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Here was a problem on some of the Inteks made @ 2004 or so, one of the lobes would wear down to almost round, and would cause all kind of squirrelly running problems.
Here, I put a black line @ where the lobe tip should be on this old junk cam.

Fish said:

Here was a problem on some of the Inteks made @ 2004 or so, one of the lobes would wear down to almost round, and would cause all kind of squirrelly running problems.
Here, I put a black line @ where the lobe tip should be on this old junk cam.

View attachment 53732View attachment 53733

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Too much valve spring pressure? Something in valve train on that valve hanging up and not moving free?

Have seen that issue on both the single and V twin engines. Some were caused by the valve guide moving causing valve pressure issue, but not enough to bend the push rod, and on others it was just an improper hardening of the sintered metal lobe.

Yeah, they did a cam change and the cams looked different, more of a 1 piece deal, not those pressed on lobes.

How about the cams in the Briggs & Stratton 206 Intek engine.....Steel shaft with PLASTIC pressed on gear and lobes.... and they fit into the Briggs & Stratton Motorsports "Animal" single cyl racing engine....plastic lobes does make it real easy to gain lift & or duration though also makes it real easy to screw it up too!
I've got one on them somewhere around here!

mower king said:

Too much valve spring pressure? Something in valve train on that valve hanging up and not moving free?

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Because the lower lobe was designed to be running under the oil level it was assumed that it would require less hardening so that is what it got.
Not a good engineering solution but it did save 5¢ on every cam.

mower king said:

How about the cams in the Briggs & Stratton 206 Intek engine.....Steel shaft with PLASTIC pressed on gear and lobes.... and they fit into the Briggs & Stratton Motorsports "Animal" single cyl racing engine....plastic lobes does make it real easy to gain lift & or duration though also makes it real easy to screw it up too!
I've got one on them somewhere around here!

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I have a cam from a late 70's early 80's from a 3-3.75 hp Briggs that has the plastic cam lobes and gear molded as one piece with a metal shaft pressed through the center.

Plastic cams seem to do good durability wise.

bertsmobile1 said:

Because the lower lobe was designed to be running under the oil level it was assumed that it would require less hardening so that is what it got.
Not a good engineering solution but it did save 5¢ on every cam.

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?? Note it is not always the lower cam lobe which rounded off, see pictures. I think there was simply poor hardening on a bunch of Chinese cam lobes. Going cheaper, doing away with the one pc. forged camshaft was the mistake.
Walt Conner

So far this year I had two 793880 cams with the exhaust lobes worn away. Both were from 2011 engines.

Scrubcadet10 said:

Plastic cams seem to do good durability wise.

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Yes they do but, they are not just plastic, they are Phenolic Plastic....crazy tough!

mower king said:

Yes they do but, they are not just plastic, they are Phenolic Plastic....crazy tough!

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Of course I should try telling that to a FD590 owner ,lol

Scrubcadet10 said:

Of course I should try telling that to a FD590 owner ,lol

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Yeah, no kidding....nobody thinks a plastic cam is a good idea....even people that don't know about engines knows plastic in an engine is no good!....we're not gonna tell them that their governor assy is probably plastic too...are we?

Tinkerer200 said:

?? Note it is not always the lower cam lobe which rounded off, see pictures. I think there was simply poor hardening on a bunch of Chinese cam lobes. Going cheaper, doing away with the one pc. forged camshaft was the mistake.
Walt Conner

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Interesting Walt
The only ones I have seen were lowers and because I am curious & still have some friends in the business, took one in, cut sections & did micrographs.
The depth of the hardening on the base circle , which should have not been worn was a lot thinner ( by about 1/3 ) than the other lobes, thus the assumption of deliberate less hardening.
Even more interesting was it is a powder pressing .

Bert, in my case the two I seen on Briggs single cylinder cams have both been the upper lobe (exhaust).

bertsmobile1 said:

Because the lower lobe was designed to be running under the oil level it was assumed that it would require less hardening so that is what it got.
Not a good engineering solution but it did save 5¢ on every cam.

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?? I know things are different "down under" but here in the States cam lobes do not actual run under the oil level (grin)
Walt Conner

Got a Toro in yesterday with a Kawasaki engine popping through the intake. Exhaust cam lobe on number one cylinder is almost round with very little valve lift.

It can even happen to the best of them.?