3.6 Engine Tick

[seven30]

The exhaust rocker has an opening for oiling the exhaust cam, but on the right bank engine rotation slings oil toward the intake camshaft. Also, oil is delivered to the intake camshaft through the intake rockers. So there is actually plenty OP

And the reports mirror what you said - as well as documentation on replacement and so on. Right side it easily 10 to 1, if not more, over the left.

If anyone thinks that oil flung from a shaft isn't adequate, isn't going far, isn't very high volume, here's the bottom of the intake gasket from my 70 Javelin - those spots are where oil flung up from the camshaft several inches below hit it. This piece sits well above the block casting, the cam is below the block.

But do we agree the OP's cam bearing journel was badly scored? Can someone explain that?

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[seven30]

I figured I would follow up in here since I haven’t seen any newer threads on this topic. I had my rockers and lifters replaced this week (and spark plugs and some seals while everything was apart) and it took out my passenger intake cam as well.

Am I mistaken or does the journel appear to have suffered some damage too?

 

[ShadowsPapa]

Am I mistaken or does the journel appear to have suffered some damage too?

The problem is that the cam appears to have "stuff" on it - oil, flecks of whatever, maybe lint from a cloth. Without being able to wipe it off and look close, it's all speculation, IMO.
Is the journal scored? Or is that oil and bits from taking it apart?
There's brown spots on the lobes - what's that from? Coolant or something else on it?
The cam needs to be wiped with a lint-free cloth and pic of it straight on the journal after wiping off the oil and specs of other stuff.
Is it scored? It looks like it but then trying to get a closer look by magnifying the pic - not so sure. It's a poor angle to say definitively that it's absolutely bad. Looks like it - but I'd never advise doing or not doing something based on THAT picture.
And if it is damaged, and the others are ok, then it's just a matter of that one had a problem. It happens just like one main, one rod, or one cam bearing can go without meaning systemic issues.

 

[seven30]

No signs of oiling issues on the ones I have had apart (I have lost count of how many I have worked on in the dealership). I have said before and still believe that there are issues in the hardening of the intake camshafts. If it was a design flaw it would affect all of the Pentastar upgrade engines. I have seen failure of the low lift lobes on these engines as well, but it is incredibly rare. I have installed the coils and sensors on the old Pentastar engines and run them without the valve covers, and there is a great amount of oil being sprayed around. One of these days I may do that on a Pentastar upgrade engine just to see how much oil is pumped to the head for lubrication.

I have not seen left and right heads side by side but if the left head has the lash adjuster between the cams like the pictures of the right head, then the cam would have to spin opposite the right bank to have the same rocker/cam dymamics.

 

[ShadowsPapa]

I have not seen left and right heads side by side but if the left head has the lash adjuster between the cams like the pictures of the right head, then the cam would have to spin opposite the right bank to have the same rocker/cam dymamics.

Why?
Each valve has its own follower (rocker)
Each valve has its own lobe
Each has its own lash adjuster
The cams can spin all the same direction. What dynamics?
It's very much like a flat tappet - doesn't matter which way the cam spins if the lobe profile is ground to support it.
Think of the AMC 327 that was used in boats - they had a cam profile ground in reverse and the engine actually ran opposite of when in a car.
I guess I don't know what you are getting at - but this is a design very similar to other dual-cam engines.

All cams spin the same direction as the crankshaft like most engines.

 

[pbrevo64]

Am I mistaken or does the journel appear to have suffered some damage too?

That probably wasn’t the best picture. I snapped that picture when I picked my Jeep up, and that cam had been sitting in the trash bin for a couple days at that point so who knows what was on it.

 

[ShadowsPapa]

That probably wasn’t the best picture. I snapped that picture when I picked my Jeep up, and that cam had been sitting in the trash bin for a couple days at that point so who knows what was on it.

It shows the lobe damage quite clearly and that's the main thing.
The more I look and the more I think about it and seeing your post here - I'm betting there's just a bunch of "stuff" on it. If it was like my trash cans or scrap iron piles, there might even be coon poo on it by now. It doesn't take much DUST or other stuff to make an item like that look bad. Seeing you pulled it from trash to get the pic - I bet that explains that part.
The main thing is that hopefully it's fine now and goes on to live a long life.

 

[Charles 236]

My bet is "plenty". As long as the parts are kept wet, that's all that is needed. Even if only spray to the point of some run-off, that's plenty. They only need to keep a film of wet oil between the parts, and enough to get into the bearing area of the low lift rollers, and the valve stem area for added cooling.

The lash adjusters for the current rev of the 3.6 intakes of course has a second entry point for control of the 2-stage follower, but there has to be a lot of volume up there.

This would be more like the exhaust lash adjuster -

Looks like the exhaust lash adjuster sprays both directions - is that correct?

I have to correct myself here. On the Pentastar upgrade engines the exhaust rocker DOES spray oil to both the exhaust and intake camshafts. On the original Pentastar engines the rockers only sprayed oil onto the camshaft that that particular rocker ran on. Sorry for the misinformation.

 

[ShadowsPapa]

I have to correct myself here. On the Pentastar upgrade engines the exhaust rocker DOES spray oil to both the exhaust and intake camshafts. On the original Pentastar engines the rockers only sprayed oil onto the camshaft that that particular rocker ran on. Sorry for the misinformation.

Looking at multiple pictures of the exhaust lash adjuster and rocker/follower, it makes sense as it appears to have a hole directed at the other cam.
This means as long as there's a clean filter and good oil and no obstruction and you are carrying normal pressures it's getting thoroughly soaked.
It's the wet film that protects so as long as it's getting oil sprayed on it, it's adequate.
I believe you mentioned earlier about something to do with the hardening, treatment of the cam after being ground. Makes sense.
Also interesting was that if I recall correctly, when that right side intake cam was replaced, there was also to be a PCM flash. Hmmmmmm, profile change?

 

[Charles 236]

Looking at multiple pictures of the exhaust lash adjuster and rocker/follower, it makes sense as it appears to have a hole directed at the other cam.
This means as long as there's a clean filter and good oil and no obstruction and you are carrying normal pressures it's getting thoroughly soaked.
It's the wet film that protects so as long as it's getting oil sprayed on it, it's adequate.
I believe you mentioned earlier about something to do with the hardening, treatment of the cam after being ground. Makes sense.
Also interesting was that if I recall correctly, when that right side intake cam was replaced, there was also to be a PCM flash. Hmmmmmm, profile change?

I don't know if the profile was changed or not. I have measured oil pressure in the variable valve lift oil passage and found it to be within two psi of the pressure in the block. So if there is no blockage of the oil spray holes in the exhaust rocker, there is no reason for the intake camshaft to not be well oiled. I doubt that the oil spray hole to the intake camshaft would be blocked and yet the oil spray hole to the exhaust camshaft not be blocked. So... back to camshaft hardening. I do not believe that the high lift rocker arm fails first and then takes out the camshaft. But I know that when the camshaft fails, the rocker goes along too.

 

[seven30]

Why?
Each valve has its own follower (rocker)
Each valve has its own lobe
Each has its own lash adjuster
The cams can spin all the same direction. What dynamics?
It's very much like a flat tappet - doesn't matter which way the cam spins if the lobe profile is ground to support it.
Think of the AMC 327 that was used in boats - they had a cam profile ground in reverse and the engine actually ran opposite of when in a car.
I guess I don't know what you are getting at - but this is a design very similar to other dual-cam engines.

All cams spin the same direction as the crankshaft like most engines.

I meant the lobe to rocker pivot arrangement. If the rocker pivot is in the same place on both heads then the lobe engagement to rocker pivot is reversed between the heads. If for example, the cams rotate clockwise, the left head engages rocker at a maximal distance from the pivot. On the right head, the lobe engages rocker close to the rocker pivot point. Very different dynamcis.

 

[ShadowsPapa]

I meant the lobe to rocker pivot arrangement. If the rocker pivot is in the same place on both heads then the lobe engagement to rocker pivot is reversed between the heads. If for example, the cams rotate clockwise, the left head engages rocker at a maximal distance from the pivot. On the right head, the lobe engages rocker close to the rocker pivot point. Very different dynamcis.

The cam grind compensates. Simple. Same way they compensate for roller lifters vs. flat tappet cams in the center-cam V8.
The shape of the lobe handles it. 0 problems.
Basically if it wasn't a split pattern situation, they would simply flip the profile of the lobe.
That's because at maximum lift the lobe high spot is still "centered" between valve stem and pivot point. (well, that's grossly over-simplified because there's a rocker arm ratio involved)
It's all in the shape of the lobe. The flanks will be very different. Just having rollers on the intake follower dictates a very different profile anyway.

 

[seven30]

The cam grind compensates. Simple. Same way they compensate for roller lifters vs. flat tappet cams in the center-cam V8.
The shape of the lobe handles it. 0 problems.
Basically if it wasn't a split pattern situation, they would simply flip the profile of the lobe.
That's because at maximum lift the lobe high spot is still "centered" between valve stem and pivot point. (well, that's grossly over-simplified because there's a rocker arm ratio involved)
It's all in the shape of the lobe. The flanks will be very different. Just having rollers on the intake follower dictates a very different profile anyway.

Yes all true. The right side engagement line during acceleration is nearer the pivot and tends to have much higher contact force which the grind is trying to compensate for. Seems reasonable the right bank would start to degrade first if any marginal conditions exist.

 

[ShadowsPapa]

Yes all true. The right side engagement line during acceleration is nearer the pivot and tends to have much higher contact force which the grind is trying to compensate for. Seems reasonable the right bank would start to degrade first if any marginal conditions exist.

Then we should be seeing left bank exhaust cams fail..........
We didn't see this sort of failures on other engines prior to the VVL design.
What we saw on prior designs was the bearings in the rollers failing.
Think of the pressures on a flat tappet cam that's trying to push up on the short end of a 1.6:1 rocker arm.
The heavy valve spring has a 1.6 times advantage over the cam side, pushing up on that rocker at a big mechanical disadvantage, and the pivot is a simple ball arrangement.
Look how close the push rod is to the rocker fulcrum.

Sure these are making contact closer to the fulcrum than the valve end of the follower, but it's still the ramp that makes it happen and it's not much different than other designs of years ago.
Can't swear to it but I'd bet the cams ride positioned a bit differently over the follower or rocker based on the cam and head. In other words, if all else was exactly the same, bet the heads wouldn't swap side to side simply because of where the cams sit over the follower.
(would love to take some centerline measurements to see how the cams sit over the rockers and how far away the center of the cam is from the center of the valve for each cam, both heads.)

 

[Charles 236]

I know that the spacing between the intake and exhaust camshafts is the same on both heads.
There are 12 pins or 13 links between the timing marks on the phasers with the cams properly timed, and the secondary timing chains are interchangeable from left to right sides. The rocker arms are also interchangeable from side to side. Until the Pentastar upgrade engines came out, all 24 rockers were the same. So I don't think that there is any difference from left to right heads in valve position in regards to the camshaft position in the head.

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