
I watched a comp cam and lifters eat themselves in a 383 with flawless break in. I didn't assemble it so I can't say all assembly was perfect but it was a well respected professional.

Other than proper break in the only extra precautions we took, back when I was building these things,was to run a small ball hone in the lifter bores and round any sharp edges.
I recall new lifters would sometimes mic very slightly fatter that used ones. I also figured the pattern the hone would put in the bored would encourage lifter rotation.

The last time I mentioned that to the internet hive mind I was told how wrong that procedure was and I'm so stupid it's a miracle I can breathe.

But I've never lost a cam in anything I ever built doing this. But your mileage may vary.
 
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The short answer is...... a lobe profile that’s designed to use up the entire area of the lifter has less room for any kind of misalignment or misplacement of the lifter bore in the block.

Depending on the particular block, this can be a big problem.

Quite a few years ago a group of people from Moparts got together and fielded an entry into one of the Enginemasters competitions(2001-2002 maybe??).
The rules that year mandated flat tappet cams.
We used fast rate .904 solid lifter lobe designs........ two of which promptly failed in short order on the dyno.

The motor was diassembled and the block brought to a shop for lifter bore correction(bushings).
The guy who performed the operation said several of the bores were .030+ out of position.
Since the lobe profiles were designed to come within .015-ish of the edge of the lifter, that situation was never going to work.
After the lifter bores were corrected...... no more cam failures.

So, by using a lobe designed to work with a smaller diameter lifter, there is a bigger margin for error with regards to lifter bore placement before the edge of the lifter is digging into the flank of the cam lobe.

Yes, there is a potential to make more power with a lobe profile designed to utilize the full diameter of the lifter....... but it has to live first.

At this stage of the game....... would you trade say...... 10hp to have been able to avoid what you’re going through now?

I have no idea if that’s what caused your failure or not, but moving forward I’d try and stack the deck in your favor if I were you........ and not using a fast rate .904 is one more item that can be applied towards that end.
Thanks a lot for the education. I think one of the most important lessons I’ve had to learn is that bigger is not always better when it comes to building an engine. Even with as mild a build as mine is, it might behoove me to tone down at least the cam to what you’ve suggested.
 
While we’re here, can I make a pitch for solid flat tappet and adjustable rockers. You need a cam/lifters and some of your rockers need attention or replacement. What you really don’t want is to replace the cam/lifters and it survives the break in, but it starts to collapse a lifter at moderate rpm. This will cost more for new rockers, but you will not have to worry about a lifter collapsing or pumping up. The maintenance on a solid lifter is over stated. Once they settle in they don’t change much. Check them once a year. Think of it like a physical for your engine. Also for a somewhat inexperienced person, you become more comfortable working on it and if the lash starts to open up, you might stop a small issue from turning into a big issue. Just my 2 cents.
 
. I think one of the most important lessons I’ve had to learn is that bigger is not always better when it comes to building an engine.

What goes right along with that is........
Sometimes..... less is more.
 
I hate to beat a dead horse, but I was reading an oil viscosity chart, and I think I may be running the wrong oil. This chart gives suggestions according to bearing clearances, and my main bearing clearances were .002". According to the chart, I should run 20 weight or 30 weight. I was running 40 weight. Would that cause an oiling problem at higher RPMs or higher temps?
 
I hate to beat a dead horse, but I was reading an oil viscosity chart, and I think I may be running the wrong oil. This chart gives suggestions according to bearing clearances, and my main bearing clearances were .002". According to the chart, I should run 20 weight or 30 weight. I was running 40 weight. Would that cause an oiling problem at higher RPMs or higher temps?
No not like that, not that fast! The lifter didn't rotate for whatever reason. That probably started day one.
 
No not like that, not that fast! The lifter didn't rotate for whatever reason. That probably started day one.
Thanks. A couple questions on the bores - am I right to say they should be .906" for .904" lifters? And what should the surface be on the walls of the bore? Mine aren't machined smooth to a shiny bright finish, but they aren't rough and pitted either.
 
Thanks. A couple questions on the bores - am I right to say they should be .906" for .904" lifters? And what should the surface be on the walls of the bore? Mine aren't machined smooth to a shiny bright finish, but they aren't rough and pitted either.


The bore is nominal. The lifter is under nominal by what the clearance SHOULD be.
 
Thanks. A couple questions on the bores - am I right to say they should be .906" for .904" lifters? And what should the surface be on the walls of the bore? Mine aren't machined smooth to a shiny bright finish, but they aren't rough and pitted either.

Lifter bore is .904. Lifter diameter is .903.
 
The lifters spin because the bottoms of them are not flat, they are slightly concave. That's what causes them to rotate slightly every up and down.
No, the lifters are convex.
If you set them upright on a perfectly flat surface, concave lifters sit still. A convex surface means the middle sits below the edges so they will rock slightly. You can stick a feeler gauge under the edges of a properly machined lifter.
Me? I always have anxiety about a camshaft failure. I had 2 Comp Cams XE285HLs go bad back to back in 2006. Recently, I bought a Comp Cam thinking that maybe they had improved over time and mine looked like THIS:
CC Z 2.jpg

Look at the edges of the lobes on this cam. What you see above is shreds of fabric from when I wiped the lube off to return the cam. There were 7 lobes that had sharp edges from where they didn't properly machine the lobes all the way across. Think of it as a narrow strip of unmowed grass near the street.

Comp 1.JPG

Comp 2.JPG

Comp 3.JPG
Comp 4.JPG


So....I only caught this Because I usually pour the assembly lube in my hand and smear it on the lobes. The edges of the lobes actually cut me in a couple of places. If I had just installed this and then poured the lube through the open sections in the valley, I would have never known. The lifters would have made contact with those sharp edges and failed like yours. The chunks missing at the bottom of the OPs lifters is exactly what could have happened to my 383.
I posted this at FBBO, DodgeCharger.com, 1970ChargerRegistry and Yellow Bullet. The VP of Comp Cams contacted me and apologized. He also said he wanted to make it right. I told him that I understand that stuff happens and that since I caught the problem prior to installation, I'm only out a little time and effort. I didn't post it on the forums to twist their arms to get free stuff, I did it to warn others to closely inspect their stuff when assembling their engines.
I returned the cam to Summit Racing in Nevada and politely declined a replacement.
 
Lifter bore is .904. Lifter diameter is .903.
Wow, I didn’t realize the tolerance was that tight. Half a thou ain’t much.

Look at the edges of the lobes on this cam

That’s not something I would’ve known to look for. While I’m not saying that was the case here, I do remember my cam lobes having pretty sharp edges. I simply attributed it to a freshly machined job. This time I’ll pay close attention and look out for burrs.
 
Okay, here’s the first bearing removed so far. #3 main. Keep in mind I’m replacing all the bearings, but how does this look? What do you guys see? Just getting broken in?

B45E3412-7531-4A2D-B6A0-A927F418D1F1.jpeg
 
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That’s kind of what I was expecting to hear. I have new bearings ordered already, so they were being replaced anyhow. Here’s where my experience is - I know what a completely destroyed bearing looks like, and I know what a brand new bearing looks like. However, learning what they look like after “some wear” or “normal wear” is something I still need to learn.
 
That’s kind of what I was expecting to hear. I have new bearings ordered already, so they were being replaced anyhow. Here’s where my experience is - I know what a completely destroyed bearing looks like, and I know what a brand new bearing looks like. However, learning what they look like after “some wear” or “normal wear” is something I still need to learn.
It looks to me like a lot of uneven wear and like some heavy bedding has occurred.
 
Almost like the material from a flattened cam lobe and lifter was circulating in the oil?
Yes. I wouldn't reuse those bearings. I would take it all apart and start over. Clean, clean, and clean. Then double check everything to make sure it is all correct.
 
This is all wonderful news! Because now I can paint the water pump Chrysler blue like I wanted, and fix that annoying leak at the bell housing.

Heck, I don’t even like driving that car anyway... :lol:
 
And may I state what might be common knowledge? Removing the grill, bumper, and radiator sure does make access to the engine much easier. I don’t think I’ll pull another engine without doing this first.
01C2654C-D8EA-4CF8-B190-359BCD5EBC5A.jpeg
 
That bearing also looks oil starved. What did you use for assembly lube and how much did you use?
 
What does the crank surface look like?
I believe the journals will need to be polished. (In fact, I'm going to have them polished regardless.) I'll post some pics in a bit, but I can just barely see some very light scoring on the surface. I can feel grooves just a couple thousandths deep with my fingernail.

That bearing also looks oil starved. What did you use for assembly lube and how much did you use?
Just a quick squirt o' WD40 and called it good...why do you ask?

I'm kidding. I used the Sta Lube moly assembly lube. On the bearings, I smeared maybe a 1/32" or 1/16" layer with a gloved hand, but I knew a lot would squeeze out. For my education, can I ask what indicators you're seeing that make it look oil starved?
 
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