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Thanks to all for the input. I think that the cost of repair of a wiped cam outweighs the extra expense of a roller. I too would love to get together for some bench racing after vacine.🍺

Don H
your car, your call (of course).

By the way your post is worded looks like you are assuming the chance of wiping a cam is an assured done deal. In reality the vast majority of flat tappet cams are merrily motoring down the road bumping their tappets without incident or injuries.

Roller cam trains are not without their own special set of pitfalls. Many more moving parts that do have a way of unexpected and unexplainable failures.

Z
 

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I don’t see any mention of the EDM lifters. I know CompCams sells them, maybe other do also. They have a small hole in the lifter face. The ones I’ve used have a hole diameter of 0.012”. Others may vary.

with the EDM hole you have pressurized oil squirting out directly into the cam / lifter interface. Fantastic lubrication.

I put a set of these lifters into my latest K code when I installed a Weber friendly cam. I was initially concerned that with 16 lifter holes of 0.012” diameter there might be a drop in oil pressure. I ran the K code pretty hard. Over 25,000 miles on these lifters without any issues. Many of those miles were all day driving at 4,000 to 5,000 rpm hour after hour.

My oil pressure concerns were without merit. The before and after oil pressure, as measured with an permanently installed AutoMeter mechanical gauge, was unchanged. Not even 1 psi lower.

I have a K code so I used the ESM solid lifters, I don’t know if they come in a hydraulic lifter variety

Here is one article about the lifters, A google search will reveal others I’m sure.


Good call. They are mandatory when using a race SFT that requires high rate valve springs. They could be cheap insurance for anyone considering a more conservative flat tappet. I've only seen them for SFTs also.
 

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You know what gets me? You never heard of anyone wiping out a cam in a OHC engine.
there has to be some difference in lubrication.

From the 1972 DOHC Kawasaki Z-1 and the ‘79 Honda CB-750 on to the modern Ducati twins with their separate cams for opening AND positive closing of the valves, I’ve overhauled and adjusted a zillion valves on these flat tappet engines with their inverted bucket shims. First of all, they don’t need valve adjustments very often, and as you point out they don’t wipe cams either. That is also my experience with the Jaguar DOHC engines, starting with my ‘67 and ‘70 e-types (aka XKE’s) and the same with my current DD, a ‘02 XKR Jag. They all have the basic similar valve set up with a non roller, non hydraulic valve train. Just a cam lobe riding directly against the “lifter”, which is an inverted bucket with a shim under the bucket or one on top of it, on which case the cam rides directly on the shim.
In all these decades I’ve never seen a shim or valve bucket that was degraded in the least by the camshaft.

The issues all seem to be with American pushrod flat tappet engines.

The Triumph motorcycle twins of the 1950’s thru 1980’s all had pushrod engines with solid lifters, but the exhaust lifters had oiling holes for pressurized oil directed directly at the lifter - valve interface, exactly like the EDM holes in lifters sold today. They were very long lasting.

Z
 

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I think wiped flat tappet cams might happen a little more often than some of you think. I would love to run a solid flat tappet cam, but my last one cost me too much. As I said before, more aggressive lobe designs an poor quality cores have exacerbated the problems.
BTW Comp recommends using lower tension break-in springs in many cases. That in itself add cost and hassle.
 

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I think wiped flat tappet cams might happen a little more often than some of you think.......”

BTW Comp recommends using lower tension break-in springs in many cases. That in itself add cost and hassle.

I believe the opposite is true. Beside the fact that most cam / lifter issues can be laid directly to the rash of bad lifters a decade ago, there is 50 + years of history & millions of vehicles which serve to demonstrate the successful use of the flat tappet cams.

But the internet never lets anything die. What happened years ago is constantly being regurgitated as current events.

As far as break in springs go, I’ve never used them in countless engine builds, and don’t know anyone who has. I think in the recommendation of them CompCams is just trying to create a red herring, absolving them of any responsibility.


Z
 

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"- There is really no "reduced friction" with a roller cam compared to a flat tappet cam. I know that sounds counterintuitive, the but the reality is flat tappets ride on a layer of oil which has almost no friction."

^^^^^^
This.

Manufacturers went to roller cam because they could open and close the valve faster reducing overlap hence emissions. Pucketa pucketa pucketa sounds cool but it won't pass the sniffer test.
 

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Funny I keep seeing over and over how roller lifters open a valve faster. If you look at the lobe profiles, that isn't really true. Flat tappet profile tappets can be slapped open by a lobe profile that's almost a triangle. A round roller can't ramp up that quick, it's simple geometry. The rollers do gain advantages after that initial opening though. Rumor among the turbo people is that turbos respond well to that ability of a flat tappet to get the valves cracked open quicker. For some that particular gain seems to be worth the tradeoff. But it's all pretty esoteric unless you are putting engines on a dyno or chasing tenths on a racetrack.

I wiped some lobes on a cam once. Eight years after I built it. For some reason I had a time wrapping my head around the failure at the time and kind of refused to believe that's what happened for a while. If it had happened at or right after break-in I would have thought nothing of it. But 50K miles later threw me a bit. It didn't do it again that I know of. Sold it about 10K miles later. A plain jane 1970's 302.
 

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My statements about the opening and closing rates comes straight from comments made by Ford engineer to Car & Driver magazine when the Mustang 5.0 got rollers, back in '85. He said friction reduction was minimal and the primary driver of the change was getting reasonable lift without increasing overlap all with an eye towards passing emission standards. Of course a manufacturer can afford to make nearly invisible changes in exchange for very minimal improvements. Perhaps a flat tappet can achieve opening and closing rates identical to a roller. But for whatever reason, Ford decided to go the roller route.

Also, I recall that in the mid '80's, when the Elliotts were dominating NASCAR in engine power, the sanctioning body was considering having the Ford teams bush their lifters, as Ford lifter bores, as cast, were significantly larger than the GM lifters. And mushroom lifters and rollers were prohibited. Of course, the larger lifter would permit lobe geometry that generated quicker lift without the edge of the lifter digging into the side of the lobe.
 

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Also, I recall that in the mid '80's, when the Elliotts were dominating NASCAR in engine power, the sanctioning body was considering having the Ford teams bush their lifters, as Ford lifter bores, as cast, were significantly larger than the GM lifters. And mushroom lifters and rollers were prohibited. Of course, the larger lifter would permit lobe geometry that generated quicker lift without the edge of the lifter digging into the side of the lobe.
Larger bores also play a role for rollers. A good friend of mine ran SCCA GT1 in the 90's and early 2000s. His car was a Roush ex-Trans Am car. He bought a lot of used parts from Roush. Apparently one of the blocks he bought was out of one of Tommy Kendall's cars. Those bores were larger than standard and required a custom roller lifter. Luckily they had some used lifters laying around and for $1k they were his. 😲 At that level a few thousandths of roller diameter may have squeezed and extra HP or two.

The difference in initial contact point between a roller and flat does make for an interesting geometry problem especially how it changes as the cam rotates.

Lunati has a good writeup:

 

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Of the couple dozen cams I have installed I have had 2, back to back, wipe out back in the late 90s. It was for a SBC and after I did the initial break in he proceeded to run them to valve float on his way home (this guy scattered more engines than I can even count) and two days later complained of a miss. On the 3rd one I broke it in and then refused to give him his car back until I put some miles on it, but less than a month later he had sent a rod through the block.
 

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Funny I keep seeing over and over how roller lifters open a valve faster. If you look at the lobe profiles, that isn't really true. Flat tappet profile tappets can be slapped open by a lobe profile that's almost a triangle. A round roller can't ramp up that quick, it's simple geometry. The rollers do gain advantages after that initial opening though. Rumor among the turbo people is that turbos respond well to that ability of a flat tappet to get the valves cracked open quicker. For some that particular gain seems to be worth the tradeoff. But it's all pretty esoteric unless you are putting engines on a dyno or chasing tenths on a racetrack.

I wiped some lobes on a cam once. Eight years after I built it. For some reason I had a time wrapping my head around the failure at the time and kind of refused to believe that's what happened for a while. If it had happened at or right after break-in I would have thought nothing of it. But 50K miles later threw me a bit. It didn't do it again that I know of. Sold it about 10K miles later. A plain jane 1970's 302.

You mean like this:

789795

Of course, these lobes are just a sketch, but they show that flat tappet and roller lifters open in a different way. The contact point of the roller lifter is (almost) directly under it but for the flat tappet, it moves from one side to the other.
 

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So the reality is that, with a roller, the opening can be delayed. And that is probably the benefit that Ford was seeking.
 

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You mean like this:
Yes. (Nice illustration!)
But I'm hoping people were clear on how I was saying that particular part of the cam/lifter action is only an advantage to a specific type of engine and is only a small part of the cam profile. Roller cams have advantages in other parts of the cam profile if you want to wade into the deep water. I don't care to. I like both style of cam in their place.
My main motorcycle has roller lifters as part of a design package that enables it to function just fine with about 3 PSI of oil pressure when hot. Last I measured it was with 60W oil in it. I've been running 20W50 since and the pressure is probably low enough with that I don't have a gauge to read it accurately.
 

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So the reality is that, with a roller, the opening can be delayed. And that is probably the benefit that Ford was seeking.
Yes, a higher lift vs duration ratio is the big benefit of a roller. Don't get me wrong, I'm not here to prove that flat tappets are better (I have a roller cam in my 289 myself). I just wanted to show that comparing the shape of the cam lobes is not representative for the way a flat tappet cam opens.
 

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I’ll never install another flat tapper cam in anything. It’s always a roll of the dice. Even with proper procedures and break in oils etc. roller is the way to go.
 

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I know it’s a cost vs convince thing, but how many have wiped out a cam. This is assuming proper break in oil, assembly lube,and start up procedures .

Don H
Been there done that. Comp Cam with Rhodes lifters...ate the line and the bottom of the lifter. Motor was set up right, just one of those things is what I was told. Moved to roller cams/tie bar lifters and have not had it happen since. Coincidence?? I think not.
 

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I have not lost one in the dozen or so engines i have done. But back in the day ( 50s -60s) A lot of sbc would wipe a lobe after 50,000 miles i replaced a few of them.
Someone mentioned ohc engines don;t wipe cams. I had a pontiac 6cyl ohc with a bad lobe fixed it with a 389 from a 65 gto.
In hind sight I should have fixed the gto (hit in the front)and junked the 66 tempest.

Seamed like back then it was a gm problem.

ken
 

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You mean like this:

View attachment 789795
Of course, these lobes are just a sketch, but they show that flat tappet and roller lifters open in a different way. The contact point of the roller lifter is (almost) directly under it but for the flat tappet, it moves from one side to the other.
Your sketch illustrates the problem with flat tappet lifters and aggressive cam lobes. The lobe ramp angle cannot exceed the lifter “flat” such that the edge of the lifter digs into the cam lobe. That would equal instant cam/lifter destruction. Sure, the lifter will contact the lobe across its entire face as the lobe goes round and round, but if the contact patch between the cam lobe and lifter gets too small, say goodnight to the cam!

With a roller lifter, you can increase the ramp angle immensely pushing that lifter up to max lift in no time, more aggressively than you show in your sketch.

I’ve only built two motors myself... one with a flat tappet, and the second a roller. No wiped cam lobe issues for me in my limited experience. A coworker of mine wiped a cam in his youth, and it’s scarred him for life. 😁

I am wondering if there is some relationship with wiped cams and sloppy valve trains. If a hydraulic lifter isn’t adjusted right (or solid lifter for that matter), and the valve train starts to bounce, flex, or otherwise bang into the camshaft lobe uncontrollably, possibly even created by a harmonic at a certain RPM, I could see that being a cause. Unfortunately, once the cam goes flat, it’s hard to determine if the cause was related to too much or too little valve lash.
 
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