Heart Sick and Disgusted!!!

[jjzepplin]

So someone else built your motor?

[cbeerman]

Man that sucks, sorry to hear this Clay. About 20 years ago I had the same thing happen to my 70 big block Nova. Wound up selling the car and have regretted it ever since.

[wuzbie]

Sorry to hear this happened to you.
The positive side is you have an absolutely gorgeous truck!
I hope it works out and quickly.

[A1971Blazer]

Originally Posted by Chaparralman1974

I have been reading all of the horror stories with flat tappet cams and it really makes me mad that the quality of parts has gone so far south in the last decade or so. I have rebuilt a few small blocks in my day and never had one do this.
Clay

I never had a cam issue in any SBC that I ever built way back when.
I think you nailed it with "quality of parts has gone so far south"
I doubt I would ever build another flat tappet one ever again?

P.S. don't do anything rash but if you do...I'm interested!

[Chaparralman1974]

Originally Posted by jjzepplin

So someone else built your motor?

No, I built it myself. I am not a pro at all....but I wanted to do as much myself as possible.


Clay

[Chaparralman1974]

Ok, an update.....

First and foremost, I want to send a special thank you to Smitty (71meangreenc10) for helping talk me off the ledge with this thing last night and today. It really once again demonstrates the wonderful folks on this forum that work to help each other on these old trucks.

I went ahead and pulled off the intake to see what I was dealing with. As it turns out, I don't think that the engine ate the cam after all. The intake and exhaust lifters seem to look ok to me and I stuck a borescope down into the lifter bores and the cam seems to look good as well. The lobes are still "pointy" like a cam should be and don't seem to show any excessive wear that my untrained eye can see anyway.

Number 2 exhaust's rocker was cockeyed on the valve and it looks like it roughed up the top of the valve stem just a little bit. I also noticed that the push rod was bent. Not like a pretzel or anything, but it is definitely bent. Number 2 intake rocker was way loose and flopping around. I am not sure if the nut backed off or what but it was loose. I still had to use a ratchet to remove the nut, but I am not sure if it worked itself loose or not.

Both of the lifters seem to look ok with no gouging or anything. The rockers seem to exhibit a bit of wear on them though where they contact the valves.

As a good measure, my plan is just to replace all the rockers and pushrods. I will also be inspecting each of the lifters one at a time (ensuring that I don't mix them up) to make sure that they look ok and that they are spinning properly in the bores. I will then redo the valve lash and see if that fixes this.

Here are a few pictures of what I found.

Clay

[Chaparralman1974]

Here are some more pics.

[Chaparralman1974]

And more...

[71meangreenc10]

No worries Clay.

I think you should be ok if you get the parts we discussed. I can relay that some of the new rocker arm nuts are straight garbage and will back off. It is a crapshoot these days...

Smitty

[HO455]

That's got to be a relief. Glad to hear it wasn't the cam. I would take some time and verify the rockers are riding on the top to the valves correctly before ordering new push rods. Just in case you need a different length push rod.

[Chaparralman1974]

I am just trying to figure out what happened. I can’t tell if the nut backed off or what.

Clay

[weq92f]

.

This is positive news...certainly better than glitter in the pan!

Good deal!

-Kevin

[Chaparralman1974]

So, I have been reading about all the issues with the "silver" jamb nuts used on the new rockers. These are a bit pricey, but would they be worth the expense? I don't mind dropping a few bucks to ensure that this doesn't happen again, but not sure if this is over kill. I think I really dodged a bullet here (fingers crossed) so I would rather spend $177 on nuts vs. a rebuild that would cost several thousand....

https://www.summitracing.com/parts/p...DMUKsiOMFSLdXl


Clay

[57taskforce]

Check the piston with a bore scope and make sure the piston didn’t hit the valve(s). Those pushrods tell a lot. I’d bet the valves and piston became intimately connected.
You can smack the valves with a dead blow and see if they return to full closed.

[Chaparralman1974]

Originally Posted by 57taskforce

Check the piston with a bore scope and make sure the piston didn’t hit the valve(s).

That's a good idea Tyler! I will stick the borescope down the spark plug hole and take a look see.



Clay

[HO455]

Originally Posted by Chaparralman1974

I am just trying to figure out what happened. I can’t tell if the nut backed off or what.

Clay

If you have a beam torque wrench you could use it to remove the rest of the rocker nuts while watching the pointer to see if the torque is consistent on the nuts when you remove them. If you see lots of variations in the torque I would be suspicious of the nuts.

I didn't find any real smoking gun when mine failed but, after talking to a local machinist that I trust his opinion was that the rockers and rocker balls had too much wear and no longer kept the proper geometry and as a result the rockers were twisted and cocked on the studs. That in turn created friction and heat in the rockers. Which "MIGHT" have allowed a nut to loosen up.

I installed new rockers, pushrods and ARP nuts and things have been fine for some 60k miles now. I hope you have the same outcome as I did.

[Chaparralman1974]

Originally Posted by HO455

If you have a beam torque wrench you could use it to remove the rest of the rocker nuts while watching the pointer to see if the torque is consistent on the nuts when you remove them. If you see lots of variations in the torque I would be suspicious of the nuts.

I didn't find any real smoking gun when mine failed but, after talking to a local machinist that I trust his opinion was that the rockers and rocker balls had too much wear and no longer kept the proper geometry and as a result the rockers were twisted and cocked on the studs. That in turn created friction and heat in the rockers. Which "MIGHT" have allowed a nut to loosen up.

I installed new rockers, pushrods and ARP nuts and things have been fine for some 60k miles now. I hope you have the same outcome as I did.

This seems reasonable.....the rockers and ball washers are original to the engine. I think it is possible that excessive wear caused the issue.

Regardless, I have new melling rockers that I picked up today at Oreilly's. They came with new ball washers and the silver nuts. I am contemplating alternatives for the nuts just to be on the safe side.


Clay

[basketcase]

Just as a point of curiosity, on the cylinder in question you seem to have 6 threads showing on the stud above the nut on the exhaust valve (bent pushrod) and only 4 on the intake (loose rocker) whereas on the neighboring cylinder they both show 5 threads. Could it be that you were not on the base circle of the lobes when you adjusted these two rocker arms? For a pushrod to bend, something has to contact something else that refuses to move. Valve to piston clearance is usually the first thing that comes to mind, but you only had the problem on one cylinder. Another thing, if that exhaust valve was overtightened, is coil bind. If the rocker is still pushing the valve open when all of the valve spring coils collapse against each other, something has to give. That would be the pushrod. A third scenario could be that the exhaust stud was already pulled some, like press in studs will do at times. Then, even though you set the valve preload right, the stud continued to pull as the new engine ran and eventually got loose enough to allow the pushrod to pop out of the rocker arm cup and jam up on the next revolution of the cam lobe, bending it. Any way you look at it, something happened and you need to figure out what. Just re-assembling it with new parts exactly as before only puts you back where you were before the failure and doesn't address the cause of the failure leaving the door open for a repeat occurrence. Remove both rockers on that cylinder and measure the installed height of those two studs. If the exhaust stud is taller, you have a stud pulling. You can repair it with a screw in stud. If it's the same, it was overtightened.

Also install new nuts.

Tom

[Steeveedee]

Might be my old eyes, but the first lifter pictured looks a bit rough on the face.

[Chaparralman1974]

Originally Posted by basketcase

Just as a point of curiosity, on the cylinder in question you seem to have 6 threads showing on the stud above the nut on the exhaust valve (bent pushrod) and only 4 on the intake (loose rocker) whereas on the neighboring cylinder they both show 5 threads. Could it be that you were not on the base circle of the lobes when you adjusted these two rocker arms? For a pushrod to bend, something has to contact something else that refuses to move. Valve to piston clearance is usually the first thing that comes to mind, but you only had the problem on one cylinder. Another thing, if that exhaust valve was overtightened, is coil bind. If the rocker is still pushing the valve open when all of the valve spring coils collapse against each other, something has to give. That would be the pushrod. A third scenario could be that the exhaust stud was already pulled some, like press in studs will do at times. Then, even though you set the valve preload right, the stud continued to pull as the new engine ran and eventually got loose enough to allow the pushrod to pop out of the rocker arm cup and jam up on the next revolution of the cam lobe, bending it. Any way you look at it, something happened and you need to figure out what. Just re-assembling it with new parts exactly as before only puts you back where you were before the failure and doesn't address the cause of the failure leaving the door open for a repeat occurrence. Remove both rockers on that cylinder and measure the installed height of those two studs. If the exhaust stud is taller, you have a stud pulling. You can repair it with a screw in stud. If it's the same, it was overtightened.

Also install new nuts.

Tom

Hi Tom,

It is entirely possible that I didn't have the cam in the right place when I originally set the valve lash. I will be removing all of the rockers and measuring the height of the studs. They are all screw in studs that I had the machine shop do when I had the heads rebuilt, but I will be checking for sure.

And I will be installing new nuts for sure. I counted the threads as well and something isn't mathing.....I am really wondering if the nut backed off. These are the original rockers, washers, and nuts to the motor (1968) so it is entirely conceivable that they are just no good.


Clay

[Chaparralman1974]

Originally Posted by Steeveedee

Might be my old eyes, but the first lifter pictured looks a bit rough on the face.

Smitty noticed that as well when I spoke to him. I am going to take those lifters down to an engine machine shop to see if I can get them to give me some professional advice.


Clay

[57taskforce]

When you get it back together run the valves with the engine running at a slowish idle. You can cut the centers out of an old pair of valve covers to catch most of the oil slinging off the rockers and still allow adjustment. Back each rocker nut off just till it starts to rattle then retighten the nut about 1/2 turn. It’s not as easy to set the lifter preload on hydraulic lifters with the engine off/lifters bled down, as it is lash with solid lifters. This will rule out having any of them tight enough to coil bind. The thing is that if it was that tight you would most likely have known because it should have been popping out the exhaust or intake. This is because most of the time if it’s tight enough to coil bind, the excessive lifter preload won’t allow the valve to close all the way. It likely may not be open enough to hit the piston in this case as well.

[D.B]

Originally Posted by Chaparralman1974

Hi Tom,

It is entirely possible that I didn't have the cam in the right place when I originally set the valve lash. I will be removing all of the rockers and measuring the height of the studs. They are all screw in studs that I had the machine shop do when I had the heads rebuilt, but I will be checking for sure.

And I will be installing new nuts for sure. I counted the threads as well and something isn't mathing.....I am really wondering if the nut backed off. These are the original rockers, washers, and nuts to the motor (1968) so it is entirely conceivable that they are just no good.


Clay

The studs do not look like the screw in design to me. I have only seen them with a hex base and these are straight base. Nor do they have a socket head for an allen wrench. But I could be wrong. If these are screw in studs, I wonder how they got them in the head.

[Chaparralman1974]

Originally Posted by D.B

The studs do not look like the screw in design to me. I have only seen them with a hex base and these are straight base. Nor do they have a socket head for an allen wrench. But I could be wrong. If these are screw in studs, I wonder how they got them in the head.

You are correct.....I first thought that they were screwed in, but yeah, you are right these are pressed in.


Clay

[57taskforce]

Originally Posted by D.B

The studs do not look like the screw in design to me. I have only seen them with a hex base and these are straight base. Nor do they have a socket head for an allen wrench. But I could be wrong. If these are screw in studs, I wonder how they got them in the head.

Pipe wrench those aren’t screw in studs for sure. I was thinking the same thing earlier.