Cam bearing failure x2.. help...

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BrazilianZ28Camaro
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Re: Cam bearing failure x2.. help...

Post by BrazilianZ28Camaro »

SilverXJ wrote:
When primed oil comes up throught the rockers quickly. And its not just a trickle. My machinist thinks that is where the problem lies. However, many people run this combo and don't have issues. I compared the stock pushrod and rocker combo's holes. The stock pushrod has a .095" hole, where the ones I am using have a .088" hole. The stock rocker has a .064" hole, where the Harland Sharps I am using have a .080" hole. Another difference is that the stock hole in the rocker is offset more to the pushrod side of the rocker. I have also been through 3 sets of lifters on the 3 cams. The comp cam had the comp lifters, the Isky cam had the Johnson lifters, and the Clay Smith cam had the generic lifters that I have seen marketed under different names.

Code: Select all

Lifter         Body inlet       Pushrod seat
Comp           .098"               .079"
Johnson        .089"              .078"
OEM             .052"              .095"
My machinist recomends I go with the stock lifters. However i have a few problems with that. 1) cost, 2) where are they made, 3) it has a small hole into the body, but the hole going to the pushrod seat is the largest of the bunch. Wouldn't that have a tendancy to bleed the lifter if more oil is going out through the larger pushrod hole than the lifter can refill through the body hole?

I asked him about running a restrictor pushrod with a .040" restrictor and he agreed with that.
IMO, the text above explain the carnage...just pay atention to how the factory restricted the oil flow to top of the engine:

1- The body inlet of the OEM lifter is the restriction because it is the smallest orifice.Doesn't matter if the pushrods orifices are bigger than that.

The restriction you are thinkin to do ,already is in the factory lifters.

You should get they because you need the oil restriction at the same point of the main gallery ,otherwise th oil will scape through the valvetrain lash.

2-The stock rocker oil hole is offset for the same reason : Time the oil flow through the pushrod to increase even more the pressure at main galley.

Take care of these problems and check again the oil pressure with a drill. About the oil hole on new rockers,if it can't be modified, install a restriction into it or preferably at the pushrod end.

Hear your mechanic he is right, but I'd not groove the cam journals.

Anyway, is very strange the actual lifters are sending that much oil to the top...but...

Keep us posted about how this problem is solved;
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Re: Cam bearing failure x2.. help...

Post by SilverXJ »

Could you explain on how the lifters meter the oil? I am familar with the construction of the lifter and how it maintains preload. But its at its metering that I am lost. I see two versions of the metering disc. A 4 hole disc and then a waved solid disc. I my case it seems to pour oil out until it is near max lift. The passages in the disc and under the seat on the 4 hole disc are fairly small.. how does so much oil get through thou? I understand how it technically works, but not how it is really working.
Anyway, is very strange the actual lifters are sending that much oil to the top...but...
I think so too. Considering I haven't found an aftermarket lifter with the same hole in the body as the stock one.
Take care of these problems and check again the oil pressure with a drill.
Oil pressure via a gauge or other method? Because via the gauge its been good until it goes below 20. I can see how that happens though as the cam is riding directly or close to on the bearings limiting the flow to them.

Why would you not grove the cam journals? Personal preference, or is there some bad side effect such as losing journal area?

I will keep this forum posted as I think I have received the most help here as anywhere, even though I feel this topic is a bit basic for this forum.

I think I will look into the OEM lifters, possibly the Mopar Performance version. Probably purchase one of each and compare. I will also get push rods with a .040" restrictor because the valve train doesn't need that much oil and with the roller rockers as they are it may keep the flow to where it should be. As for the journal grooving I'll wait to hear your response. I'm also thinking of a HV oil pump as well... but not sure on that because I know the side effects of it. Loss of HP i'm not that much concerned with.. it extra wear on the distributor gear, especially in winter.
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Re: Cam bearing failure x2.. help...

Post by BrazilianZ28Camaro »

Well, I don't know all the hyd. lifters but 99% of the time , the oil is metered to the rockers simply by flow area. Generally is a horizontal disc fitted under the lifter cup. It have really small flow area at it sides, because the heated oil at high pressure will flow a considerable amount.
As the engine in question work with little oil pressure ,this becomes even more critical.

This is a pic with a "M" metering disc under the lifter cup:

Image

Yeah, your lifters would not flow too much oil to the rockers. Maybe they are a design variation of the above,but you can disassemble both the oem and aftermaket lifter and compare the metering systems. If you can post some pics here would be helpfull.

The fact is, there is too much oil flowing to the top of the engine, how you can limit the flow is the question.

A HV oil pump is a good idea, but worthless if you do not restrict the oil up top.

After restrict oil up top compare the oil pressure with a gauge to the previous reading.

I'd not groove the cam journals to stay with a good journal area and oil wedge formation.

The .040" hole pushrod , "correct" metering lifter and HV oil pump might solve your problem.

Don't forget to measure the lifter to lifter body clearance.

Don't be afraid about the HV pump HP loss and gear wear because a broken engine have zero HP and all its parts naturally will wear! :D
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Re: Cam bearing failure x2.. help...

Post by SilverXJ »

Here are a few pictures comparing OEM to various 4.0L lifters. The OEM doesn't use a disc. The push rod seat also doesn't sit inside the plunger like the others, but on top of the plunger. And the oil doesn't enter through the bottom of the push rod seat, but from its side where it looks like the body has a smaller ring. I'll have to take some more detailed pictures later because it really doesn't match any of the aftermarket lifters. The metering mechanism is completely different.

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Re: Cam bearing failure x2.. help...

Post by BrazilianZ28Camaro »

it really doesn't match any of the aftermarket lifters. The metering mechanism is completely different.
This is your number #1 enemy and might explain why that much oil is flowing away from the cam bearings.

Have you noticed the pushrod cup radius/shape is way different in all those lifters?

Have you noticed the "correct" pushrod tip pattern on the OEM lifter? But the contact pattern is not a big problem now, since the lifter does the oil metering.

Would be good if you had access to a stock engine like yours and watch the oil flow at rocker arms while the engine is at idle to have an idea.

Best thing to do is get new OEM lifters or play with the metering orifices from other lifters and watch the oil flow up top.
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Re: Cam bearing failure x2.. help...

Post by SilverXJ »

Ugh.. new OEM flat tappet hydraulic lifter is $17 for ONE. Mopar Performance has one for $10, still not much better though. I've ordered one of each to see if they are different from the old one I have here before ordering a set. For all I know they changed the design to the usual lifters.
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Re: Cam bearing failure x2.. help...

Post by robert1 »

If you had 30 lbs of oil pressure when you cranked it that would be more than enough to keep the cam bearings from wiping out. If you had this 30 lbs with whatever lifter combo, it would remain 30lbs so the lifters aren't the reason you lost oil pressure. I can't tell you what caused this, I've been building race motors for 36 years and supervised a shop where we sent out around 6,000 engines and I've never seen a motor repeatedly wipe out cam bearings. But I would guess that if you are looking for the lifters to correct this you'll still have the problem in the end.
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Re: Cam bearing failure x2.. help...

Post by SilverXJ »

BrazilianZ28Camaro wrote: Have you noticed the pushrod cup radius/shape is way different in all those lifters?
I don't think that radius is that different. I think the pushrod seat has a larger diameter and that may be making it look like a different radius. Regardless the ball and seat will still meet up at some point.
Have you noticed the "correct" pushrod tip pattern on the OEM lifter?
The OEM came from a well worn engine, the Comp only had 1000 miles on it. The rest are new.
But the contact pattern is not a big problem now, since the lifter does the oil metering.
If the lifter does 100% of the oil metering, its not working in some way. Maybe it needs a certain amount of resistance from the pushrod/rocker assembly oil flow path to do it effectively. I'm not convinced that the lifter is 100% at fault here.
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Re: Cam bearing failure x2.. help...

Post by stock z/28 »

Im certainly no expert but I would wonder just how much oil a typical cam bearing needs?

I have seen the oil restricted (like Mondello does on the Olds) to very little with no apparent problems.

I have no idea what is causing this, especially when you consider 2 different blocks as well as 2 different cams.

I have seen a similar issue along time ago on the front cam bearing on a six with a gear drive, and it was because the mounting surface for the crank gear was not concentric with the main and it would put a lot of load on the cam at a certain spot, but I think this engine uses a timming chain?
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Re: Cam bearing failure x2.. help...

Post by SilverXJ »

stock z/28 wrote:I have seen a similar issue along time ago on the front cam bearing on a six with a gear drive, and it was because the mounting surface for the crank gear was not concentric with the main and it would put a lot of load on the cam at a certain spot, but I think this engine uses a timming chain?
It does have a chain, which had 1/4" of deflection, but I only measured it TDC IIRC. If one of the gears wasn't concentric it could do that. Especially the cam gear. I'll check this on reassembly.
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Re: Cam bearing failure x2.. help...

Post by Cudafever »

The reason silverxj is a little gun shy about using a HV oil pump, is because, the "drip oiling" that the cam gear/ dist gear get, is vary low.
HV pump, + extra spring pressure will shorten the life of that gear a lot.

some have addressed this problem by tapping into the oil feed line and adding a oil squirted to the dis/cam gear.

At 5000 rpm(probably more like 4500rpm) there is no need for a HV pump that may add to his problems.

I think the best thing you can do at this time, is fix the cam bearings, assemble with out oil pan. make up a hose and bucket pick up tube, remove spark plugs(also valve cover) install started and spin it.

Hopefully it will show it ugly head.

It will take some fabbing to get the started to bolt up with out the tranny but it can be done with long bolts and spacers, and the backing plate.

With out the spark plugs in, you can spin that started for a long time with out it getting so hot you can't hold you hand on it.
The lifters are the best theory so far BUT.................i would put it back together the way you found it, and see if you can see excessive spray from there or any were else.
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Re: Cam bearing failure x2.. help...

Post by SilverXJ »

Is that you Flash?

Spring pressures don't have bearing on the cam gear though. I'm still on the fence about the HV pump though. I know a lot of people use them on the 4.0L without issue, but here have been a few gear failures. Its not the summer I am too worried about it would be those cold winter starts. I could always try a bronze distributor gear and see how that wears with an HV.
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Re: Cam bearing failure x2.. help...

Post by Cudafever »

Dooh #-o I've been found out :lol:

yeah, it me.

I thought you had it fix. How long have you been fighting this problem any ways?
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Re: Cam bearing failure x2.. help...

Post by ProPower engines »

Did not seen this mentioned before but how much cam clearance are you running??
The damage seems to be on the oppisite side of the oil feed hole. Is it possible the clearance in the bearing is not enough to allow a oil wedge to develope?? Seen that on chev 6cyl.'s where the cam clearance was not enough to allow the oil wedge to keep the cam off the bearings.Just because it spun don't mean it has enough clearance #-o

I have had to have cam journals ground lately as it seems the cam manufactures are making the lobes on the large side and not allowing for 1 piece cam bearings that install tighter.

The other thing that comes to mind is lifter alignment. Could it be they were bored in the block crooked? That would cause the bearing failure with more then stock spring pressures combined with tight clearance on the cam.

Stock clearance calls for .001-.003 on the cam journals so the said was the cam confirmed straight in a lathe by checking runout on every journal? Given that there is only 4 bearings that leaves a long way between them for flex.............
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Re: Cam bearing failure x2.. help...

Post by SilverXJ »

ProPower engines wrote:Did not seen this mentioned before but how much cam clearance are you running??
.0018-.0021", Stock clearance is .001-.003"
The damage seems to be on the oppisite side of the oil feed hole. Is it possible the clearance in the bearing is not enough to allow a oil wedge to develope?? Seen that on chev 6cyl.'s where the cam clearance was not enough to allow the oil wedge to keep the cam off the bearings.Just because it spun don't mean it has enough clearance #-o
The oil hole is about 70* clock wise from the damage, which is pretty much on the bottom of the cam tunnel. Regardless i'll be checking the clearances again.
The other thing that comes to mind is lifter alignment. Could it be they were bored in the block crooked? That would cause the bearing failure with more then stock spring pressures combined with tight clearance on the cam.
I didn't see any indication t hat would point to a crooked lifter bore to cam alignment. The pattern on the cam looks good and is offset on the cam lobe. The lifters spun freely in the bores. Beyond that I don't know how to better check lifter to cam alignment.
Stock clearance calls for .001-.003 on the cam journals so the said was the cam confirmed straight in a lathe by checking runout on every journal? Given that there is only 4 bearings that leaves a long way between them for flex.............
Yeah, we checked for run out on each journal. I don't recall the figure for that but my machinist said it was good.
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