Flat tappet lifters, wear patterns, cam lobe taper and other things. Let's swap opinions and ideas.

[BSB67]

Geoff - To your original comment/question regarding less contact mileage between the lifter and lobe on a re-grind/smaller base being potentially better - I don't know.

But for a given lobe profile/lobe area, the smaller the base circle, the harder the lobe whacks the lifter. The contact patch effectively moves further out on the lifter surface, kinda like a faster rate lobe would, but its not a faster rate lobe. I think this would be less beneficial.

 

[Geoff 2]

Thanks for the reply. I do not see a problem with the contact patch moving further out on the lifter surface. The actual contact area is very small because of the lobe taper/crown on the lifter. It is so small that the oil gets squeezed out because of the high, concentrated load; the end result is the wear on the lobes & lifters.....
The benefit I see with a smaller lobe is:
- the lifter is in contact with the lobe over a lesser distance & for a shorter time.
- since the wear comes from contact of the two parts, reducing the time they are in contact should improve component life.
- the speed of the lifter travelling around the lobe will be less with a smaller lobe. This should reduce friction. Friction causes heat. Reducing friction [ heat ] should help the oil film survive between the parts.

 

[Krooser]

Most of us have heard of how engines with flat tappet camshafts have had increased failures in the past 15-20 years. There are a bunch of opinions on what is to blame but so far, I have seen no 100% smoking gun on the exact cause. The potential causes are numerous.
Reduced zinc in oil.
Camshafts and lifters made with softer metal than before.
Lower quality machining from Chinese factories.
Lifters that don't spin in the bores.
Valvesprings too stiff.
Improper break in.
Etc, etc....
While all of those things may be true AND if you have more than one of those situations together, the chances of a failure seem to grow exponentially.
I know that there are several threads on this site covering this topic, I was hoping to expand a bit on what has already been mentioned.
Being one with a curious mind, I wonder about a few things...
We have been told that with flat tappet systems, the lifters mate to the lobes. How? I've read that they establish a pattern to each other and that to swap in another lifter, it must be NEW and that the "break in" starts all over for that lifter.
Why? Has anyone ever published pictures and measurements of the actual wear patterns?
Who remembers Jim LaRoy/IQ52 ? he mentioned before that he has swapped lifters around and even reused them in dyno testing and had no failures. How is this possible?
I remember a buddy going out to the junkyard and pulling a couple lifters from an engine to swap into his engine. He had a couple sticky lifters in an old beater. I don't recall any future troubles that he had.
I did the same to a stock 318 years ago.

Interestingly...in the Cummins 6.7 world the roller lifter failures have created a market for retrofit mushroom flat tappet conversions!!!

Better reliability and less cost!

 

[Ceedawg]

Ceedawg,
I also know who is talking rubbish....& it is not me. Do you think when they regrind a cam they only grind the base circle area......& leave the rest of the worn lobe untouched & blend it into the newly ground section?????????? Ready to destroy the new lifters that will be used because the lobe taper has been worn away? You must be really dumb if you think that.

Do you really believe the cam grinders would use worn out cams?

 

[Kern Dog]

A buddy and I have been building engines side by side in my backyard shop. Mine is a 1990 360 for my 67 Dart, his is a 5.9/408 for his 68 Dart. Both engines were built with roller camshafts when new which is a great thing.
We degreed his cam and it got me thinking…. We check timing events and centerline on cylinder #1 but nobody ever checks the other cylinders? We all just trust that all 16 lobes are ground correctly and in the proper position?

 

[Ceedawg]

I’m sending a solid Hemi cam to have it ground for hydraulic lifters. I’ll ask if he grinds the lobes on same angle as the mopar lifters. Might send an NOS lifter with cam. Oregon Cams

 

[padam]

I’m sending a solid Hemi cam to have it ground for hydraulic lifters. I’ll ask if he grinds the lobes on same taper as the mopar lifters. Might send an NOS lifter with cam. Oregon Cams

The cam lobe is ground with a taper, or angle. The surface is flat. It’s tough to measure with a micrometer but is was getting.002”-.003” on my latest comp SFT.

The lifter bottom is supposed to have a radius (like a dome or crown.) I’ve seen the number 14” radius out there, but don’t know if that’s true (maybe for Chevy. ) the lifters I have measured have .002” to .0025” crown.

From what I understand this, along with the lifters being off center of the lobe, is supposed to have the effect of spinning the lifters while pushing the cam towards the rear of the engine.

What I noticed on my latest cam installation is that the cam lobes don’t line up the same with all of the lifters. If I weren’t in a hurry I would take more measurements.

I do have a Lunati cam that was new in 2021. I can compare it to an old DC cam from the 80’s when I get around to it.

Might they be using cam cores that are cast “close enough” to fit more than one application?

 

[Ceedawg]

The cam lobe is ground with a taper, or angle. The surface is flat. It’s tough to measure with a micrometer but is was getting.002”-.003” on my latest comp SFT.

The lifter bottom is supposed to have a radius (like a dome or crown.) I’ve seen the number 14” radius out there, but don’t know if that’s true (maybe for Chevy. ) the lifters I have measured have .002” to .0025” crown.

From what I understand this, along with the lifters being off center of the lobe, is supposed to have the effect of spinning the lifters while pushing the cam towards the rear of the engine.

What I noticed on my latest cam installation is that the cam lobes don’t line up the same with all of the lifters. If I weren’t in a hurry I would take more measurements.

I do have a Lunati cam that was new in 2021. I can compare it to an old DC cam from the 80’s when I get around to it.

Might they be using cam cores that are cast “close enough” to fit more than one application?

The cam I’m sending is a Lunati, maybe 25 years old. But still never installed.

 

[Kern Dog]

I thought that the direction of the distributor drive/intermediate shaft also determined the direction that the cam gets pushed whether forward or rearward.
The small blocks have the distributor at the rear on the left side of the cam and spin clockwise. The small blocks do have the luxury of a thrust plate to limit fore/aft travel.
The B/RB is at the right front and spins counterclockwise. I don't have instruments sensitive enough to measure the taper of a cam lobe but I'd guess if the lobes were higher at the front of each lobe, the cam would be pushed forward.
This matters to me because I decided to switch to a roller cam in my 440/495. The timing set I got has a Torrington bearing on the back side so the sprocket stays in contact with the face of the block. That controls the aft movement. I need to put a thrust button at the front with (What I thought I recall) a mere .010 clearance between the button and timing cover. Ten thousands seems awfully tight. Not trying to be a hack but it seems like the cam should be able to move more than that without causing trouble but that is just my curious side thinking.....

 

[Ceedawg]

I thought that the direction of the distributor drive/intermediate shaft also determined the direction that the cam gets pushed whether forward or rearward.
The small blocks have the distributor at the rear on the left side of the cam and spin clockwise. The small blocks do have the luxury of a thrust plate to limit fore/aft travel.
The B/RB is at the right front and spins counterclockwise. I don't have instruments sensitive enough to measure the taper of a cam lobe but I'd guess if the lobes were higher at the front of each lobe, the cam would be pushed forward.
This matters to me because I decided to switch to a roller cam in my 440/495. The timing set I got has a Torrington bearing on the back side so the sprocket stays in contact with the face of the block. That controls the aft movement. I need to put a thrust button at the front with (What I thought I recall) a mere .010 clearance between the button and timing cover. Ten thousands seems awfully tight. Not trying to be a hack but it seems like the cam should be able to move more than that without causing trouble but that is just my curious side thinking.....

Remember turning the OIL PUMP, because of the teeth direction, this forces the cam back into the engine, like setting your feet to push anything. No button is needed unless you’re using a roller cam because the angle on lobe and lifter of a flat tappet moves it backward too but not as much as the pump. One can imagine how much force is applied at 80 psi and heavy oil. If you’ve primed an engine with a drill you know.

 

[Kern Dog]

Thanks. I'm curious though....flat tappet camshafts ALL get pushed to the rear?
No offense....I'm not disputing you, I would like to know for sure....maybe from a cam grinder?

 

[Ceedawg]

Thanks. I'm curious though....flat tappet camshafts ALL get pushed to the rear?
No offense....I'm not disputing you, I would like to know for sure....maybe from a cam grinder?

No offense taken, one of the laws of motion, an equal and apposite reaction occurs.

 

[70ChargerRT]

Interestingly...in the Cummins 6.7 world the roller lifter failures have created a market for retrofit mushroom flat tappet conversions!!!

Better reliability and less cost!

Well when oil samples were drawn its been found that 15/40 was used in almost all of those lifter failures. Even RAM put out a bulletin about the oil. There’s absolutely thousands of those 6.7 trucks running the correct oil with over 300k miles with zero issues but some people don’t buy the oil weight issue. Id be more worried about the grid heater than anything. I was running the wrong oil in my hr lifters compared to what morel recommends. Did it attribute to my lifter failure? IDK. Maybe but in saying that all HR lifters aren’t created equal but just take a look at the old 7.3 powerstrokes. They’ve always used HR lifters and you never ever here about lifter failures in those trucks. Ever. Is it a parts issue? Look at all of the lifter problems the gen 3 Hemis and LS motors have. Even Comp. Ill be going back to HR lifters but ill be using Johnson this time with a little bit different valve train set up.

 

[Kern Dog]

I've been surprised to read that high Zinc oil is still being advised for use in roller camshaft applications.
Why? Isn't the roller wheel the magic fix for the cam and lifter failures?

 

[70ChargerRT]

I've been surprised to read that high Zinc oil is still being advised for use in roller camshaft applications.
Why? Isn't the roller wheel the magic fix for the cam and lifter failures?

I thought it was only advised for only higher spring rate applications in rollers but exactly what that it is I dont know.

 

[Ceedawg]

Well when oil samples were drawn its been found that 15/40 was used in almost all of those lifter failures. Even RAM put out a bulletin about the oil. There’s absolutely thousands of those 6.7 trucks running the correct oil with over 300k miles with zero issues but some people don’t buy the oil weight issue. Id be more worried about the grid heater than anything. I was running the wrong oil in my hr lifters compared to what morel recommends. Did it attribute to my lifter failure? IDK. Maybe but in saying that all HR lifters aren’t created equal but just take a look at the old 7.3 powerstrokes. They’ve always used HR lifters and you never ever here about lifter failures in those trucks. Ever. Is it a parts issue? Look at all of the lifter problems the gen 3 Hemis and LS motors have. Even Comp. Ill be going back to HR lifters but ill be using Johnson this time with a little bit different valve train set up.

What weight-brand oil is recommended if not 15/40?

 

[70ChargerRT]

What weight-brand oil is recommended if not 15/40?

10/30 HD Diesel Synthetic. I run T-6 Rotella. Anything below zero F* 5/40.

 

[Ceedawg]

10/30 HD Diesel Synthetic. I run T-6 Rotella. Anything below zero F* 5/40.

What I run Rotella 15/40 in my 06

 

[70ChargerRT]

What I run Rotella 10/40 in my 06

All of my guys that work for me run 15/40 in their pre 19 trucks. I still run 15/40 conventional in my 99.5 powerstroke, 09 Kubota tractor and my 09 Cat Dozer. I was wanting to run 15/40 in my 23 HO Cummins because I can usually get my oil for free off of the grease truck when I’m working lol.

 

[RemCharger]

Well when oil samples were drawn its been found that 15/40 was used in almost all of those lifter failures. Even RAM put out a bulletin about the oil. There’s absolutely thousands of those 6.7 trucks running the correct oil with over 300k miles with zero issues but some people don’t buy the oil weight issue. Id be more worried about the grid heater than anything. I was running the wrong oil in my hr lifters compared to what morel recommends. Did it attribute to my lifter failure? IDK. Maybe but in saying that all HR lifters aren’t created equal but just take a look at the old 7.3 powerstrokes. They’ve always used HR lifters and you never ever here about lifter failures in those trucks. Ever. Is it a parts issue? Look at all of the lifter problems the gen 3 Hemis and LS motors have. Even Comp. Ill be going back to HR lifters but ill be using Johnson this time with a little bit different valve train set up.

Diesels are different animals. Low rpm, small cam, lighter springs etc.