Flat again

[rudolf35]

My 2010 Griso is still using the flat tappets. I inspected them at 12k and all was well. Now I know all about which kit to use and that the world will end if I do not roller it; But! I had a thought, what about flat replacement tappets? In the last years Guzzi should have upgraded the hardning of them.

Thoughts? 

[Kiwi_Roy]

Don't the flat tappets wear on 4 Valve heads because of the additional forces involved.

My 130,000 mile Eldorado has flat tappets, they show some signs of wear but I'm not in the least worried

No doubt Pete will be along to sort us out.

[oldbike54]

 I believe the cams will still self destruct .

 Dusty

[Bisbonian]

Guzzi went through a few versions of the flat tappets before they went all in with the rollers.

[Wayne Orwig]

I think the last change was in 2009 when they went to the DLC coating. Which as we now know usually fails eventually.
There was a change in there to shim cam end float, but nothing that I know of to the cam or tappet material.

[Markcarovilli]

Don't the flat tappets wear on 4 Valve heads because of the additional forces involved.

My 130,000 mile Eldorado has flat tappets, they show some signs of wear but I'm not in the least worried

No doubt Pete will be along to sort us out.

Well your old Eldo had chrome bores = today's equiv is DLC coating......

You fixed the Eldo correct?

Mark

[pete roper]

Interesting that you found 'No Damage' at 12.5K miles because since I started inspecting every one that comes in I have not found a single one that would pass muster.

I think that a lot of people, including some who should know better believe that there is such a thing as 'Acceptable wear'. There isn't.

A typical example might be the tappets on the right in this pic

(Note, on my desktop the picture is one way up, on my iPad it's the other anyway, it's the ones with least DLC missing I'm referring to.)



"Oh, there's only a teeny weeny bit of DLC missing, they're OK." No they aren't. Long before they get to that stage they've had it. The early signs are not even missing DLC exposing the steel beneath. it's a discolouration of the coating caused by it crazing and fragmenting but it hasn't started to de-laninate yet.

Note also the way it is the nose circles of the cams that begin to discolour and abrade rather than the opening flanks as one would expect.



Unfortunately I've deleted most of my tappet pics, I'm sick of looking at them, but the early stages will simply show two different shades of 'Black' in the DLC. Usually with a lighter band around the circumference of the tappet foot. Even this is a suitable sign for the onset of degeneracy and I've had kits supplied for bikes with only this damage apparent. There is no need to wait until the feet of the tappets are completely scalloped out and the motor is full of iron filings to seek redress. In fact doing so will have dangerous consequences.

Pete

[rudolf35]

OK, hint taken. When the weather goes bad it will be takedown and roller time - "C" kit; no white dot on the back of the head.
       

[Kiwi_Roy]

Pete, might I be so bold as to ask how millions of engines have run forever without damage, I'm talking about auto engines as well.

They don't use DLC do they?

It seems to me there should be no metal to metal contact, isn't that the job of the oil to keep the metal bits apart?

How long will it be before those little rollers spinning around at thousands of revs a minute start to wear out?

I'm not trying to be smart I just want to understand.

Perhaps if we understood the design of the rollers it might help.

[lucky phil]

Pete, might I be so bold as to ask how millions of engines have run forever without damage, I'm talking about auto engines as well.

They don't use DLC do they?

It seems to me there should be no metal to metal contact, isn't that the job of the oil to keep the metal bits apart?

How long will it be before those little rollers spinning around at thousands of revs a minute start to wear out?

I'm not trying to be smart I just want to understand.

Perhaps if we understood the design of the rollers it might help.

Flat tappet car engines work ok at the lower revs and mild cam profiles they tend to have, however even Chev engines since the Gen111 and before have gone to rollers. In comp engines with flat tappets (due to regulations) keeping the tappets alive is a significant issue and running in the cams and lifters with single cam springs is usually required. 
The major factor with the Guzzi it seems is the flat tappets were wearing due to "who knows what" ( insert your own theory inc manonaise due to condensation or maybe production tolerances with the cam lobe offset and taper V the radias on the lifter, who knows) so they went to DLC which even I with 1/2 hour of internet research for my own high cam flat tappet engine build thought wasn't a sensible option to use on lifters.
Flat lifters don't actually wear initially they fatigue, whether DLC or hard facing it fatigues then breaks away from the base material exposing that then its a downward spiral taking out the cam lobe as well. The nice thing about the DLC is that it then circulates around the oil system and takes out the big ends and mains as well. Forget the oil filter as many don't filter below 30 microns and 5 microns will cause plain bearing damage. Give that a thought next time you buy your dime store filter.   
You wont have to worry about a hardened steel roller on a hardened steel pin with plenty of lubrication wearing out any time soon, plus you can run more aggressive cam profiles as well.
Ciao

[rocker59]

Flat tappet car engines work ok at the lower revs and mild cam profiles they tend to have, however even Chev engines since the Gen111 and before have gone to rollers.

Playing Devil's advocate, here:  Why has my Sport 1100 survived so long with its fairly radical OEM Crane came and flat tappets?  And all the late LeMans 1000s running around with B10 cams?

Yes, rollerizing hotrodded Chevy engines has been around forever.  We rollerized my cousin's Chevy II bracket racer 30 years ago.  Dual quad tunnel ram 355 small block, top loader 4-speed and 9-inch rear end.  It's fast.

[Waltr]

Pete, might I be so bold as to ask how millions of engines have run forever without damage, I'm talking about auto engines as well.

They don't use DLC do they?

It seems to me there should be no metal to metal contact, isn't that the job of the oil to keep the metal bits apart?

How long will it be before those little rollers spinning around at thousands of revs a minute start to wear out?

I'm not trying to be smart I just want to understand.

Perhaps if we understood the design of the rollers it might help.

I had a boss that would always say to me "understanding is the Booby Prive in life." 

The reason that this is a problem is the coating was to never wear off.  If the DLC maintained integrity it would not have a problem. The metal below the DLC is not to spec as a tappet material and therefore we get what we get.
The cylinder walls are coated with NicaSil, not DLC.

[Kiwi_Roy]

No ones answered the question, why are the cams and tappets wearing, surely they are not supposed to touch.
The big ends don't touch the crank, they are separated by a layer of oil that stops them touching, they wouldn't last 10 seconds without it. The rear drive has enormous forces between the ring gear and pinion, the oil is good enough to keep those from wearing.

Surely the cams and tappets should be the same.

Why is the DLC wearing?

Why don't the roller tappets wear also, are they better lubed?

[oldbike54]

No ones answered the question, why are the cams and tappets wearing, surely they are not supposed to touch.
The big ends don't touch the crank, they are separated by a layer of oil that stops them touching, they wouldn't last 10 seconds without it. The rear drive has enormous forces between the ring gear and pinion, the oil is good enough to keep those from wearing.

Surely the cams and tappets should be the same.

Why is the DLC wearing?


Why don't the roller tappets wear also, are they better lubed?

 Roy , yes there is always supposed to be a few microns of oil preventing metal to metal contact , but my understanding is that even thin there is some friction generated heat . No idea why the DLC is failing , that is a question for an engineer .

 About the roller tappets being better , roller tappets don't hammer on the moving parts like flat tappets do . Much gentler take up , no "bang" as things come in contact .

 Dusty

[tazio]

God's teeth ! (always wanted to say that. Thanks Mr.Roper! )

[Kiwi_Roy]

God's teeth ! (always wanted to say that. Thanks Mr.Roper! )

Oh sure, we can just accept something and shutup, or we can wonder why.
Flat tappets worked for eons before the invent of DLC

Could it be that the manufacturer is just pushing the technology too far changing the cam profile until something gives

Dusty's explanation of roller tappets gives us a clue, is the cam profile different for a roller tappet.

Can we not have a debate here?

Something went wrong between Rocker59s Sport 1100 and the Griso, why not take a step back instead of sideways?

[tazio]

Whoa,Nellie! Just pokin' fun. Been down this rabbit hole, asked a few to many questions
and voiced a few unpopular opinions. Finally traded in my flattie '10 Stelvio for total piece of mind,
a 2015 Griso.
Already quite a bit of conjecture on this subject here at the 'ol wild goose over the past year(s).
But don't let my sense of humor derail anyone wanting to pursue this topic...

[pete roper]

Roy, I have my theory as to why they go tits. I've revised it several times as new evidence comes to hand but at the end of the day the evidence fits the theory. Is it right? I don't know! But it's not worth me re-stating it here again as it invariably causes rancour and I end up getting trolled by clueless phesterheads. I simply can't be bothered.

Also the Chev refference? So these use roller tappets? I thought they used roller rockers to negate side loadings on the valves rather than roller tappets? Plenty of engines out there with roller tappets though and they are hardly an unknown quantity any more than flats.

Once again I think the biggest issue here is the I ate conservatism of yer average Guzzi owner many of whom refuse to believe any technology developed after the First World War has any merit.

Pete

[Don G]

The lobe profile on roller cams are radically different the flat tappet cams, more rounded. I have been told by Comp Cams that with a radical flat tappet cam and heavy springs that lobe load can approach or surpass 100,000 PSI. Even roller cams can fail under that extreme operating parameter, hope your oil is up to snuff! DonG

[mtiberio]

fact is, all the flat tappets from loop onward need to be watched. the removal of zinc from oil has put the tappet to cam interface at risk.

[Don G]

The reason the auto manufacturers went to roller cam trains is due to the fact that the oil formulation had to change because zinc etc. was polluting the catalytic convertors. Cant run flats without the heavy metal additives so they went to rollers. DonG

[Kiwi_Roy]

Well gentlemen, it was an interesting debate, I learned quite a bit in the process, I hope others did also.

Tazio, no offence taken, I kind of figured LOL
Thanks Lucky Phil, Rocker, Waltr, Pete, Don G, Dusty, Mtiberio and others.

I think I'll stick to Electrickery
Perhaps one day we will have electrically activated valves timed by the ECU

Don G wrote
The reason the auto manufacturers went to roller cam trains is due to the fact that the oil formulation had to change because zinc etc. was polluting the catalytic convertors. Cant run flats without the heavy metal additives so they went to rollers. DonG  Is that really why?

Cheers
Roy

 

[lucky phil]

Roy, I have my theory as to why they go tits. I've revised it several times as new evidence comes to hand but at the end of the day the evidence fits the theory. Is it right? I don't know! But it's not worth me re-stating it here again as it invariably causes rancour and I end up getting trolled by clueless phesterheads. I simply can't be bothered.

Also the Chev refference? So these use roller tappets? I thought they used roller rockers to negate side loadings on the valves rather than roller tappets? Plenty of engines out there with roller tappets though and they are hardly an unknown quantity any more than flats.

Once again I think the biggest issue here is the I ate conservatism of yer average Guzzi owner many of whom refuse to believe any technology developed after the First World War has any merit.

Pete

Later Chev motors have both Pete,roller rockers and roller lifters. Roller lifters have been around a lot longer than zinc being removed from oil and flat tappet lifters don't actually bang or hammer into the cam, that's why the cam has an opening ramp. Flat tappet design is also limited by the dimension of the cam lobe and the lifter foot, a roller lifter can have a more radical profile and a lesser dimension so it doesnt take up as much real estate.
As for wear, well I mentioned it in my first post, the initial issue is USUALLY not metal to metal contact ( although it can be) its sub surface fatigue of the hardened face, pieces then break off and then its a grinding paste process on softer cam base material. Oil film wont help to any great extent this fatigue issue,its materials and or design problem. 

Ciao 

[Don G]

Roy: That is exactly why, flat tappets are cheaper and rollers more expensive to manufacture also. Rollers use a different lobe profile so they can get away with running less radical lobe shape, they allow better cylinder filling over a longer duration using less lift, which in turn is easier on the valve train. Perhaps Guzzi should have employed a North American cam company like they did in the past to design something that would work. Kind of like , no money to do it right the first time, but lots of money to do it right the second time.......  DonG

[pete roper]

The ZDDP argument is a red herring with DLC coated followers. In fact in some studies it had been found to be counter productive.

Phil is right on the money with his comments about what causes the coating to delaminate. It is my belief that the nature of tha cam profiles causes the tappet to momentarily leave the cam as it approaches the end of the opening flank and the beehive springs don't adequately control the vale. This will only happen at certain engine speeds where the accelerative forces and harmonics combine to enable it to happen but then the tappet slams back down onto the nose circle. That is why you get discolouration and damage first on the nose circles of the cam rather than on the much more heavily loaded opening flanks.

This hammering of the tappet surface causes the DLC to craze and this in turn will allow moisture to penetrate it to the ferous base which will encourage the delamination as the base oxidises. It would also explain why the problem manifests itself quicker in cooler, damper climates due to the gross over cooling of the 8V motor. You can see the effect of the crazing on young tappets which develop a Matt colour to their surface before the coating begins to delaminate.

Pete