Thrill of victory and the Agony of Defeat – Cam bearings destroyed. (NOT the lobes) - Page 3 - Vintage Mustang Forums
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post #31 of 89 (permalink) Old 07-16-2019, 03:21 PM
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The "true" rocker ratio on stock cast iron rockers is all over the place. Back when I was limited to running those , I made a fixture to check which ones gave the most lift . Some were as high as 1.62 ratio but most were in the 1.55-1.58 range. Stephen is right in that pushrod length itself does not give more lift. It's more like the wrong length ( and attending poor geometry) LOSES lift. In other words if you have a cam with a .305 lobe lift and a true 1.6 rocker ratio with "perfect geometry" and zero lash , you would get .488 lift at the valve retainer. IF you get less than that at the retainer , the rocker ratio is off or the geometry isn't right. Obviously valve lash changes every thing as far as actual lift at the retainer.
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post #32 of 89 (permalink) Old 07-16-2019, 03:25 PM Thread Starter
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Originally Posted by stephen_wilson View Post
The longer pushrod doesn't give you more actual lift, it just ensures that the operating angles of the rocker are correct. You still set the lash, to get more lift you would have to be holding the valve off the seat.
Of course! You are correct. I let the excitement of a possible cause cloud my thinking. Still of course need to check for binding

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post #33 of 89 (permalink) Old 07-16-2019, 03:38 PM Thread Starter
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Originally Posted by GT350HR View Post
The "true" rocker ratio on stock cast iron rockers is all over the place. Back when I was limited to running those , I made a fixture to check which ones gave the most lift . Some were as high as 1.62 ratio but most were in the 1.55-1.58 range. Stephen is right in that pushrod length itself does not give more lift. It's more like the wrong length ( and attending poor geometry) LOSES lift. In other words if you have a cam with a .305 lobe lift and a true 1.6 rocker ratio with "perfect geometry" and zero lash , you would get .488 lift at the valve retainer. IF you get less than that at the retainer , the rocker ratio is off or the geometry isn't right. Obviously valve lash changes every thing as far as actual lift at the retainer.
Randy

Makes sense. So my cam has .303 max lobe lift and my rockers are 1.6 ratio for .484 valve lift. But it makes sense that my actual lift will be less due to valve lash and/or if rocker ratio is not exactly 1.6. This tells me that i am OK on paper, meaning not exceeding the heads lift capacity of .55". Of course I should have and still need to check.

I spent a lot of time picking parts for this motor and still do not see a smoking gun.

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post #34 of 89 (permalink) Old 07-16-2019, 04:21 PM
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I remember a comment my machine shop manager said when I was discussing bearings with him on my 331 build. He said " all bearings are not created equal". When I asked he said he had found minute differences from one type or one manufacturer to another. I was only familiar with Clevite and my stroker crank mentioned running a specific Clevite bearing so I got all Clevite.



So, apparently there can be a run out issue with a cam. Any more than one thousandth and its no good. Even with a thousandth run out could that put put the journal tolerance too tight and the cam bearing ID's would then have to be reamed?



Roller cams have prompted bearing manufacturers to switch to an aluminium alloy bearing to handle the added stress, load and heat the roller cam can produce. These are less forgiving than the old babbit type bearings.



The cam journal tolerance as I read it is 2 thousandths for a stock build and 3 to 4 for a higher performance build. Since you can stack up tolerance issues from the cam bearing ID, block distortion and the cam journal run out it looks like it can be pretty easy to go too tight.



You are apparently supposed to torque down the main caps before installing the cam bearings which can create some level of distortion that can affect the cam bearing tolerances.



This is all stuff I have never even thought about. I don't have the cam bearing tool and haven't installed them myself in my few engine builds. I have always had to take a block to the shop for other things anyway so I have always had them install the cam bearings.


You may be dealing with one or the other or both a cam journal ID thing and a cam run out thing, the 2 of which created a too tight situation on the bearings.


Looking at this problem you have (like nailbender's wiped thrust bearing) has taught me some new stuff I wouldn't even have known to consider if I decide to pull my old flat tappet cam and go to a hydraulic roller which I will probably do at some point.
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post #35 of 89 (permalink) Old 07-16-2019, 07:11 PM Thread Starter
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Originally Posted by macstang View Post
I remember a comment my machine shop manager said when I was discussing bearings with him on my 331 build. He said " all bearings are not created equal". When I asked he said he had found minute differences from one type or one manufacturer to another. I was only familiar with Clevite and my stroker crank mentioned running a specific Clevite bearing so I got all Clevite.

So, apparently there can be a run out issue with a cam. Any more than one thousandth and its no good. Even with a thousandth run out could that put put the journal tolerance too tight and the cam bearing ID's would then have to be reamed?

Roller cams have prompted bearing manufacturers to switch to an aluminium alloy bearing to handle the added stress, load and heat the roller cam can produce. These are less forgiving than the old babbit type bearings.

The cam journal tolerance as I read it is 2 thousandths for a stock build and 3 to 4 for a higher performance build. Since you can stack up tolerance issues from the cam bearing ID, block distortion and the cam journal run out it looks like it can be pretty easy to go too tight.

You are apparently supposed to torque down the main caps before installing the cam bearings which can create some level of distortion that can affect the cam bearing tolerances.

This is all stuff I have never even thought about. I don't have the cam bearing tool and haven't installed them myself in my few engine builds. I have always had to take a block to the shop for other things anyway so I have always had them install the cam bearings.

You may be dealing with one or the other or both a cam journal ID thing and a cam run out thing, the 2 of which created a too tight situation on the bearings.
t.
All great points. I am going to measure/mic a bunch of stuff and see if anything jumps out at me. As for the cam bearings, I did not torque the main caps before installing the cam bearings. I read do it/don't do it, and decided to not. Again maybe a mistake. I did test the cam after I intalled the crank and torques all and it still spun freely. Freely as in by hand but all the assembly lube in there it did have some resistance, but it felt "good" to me, easy to turn.

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post #36 of 89 (permalink) Old 07-16-2019, 10:33 PM
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Looking at this problem you have (like nailbender's wiped thrust bearing) has taught me some new stuff I wouldn't even have known to consider if I decide to pull my old flat tappet cam and go to a hydraulic roller which I will probably do at some point.
Yea' half a dozen machine shops and five R&R's of the engine and sets of bearings. Although the C4 to T-5 swap has slowed down the rate of destruction I'm now at 10 thousandths on end play on the crank again and will be sliding another new thrust bearing in shortly.

A lot more goes on than 99% of the machine shops would ever be able to figure out and at that point you are on your own. I feel your pain Tallguy and good luck!
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post #37 of 89 (permalink) Old 07-17-2019, 12:39 AM
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Originally Posted by Nailbender View Post
Yea' half a dozen machine shops and five R&R's of the engine and sets of bearings. Although the C4 to T-5 swap has slowed down the rate of destruction I'm now at 10 thousandths on end play on the crank again and will be sliding another new thrust bearing in shortly.

A lot more goes on than 99% of the machine shops would ever be able to figure out and at that point you are on your own. I feel your pain Tallguy and good luck!
'




I am not a engine expert but those rods and mains bearings look like they have been run with out oil also


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post #38 of 89 (permalink) Old 07-17-2019, 01:16 AM Thread Starter
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'




I am not a engine expert but those rods and mains bearings look like they have been run with out oil also


Nick
That is why I posted those pics, as that would indicate a more systematic oiling problem.. I am not sure how the bearings typically wear. They are "dull" out of the box, and not sure if that comes off over time or not. I can tell you there was oil on the rods and mains when I took it all apart. And the crank journals look perfect.

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post #39 of 89 (permalink) Old 07-17-2019, 08:05 PM
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Have you pulled the cover off of the oil pump and checked what it looks like inside? I think that you are probably either running into a pump problem or you are missing something somewhere that helps you build oil pressure.

A stock (standard flow) Melling pump moving 10w-30 oil should give a new motor about 60 PSI cold, 45 PSI hot. My 289 is built pretty loose and made 45 PSI hot with a new pump and 10W-30 oil.

For you to go from 60PSI cold to 25PSI hot is an indicator of a problem to me. A new motor with good clearances should make a lot more pressure, and there certainly shouldn't be so much of a differential between cold and hot pressure.

If I had to guess (and this is definitely a guess), as your motor heats up things are expanding marginally and oil is also losing viscosity, so you may be looking for something that is oversized from spec. Essentially, a gap that gets too big when hot, causing a loss in oil pressure and an increase in wear.

Since your cam bearings are all trashed at the bottom of the bearing, I would then further guess that your cam bearings are too loose (oversized), and the timing chain / valve train is providing the pressure to shove the cam down towards the bottom of the motor.
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post #40 of 89 (permalink) Old 07-17-2019, 09:41 PM Thread Starter
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Originally Posted by Kelly_H View Post
Have you pulled the cover off of the oil pump and checked what it looks like inside? I think that you are probably either running into a pump problem or you are missing something somewhere that helps you build oil pressure.

A stock (standard flow) Melling pump moving 10w-30 oil should give a new motor about 60 PSI cold, 45 PSI hot. My 289 is built pretty loose and made 45 PSI hot with a new pump and 10W-30 oil.

For you to go from 60PSI cold to 25PSI hot is an indicator of a problem to me. A new motor with good clearances should make a lot more pressure, and there certainly shouldn't be so much of a differential between cold and hot pressure.

If I had to guess (and this is definitely a guess), as your motor heats up things are expanding marginally and oil is also losing viscosity, so you may be looking for something that is oversized from spec. Essentially, a gap that gets too big when hot, causing a loss in oil pressure and an increase in wear.

Since your cam bearings are all trashed at the bottom of the bearing, I would then further guess that your cam bearings are too loose (oversized), and the timing chain / valve train is providing the pressure to shove the cam down towards the bottom of the motor.

Great post, thank you! The more I have been digging and checking I come back to oiling as the probable cause. I am certain the valve train geometry is OK. The more I look at and research the main and rod bearings and as someone already pointed out here, they might have oil starvation damage as well (but I am still not sure). These are tri-metal Clevite 77 bearings and below quoted is what I found on their site. Given this coating is so thin, and stated for oxidation protection, maybe is normal for it to come off. I am contacting Mahle (Clevite) to see what they say.

"FLASH PLATING: Most tri-metal bearings use what is called “flash plating”. This is an
extremely thin layer (approx. 000030’) applied all over to provide uniform appearance and
protection from rust and oxidation in storage. The common flash plating choices are either an
alloy of lead and tin ranging from 10 to 20% tin content or pure tin. Pure tin has a more whitish
color while the lead-tin alloys are a medium gray color. Both have a satin finish."

The internals of the M68 std Melling oil pump look OK and it seems to function normally. I was starting to suspect lifter bore clearance issues but I am measuring at .002 clearance and the Ford manual states .0005-.002 desired and .005 service limit. I checked this as when I primed with the intake manifold off, I noticed oil coming out the top of the lifter bores. I did not video it unfortunately but it was more than I expected but I have no idea how much to expect.

The lifters I have from Comp Cams came in two different style orifice plate (2 sets as one was defective). The newer model put out way less oil then the older style that I had in there for break in. I am considering if this may be the "leak", but not much out there to confirm how much oil there should be. All my main and rod bearing clearances were in spec based on my machinist's checks, but also my own plastigage check on all main/rod bearings, but all were on the high side of "desired". That said, I did find the plastigage to be reasonably accurate, but I would put it at +/- .0005". Just my opinion.

I am reaching out to my machinist (it has been 3 years since he did the block) to see what he has to say. I'm not trying to place blame, just he has a lot of experience and might have an idea. Down to bare block now, kind of depressing, but we will see how it goes. I am very close to dropping it into the ocean and buying a new motor. I have way more money than time. But I want MY motor!

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post #41 of 89 (permalink) Old 07-17-2019, 10:06 PM
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It's situations like this when I think back to when my dad was plant manager at AGAP (AKA nationwide engine rebuilders/ Signa pro)in Fort Worth. They used to sell assembled long blocks and every one went on the spin tester to verify oil pressure and cam break in before it left the building. The very few engines they got back as failures were short blocks or bare long blocks(no valve train installed). 99% of them were all installer error and almost always not pre oiled. They rarely had any failures.
It's unfortunate things went the way they did and the company was sold to an investment company and it went under. With suppliers like them I never built my own engine as it cost more and you had no one else to back up the work.


One thing I almost never do is use a standard oil pump in an engine. I always use a high volume pump which basically has bigger gears or a HVHP pump in some engines but high pressure is usually not needed.

I will agree that assuming no valve train interference or way too stiff of valve springs and good fit of cam bearings that the only other conclusion is a lack of oil at the cam. Was the oil pump on tight and how about the pickup (loose/sucking air).
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post #42 of 89 (permalink) Old 07-17-2019, 10:38 PM
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"Just got done with cam break in. It was successful but not without a problem. Tough to start. Cranked for 5-10 sec a couple of times, no go. Fiddled with choke, gave it a little gas and got it started (but it seemed like I got lucky). Ran pretty good, got idle up to >2K and started the clock. All the physical gauges looked good. Around 5 minutes in I went to vary the idle and dropped a little below 2K and it died. Would not restart. Tried 3 or 4 times for 5 secs or so and no go.

Noticed some vapor coming out a hole where the choke used to be (as I took it off…broken). Bolted the choke housing back on. Still no start. Verified I did not run the carb bowl dry (it was at the proper level). Thinking now must be timing issue. I decide to cap off the distributor vacuum canister (and carb port). Now it fires right up. Get idle set, and watch and wait. Decide to check timing. 40 BTDC?? How, why? I assume some of the mechanical advance may be coming in or maybe I botched the initial timing. I adjusted to 20 BTDC and adjusted idle to compensate. Ran the additional 25 minutes (30 min total) varying RPM from 2000-2500. Water temp never exceeded 195F. Oil pressure was 60 PSI to start and levelled off at about 25-30 PSI."

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All oil galley plugs (3 front 3 rear) are installed and still in place after tear down, including the single 3/4" plug on the top rear. Yes, I did check distributor shaft to driveshaft compatibility and engagement. When I primed I got 60 PSI cold and then the same 60 PSI cold and 25 PSI or so hot at 1250 RPM. I know I had oil pressure the entire break-in, but did not monitor the 2nd day other than at start-up.
@Tallguy, I took the liberty to quote what you posted on your break-in thread. I've only done this to make sure those who are trying to help figure out what may have happened see how your break-in went and also to keep in mind that you have determined your rpm's actually varied from 1000-1250 due to the tachometer being switched incorrectly.

I'm not sure if initially running at 1000 rpm for the first 5 minutes and it dying as you were trying to idle up to 2500 rpm (actually 1250 rpm) would be a reason for such damage or not.

I do hope it helps get more suggestions to help get to the bottom of your problem.

Again, wishing you luck and hoping you find what caused the problem!

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post #43 of 89 (permalink) Old 07-17-2019, 11:34 PM Thread Starter
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"


@Tallguy, I took the liberty to quote what you posted on your break-in thread.


Allen
Thanks! I have no secrets and this is a great add to the thread. I just got off the phone with my machinist. He has no explanation and reiterated that melted cam bearings is not a usual failure. We are working out a time for him to come by to look at all the parts. May send the block back with him to double check everything and install cam bearings. I am 99% sure I did it right, but my experimentation with cam bearing installation is complete.

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post #44 of 89 (permalink) Old 07-18-2019, 12:05 AM
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From everything I have read, sounds like you did the build correctly. I don't think you had an oiling problem. First, only the cam bearings were affected. Second, oil pressure is really head pressure from the oil meeting resistance at the bearing clearances. The fact you had oil pressure indicates oil was getting to the bearings. And if getting to the main bearings, it is getting to the cam bearings, unless each passage to the 5 cam bearings is block. Worth checking but highly unlikely. The damage to the bearings suggest a pounding action. The cam journals have actually moved into the bearing material. Can't be from the timing chain being too tight because that would affect the #1 cam bearing most, but very little effect on the #5. Since damage is uniform on all 5 bearings and on the bottom side, it suggests pounding coming from above. The only thing I can think of that could pound from above would be valve spring bind. Would not take much, but as soon as the spring goes "solid", the softest metal will deform first. The softest metal would be the cam bearings. Also, breaking through the oil film could allow metal-to-metal contact, generating lots of friction heat.

I would not hesitate to recommend you try again with your engine, but play close attention to how close your valve springs come to binding with the amount of lift you have. Once your lifters pump up (assuming its a hydraulic cam), it can slightly alter how much your springs compress. Also, the longer push rods could slightly change the geometry. You could be dealing with just a few thousandths of an inch making the difference between no problem and the one you are having.

Not saying I am right, but it's the only scenario I can think of that fits the facts.
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post #45 of 89 (permalink) Old 07-18-2019, 03:31 AM
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Hi,
Just to eliminate all possibilites, you had the right cam thrust plate bolted to the block the right way? So that the gallery in the front does not spray all the oil on the chain instead of the cam bearing. Not long ago someone posted, that using the wrong plate can cause big trouble.


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