Cam bearings failed yet again... please help

[doublins]

The motor came out again yesterday, which marks the third RE-rebuild since the initial stroker build and swap two years ago- so this will be my fourth stroker build. That's almost funny were it not so tragic. The first time I sunk a valve that resulted in bending a pushrod and wiping a cam lobe, the second time the shop delivered the motor with covers installed, but the front oil galley plug missing, which I figured out right away on break-in, replaced, but then found the cam bearings destroyed within a few hundred miles. I blamed the destruction of the cam bearings that time on the missing galley plug.

This time the motor has gone about 5,000 miles since the last rebuild, and I just pulled the oil pan two days ago to find the cam bearings destroyed yet again (babbit oozed out around the journals (on the load side- between 5 and 7 oclock), on bearings 1, 2, and 3. The rear bearing looks fine. There is zero valvetrain binding, and I am running totally reasonable seat pressures on ls1 springs, magnum valves, with roller rockers.

The cam lobes appear to be intact- This is the exact same cam that was in the last time the bearings wiped- but it is also the same spec cam by the same supplier that was in the first iteration of the motor, in which the cam was physically destroyed but in that case the motor went about 10,000 miles and the bearings were MINT except for embedded metal from the worn cam lobe-

I've been running the same parts setup all three times- flywheel, pistons, valves, rockers, lifters, cam, crank, etc, etc, etc- but this time I ran an HV oil pump and oil pressure (even with the bad bearings) has always been super-

The last two builds I've run Brad Penn 30w for break-in, then immediately switched to brad penn 10w30. Brad Penn oil has been one constant between the two lost sets of bearings- the first motor I simply ran 15w40 diesel oil the whole time and it seemed to like it just fine, and the bearings did not wipe.

FYI I was still running the factory spring/pin setup with a double-roller timing chain- but it's identical to the first build in which the cam bearings lived.

What gives? I'm at my wits end with this piece of junk I6. I was about to scrap it and begin an LS1 swap, but I've invested SO much time and money in this thing that I feel like I owe it to myself to legitimately try to solve this problem- I don't want to give up; it will bother me forever if I do that, and I'll never know what the problem was.

I know some of you have had similar problems, is there anyone that's figured out the actual issue with these cam bearings getting destroyed?

Please help if you can-

Thank you,
Chris

[CobraMarty]

WOW!

What year engine? What cam and specs?

[doublins]

WOW!

What year engine? What cam and specs?

Motor is a 98-

UltraDyne Racing Cams

Grind # AM6 266/272-12H

	INTAKE	EXHAUST
Duration @ .050	211	217
Duration @ .006	266	272
Lobe Lift	.2941	.3027
Gross Valve Lift	.471	.484
Timing Events for 0.050	OP -2.5 / CL 33.5	OP 44.5 / CL -7.5
Separation Angle	112 Degrees
Degree Cam	108 Degrees

Separation Angle 112 degrees
Degree Cam 108 degrees

Valve Spring Info
Spring specs-

GM Short Block, part number 3911068

O.D. - 1.241"
Pressure at installed height - 80# @ 1.70"
Solid Height - 1.15"
Avg. Rate (lbs./in) - 267
80# seat pressure + 267# x (.484 exh valve lift) = 209# open pressure.

[dwg86]

silverxj used a solid pin and found a problem with his oil pump hitting on the block (not sealing were it bolts up to the block) on his last rebuild after several cam bearing failures. So far its working good.

You said on the first build you used a spring/pin set up and the cam bearing were fine. How many miles did you run the engine on the first build before you tore it down?

[SilverXJ]

FYI I was still running the factory spring/pin setup

1) Use some form of solid pin.
2) Check for cam journal run out/bent cam
3) Makes sure journals are polished with the cam rotating clock wise as viewed from the front. This lets the grain lay down so it doesn't damage the bearings
4) Make sure the oil holes for all the cam bearings align w/ the hole in the block
5) Check for oil leaks at the pump & block interface and pickup tube http://www.jeepstrokers.com/forum/viewt ... =34&t=2671
6) Use standard assembly lube on the journals, moly cam lube on the lobes

I would call Bullet cams and see if they did anything different between the two cams. Besides a new cam and different oil did you change anything else between the one with good bearings and one with bad? What about assembly priming and lube methods? Did you have any odd sounds?

What gives? I'm at my wits end with this piece of junk I6. I was about to scrap it and begin an LS1 swap, but I've invested SO much time and money in this thing that I feel like I owe it to myself to legitimately try to solve this problem- I don't want to give up; it will bother me forever if I do that, and I'll never know what the problem was.

I know exactly how you feel.

[doublins]

silverxj used a solid pin and found a problem with his oil pump hitting on the block (not sealing were it bolts up to the block) on his last rebuild after several cam bearing failures. So far its working good.

I'm planning on the solid pin this time around- the block was milled at the mating surface because I had expressed this concern to them last time, it was a perfect fit- I had great oil pressure, even with the bearings wiped- 20-25 hot idle, 60-65 hot at speed.

You said on the first build you used a spring/pin set up and the cam bearing were fine. How many miles did you run the engine on the first build before you tore it down?

10,000 the first go around before the sunk valve.

[doublins]

1) Use some form of solid pin.

Definitely will do.

2) Check for cam journal run out/bent cam

100%- although shop claims they have done this each time- in fact the FIRST cam (the one that didn't eat the bearings) showed up with some runout out of the box (they said it must have bent slightly in shipping), and they had to straighten it. The block has been line-honed as well to ensure that the cam and crank line up perfectly straight.

3) Makes sure journals are polished with the cam rotating clock wise as viewed from the front. This lets the grain lay down so it doesn't damage the bearings

I will mention this to the shop.

4) Make sure the oil holes for all the cam bearings align w/ the hole in the block

They did when the bearings were installed- I made sure of it- we had gone over this the last time the bearings wiped- I won't know if the bearings possibly spun? until we tear the motor down.

5) Check for oil leaks at the pump & block interface and pickup tube http://www.jeepstrokers.com/forum/viewt ... =34&t=2671

This was taken care of with the first build.

6) Use standard assembly lube on the journals, moly cam lube on the lobes

Standard- this is how they've prepped it each time.

I would call Bullet cams and see if they did anything different between the two cams.

Ok, good idea.

Besides a new cam and different oil did you change anything else between the one with good bearings and one with bad?

It's a physically different head (same casting) with hardened valve seats- the first head sunk the #3 exhaust valve (badly) and they hit water when they tried to cut to put the hardened seats on that one- Since I had purchased a donor motor for the entire build, I gave them my spare (original) head for the next one. The valves, springs, retainers, rockers, etc. are all the same. I've personally checked for valve train binding, though, before and after the motor was installed- and installed a valve cover spacer to prevent the rockers from contacting the baffle in the valve cover. While I had the cover off- I had run the motor to verify that everything looked good- oil freely flowing through each rocker, pushrods spinning, etc. etc.

What about assembly priming and lube methods?

Primed on the stand all three times, very first motor used nothing but rotella T 15w40 even for breakin. The last two motors (with wiped cam bearings) I used brad penn 30w breakin oil, then brad penn 10w30 from breakin on-

Did you have any odd sounds?

Well- the last two iterations (the ones with wiped bearings) had noticeably noisier valvetrains (I attributed this to the hardened seats), and a slight vibration at 2800-3200 rpm. The entire rotating assembly was balanced, and the clutch/flywheel were balanced together and marked for assembly- I also switched to bombproof mounts with the second motor (OEM with first one), so I attributed the vibration to that?

[SilverXJ]

1) Use some form of solid pin.

Someone on here had a mushroom style machined. It has a wider base to touch the cover.

I won't know if the bearings possibly spun? until we tear the motor down.

I doubt you had a bearing spin.

I've personally checked for valve train binding, though, before and after the motor was installed- and installed a valve cover spacer to prevent the rockers from contacting the baffle in the valve cover.

Don't miss the rocker trunnion.bolt binding on the rocker body. I know with the HS adjustables that shouldn't be an issue. Also check the pushrods for binding on the head. You shouldn't have this issue as you are running LS springs, but check the springs and make sure they aren't hitting the valve covers. And of course the retainers binding on the guides/seals.

Well- the last two iterations (the ones with wiped bearings) had noticeably noisier valvetrains (I attributed this to the hardened seats), and a slight vibration at 2800-3200 rpm. The entire rotating assembly was balanced, and the clutch/flywheel were balanced together and marked for assembly- I also switched to bombproof mounts with the second motor (OEM with first one), so I attributed the vibration to that?

The vibration could definitely be from the mounts. I don't know if valve seat inserts should make the valve train noisier though. A different cam would do that, but you say the cam has the same profile. It could also be attributed to the bearings being wiper and not getting full lube to the lifters.

[doublins]

I doubt you had a bearing spin.

Yeah, ditto...

Don't miss the rocker trunnion.bolt binding on the rocker body. I know with the HS adjustables that shouldn't be an issue. Also check the pushrods for binding on the head. You shouldn't have this issue as you are running LS springs, but check the springs and make sure they aren't hitting the valve covers. And of course the retainers binding on the guides/seals.

I don't have the adjustable HS rockers, rather the ones that mount to the factory pedestals- There is no sign of any interference anywhere (i.e. marks or scratches on the anodized surface) but I will certainly put this on my list of "things that we should sanity check before buttoning up this next motor"
The rockers/springs aren't hitting the covers- Originally (first motor) a couple of the rockers had touched the baffle inside the cover, but I installed a spacer to fix this, and there was plenty of clearance.

The vibration could definitely be from the mounts. I don't know if valve seat inserts should make the valve train noisier though. A different cam would do that, but you say the cam has the same profile. It could also be attributed to the bearings being wiper and not getting full lube to the lifters.

Yeah i'm wondering if the noise was related.


So, I'm definitely going to do the solid pin, or some variation thereof- I don't know if I should have some sort of steel surface placed on/through the aluminum timing cover for the contact point of the cam button to mitigate wear on the cover? Can I machine the block to retrofit the factory retaining plate from the later motors? I.e. drill/tap holes to accept the bolts that keep it in place?

[CobraMarty]

Can I machine the block to retrofit the factory retaining plate from the later motors? I.e. drill/tap holes to accept the bolts that keep it in place?

This is a great thought and option if it can be done. I've always wondered the same thing.

[SilverXJ]

I am not sure how steel against steel would work for the pin. I was told you want to run different type of metals in a situation like that. However if you look at the the cam gears its cast against cast, similar to most of the valve train. But if you look at the Chevy style cam buttons they usually have an steel cover and run aluminum, bronze, nylon solid buttons.

You could place a bolt or something similar on the inside of the cover, seal it and thread it from the outside if you want to go steel on steel. I believe on your TJ the serpentine belt doesn't pass through the center of the timing cover so you have room to work with. I had a aircraft style fastener installed in my timing cover, then laid out plans to adapt a chevy style roller button until I realized that the serpentine belt goes right through the center of the timing cover. i was going to cut a hole in the cover, machine the our side flat, make a spacer and cap, giving the cover and extension in that area for clearance to adapt a chevy style roller button.

As for the retaining plate retrofit, can you provide a pic of the front of your block? I have seen some earlier blocks with the ears for the bolt holes, just not drilled and tapped.

[doublins]

I am not sure how steel against steel would work for the pin. I was told you want to run different type of metals in a situation like that. However if you look at the the cam gears its cast against cast, similar to most of the valve train. But if you look at the Chevy style cam buttons they usually have an steel cover and run aluminum, bronze, nylon solid buttons.

Ok, there's probably a reason they use dissimilar metals... if it's a common thing I won't worry about it- I was just worried that the steel could eat through a softer metal.

You could place a bolt or something similar on the inside of the cover, seal it and thread it from the outside if you want to go steel on steel. I believe on your TJ the serpentine belt doesn't pass through the center of the timing cover so you have room to work with. I had a aircraft style fastener installed in my timing cover, then laid out plans to adapt a chevy style roller button until I realized that the serpentine belt goes right through the center of the timing cover. i was going to cut a hole in the cover, machine the our side flat, make a spacer and cap, giving the cover and extension in that area for clearance to adapt a chevy style roller button.

I'll look into it- and I'll ask the machine shop -they said they frequently machine solid pins for the gm cams to solve cam walk

As for the retaining plate retrofit, can you provide a pic of the front of your block? I have seen some earlier blocks with the ears for the bolt holes, just not drilled and tapped.

Ok i'll do that when I get home- I'll pull the timing cover and check it out.

[shawnxj]

if you get a solid pin made i'd be interested in buying 1 just in case

[SilverXJ]

Its not a one size fits all deal. You still have to modify it for your engine to get the correct thrust.

[doublins]

So, my block does not have any bosses for a retaining plate whatsoever, it looks like a retrofit would not work.

Furthermore, there is some evidence on the timing cover of a half-semicircular groove indicating that the cam bolt has indeed made contact with the cover at some point, so I'm guessing I have indeed had some form of cam walk taking place.