engine knock on a '74 eldorado 500

[andysarcade]

hi all.

A bit of background : I bought the car last year, purchased as 'rebuilt engine' along with much other work done.

Its always had a 'knock' sound in the engine, it sounds like its coming from number 8, but it is not definitive. Opening the rocker covers and removing the entire rocker shaft has shown no visible wear anywhere, the parts inside there look like new and its spotless. (we're not sure when the rebuild happened, maybe up to 10 years ago? but its done very few miles since).

We checked with a .006 feeler gauge on top of the valves while it was idling to see if the it changes the noise but it doesn't. The knock sounds like its coming from lower down in the engine to be honest, but at the back, toward the number 8 position.

The knock is most noticeable at low revs, but its always there, no matter if the engine is pulling up hill, coasting downhill. It does not appear to affect engine performance at all. There is no smoke from this engine either. The only anomoly we found was that the 4 rocker shaft supports had a washer between the head and the support. The service manual shows a retaining clip affair that hold the rockers in place on the shaft, but this modern replacmeent has nylon pins preventing the rockers moving along so this is not needed. Looks like the rebuilder just threw in some washers to make up for the unusued spacer/retainer. They did not use the same thickness washers (!) so we corrected that, but with no change after we re-assembled and did a long test drive.

We are going to remove the washers completely today i think and retry (the hydraulic lifters should take up any slack anyway ad should not need this extra space). We think we've eliminated any valvetrain issues with this knock problem, but going deeper in the engine is a tougher prospect. W are surprised by how loosely the rockers sit on the rocker shaft, but they all seem to come together ok and engine runs sweet otherwise. The oil supply is perfect, no blockages and free flows up the pushrods at the right rate from each position.

Are there any engine gurus that might have any insight on this? or is it just to be expected that a knocking noise is 'usual' for these large old engines as some people have told me?

thanks!

[Scot Minesinger]

The RWD Cadillacs can have the oil pan removed for inspection underneath at bottom of engine with exhaust Y pipe and center link removal, but unfortunately the Eldorado has to have the engine pulled to do this.

Guessing you have checked timing and all that.

["Cadillac Kid" Greg Surfas 15364]

Andrew,
Just so we can all start off on the same foot, # 8 cylinder would be the rear most on the driver side of the car. Secondly stock rockers consist of (on each side) 4 individual T" stands with the rockers each fitting on one side of the tee and the retaining clip that runs under the stand, holding them in place horizontally.  What you describe  ("entire rocker shaft") seems to describe an after market shaft rocker system typically used in high performance cam installations.
It might be helpful to post a picture of the valve train.
All that said diagnosing a noise on line with no audio (you might post a u tube shot) is sort of like eating lunch off a cook book page.
If you can get a length of say 3/8 or 1/2 inch tubing and use it as a stethoscope to "poke around" in the area you suspect the noise you might be able to find the exact spot.  In the area you describe (rear of drivers side) exhaust leaks are common and they CAN sound like a knock on these motors.
Greg Surfas

[Dave Shepherd]

If you disconnect the plug wire does the noise change?

[andysarcade]

The RWD Cadillacs can have the oil pan removed for inspection underneath at bottom of engine with exhaust Y pipe and center link removal, but unfortunately the Eldorado has to have the engine pulled to do this.

Guessing you have checked timing and all that.

Yeh, would be nice to just get in at the bottom, but - Eldorado :\
We have not checked timing yet because it runs so nice otherwise, but i know what you mean - but it isn't an ignition knock. We will for good measure look at the timing this morning just to cross it off the list anyway. We know its not rod knock either from other behaviour. thanks!

[andysarcade]

Here is the rocker cover off... I will make a video of the clanking noise in a short while!

[andysarcade]

And here's the rockers.. (ignore the numbering - that was for something else)

[andysarcade]

And with the rockers off the top.

[andysarcade]

Andrew,
Just so we can all start off on the same foot, # 8 cylinder would be the rear most on the driver side of the car. Secondly stock rockers consist of (on each side) 4 individual T" stands with the rockers each fitting on one side of the tee and the retaining clip that runs under the stand, holding them in place horizontally.  What you describe  ("entire rocker shaft") seems to describe an after market shaft rocker system typically used in high performance cam installations.
It might be helpful to post a picture of the valve train.
All that said diagnosing a noise on line with no audio (you might post a u tube shot) is sort of like eating lunch off a cook book page.
If you can get a length of say 3/8 or 1/2 inch tubing and use it as a stethoscope to "poke around" in the area you suspect the noise you might be able to find the exact spot.  In the area you describe (rear of drivers side) exhaust leaks are common and they CAN sound like a knock on these motors.
Greg Surfas

Yes, just as you describe, #8 rear most driver side. My rockers are not stock, definitely aftermarket from a rebuild, but not competition i would say. We did the long screwdriver trick to listen when assembled but it doesn't definitely point to an individual cylinder. And when run with the rocker cover off, you can see its not the rockers clacking. It seems deeper. We were thinking a camshaft issue, but looking at the rest of this engine, its unlikely they would have not replaced all that too, as it looks to have had carb and transmission rebuilt too.

[andysarcade]

https://youtu.be/0kDXhfT3_10

Here's a video of the noise, i go to the passenger side first where its fine, then go round to the driver side, where its most noticeable.

thoughts?

[Jeff Rosansky CLC #28373]

Slow down for a minute. Please let me tell you about my experience. I am long winded so I will try to be brief. I have a 70. The rockers are different with the pedistal assembly but this may apply. I had a similar noise and absolutely chased my tail trying to figure it out. Check the slop on the rocker wiggle it right left, etc. I had brand new rockers and pedistals but they were all sloppy. My rockers could pivot about 10 degrees each way which also allowed them to lift on the pedistal. Made the same basic noise. I found it by running the engine with valve cover off--messy so get ready for it. I used a gloved hand to hold each rocker as it was moving. Found that if I held it on place, which took up the slop, that he noise went away.
Good luck.
Jeff

["Cadillac Kid" Greg Surfas 15364]

Andrew,
What I hear seems to be a combination of noise from the non stock rocker arm set up and an exhaust leak. It is possible that the camshaft is not stock so they added the up scale rocker system. They can be noisy. 
I would now pull the sheet metal covering the left side exhaust manifold and check the manifold for cracks.  Then IO would be sure the exhaust manifold to exhaust pipe connection is not leaking. It is common for them to not be reinstalled correctly and since there is no gasket if not perfectly aligned they will leak.
By the way thanks for the pictures and the u-tube.  It sure can help.
Greg Surfas

[andysarcade]

[another video below]

Just another bit of background, i'm working on this with my dad who has 40 years working on vintage/classic cars (albeit Europen) he's staying with me for two weeks (over from the uk) to help me work this out. He's fairly stumped considering what we've done so far. He ran 70's american cars in the uk in the 70's so is at least familiar with the big old stuff.

Jeff - thanks for that, yes - this rocker shaft kit has an amazing amount of play in all rockers that seems to be normal for it. My dad is shocked at the sloppiness having never seen this in any engine he's worked on before, but it all seems to be taken up when hydraulic pressure comes up. We put a feeler gauge in to check for the gap on the rocker to valve top (as detailed in the factory service manual) and there is no slack or room to get it in there when running, so the noise can't be from that. The rockers themselves have so much play in them, we do now wonder if there's some sort of rocker to rocker shaft noise.. it just doesn't sound like it when you're right up close. We will probe the rocker when running now too to check if it can be perceived.

Greg - We will check, but we're pretty sure there's not a manifold leak. It may be this aftermarket rocker arm :\

Here's another video if the rockers running, it is discernible the knock from front to back in the video at least too, but its not metallic enouh of a clank to zero in on a rocker itself.. its so weird.

Our new theory is the previous owner sent this in to be looked at by someone who replaced the whole rocker shaft trying to find the knock noise. The entire engine may not have been rebuilt, maybe just this side? who knows. The previous owner is deceased so its history is a closed box to us.

thanks for your feedback guys, it really helps!

here's the running with cover off:

https://youtu.be/K5Wow50PYLU

["Cadillac Kid" Greg Surfas 15364]

Andrew,the noise you have,
It DOES sound like valve train noise. Are you saying that the passenger side of the motor does not have the shaft rockers?
This noise, if you have eliminated any possibility of exhaust noise, seems valve train related. The spacers under the pedestal would indicate that they were trying to adjust the lifter pre-load.  If that were too loose, you would get lifter noise.  If the engine EWAS rebuilt and the cam not broken in properly and/if this is a high performance camshaft, the noise is the result of any of the above.
Since any in depth investigation will require possibly pulling the motor, my suggestion is to "live" with it.  If it gets louder you will be able to pin point it easier and it probably won't require any more work than you would have to get into now.
PS on my '76 when I put the motor in I misaligned the left side header pipe and it sounded much like the noise you have there.    being lazy I took about 7 years until I finally got around to correcting the pipe and the noise went away. That's me.
Greg Surfas

[Jeff Rosansky CLC #28373]

If I may again.
There may be no gap per se on the rocker. But what about the rocker arm.
May I suggest you see if the rocker moves UP as the valve opens. If the hole in the rocker that the shaft goes thru is out of round that may happen. The pushrod pushes up and the valve end is on the valve so the rocker moves UP against the pressure. I am probably not describing this well enough.
Have the valves closed and rotate the engine by hand until the valves start to open. Just before they do look for movement in the rocker.
Again I have the older design but when I loaded up the rocker arms on mine I could see them move UP before the valve started to open.
Jeff

[andysarcade]

Andrew,the noise you have,
It DOES sound like valve train noise. Are you saying that the passenger side of the motor does not have the shaft rockers?
This noise, if you have eliminated any possibility of exhaust noise, seems valve train related. The spacers under the pedestal would indicate that they were trying to adjust the lifter pre-load.  If that were too loose, you would get lifter noise.  If the engine EWAS rebuilt and the cam not broken in properly and/if this is a high performance camshaft, the noise is the result of any of the above.
Since any in depth investigation will require possibly pulling the motor, my suggestion is to "live" with it.  If it gets louder you will be able to pin point it easier and it probably won't require any more work than you would have to get into now.
PS on my '76 when I put the motor in I misaligned the left side header pipe and it sounded much like the noise you have there.    being lazy I took about 7 years until I finally got around to correcting the pipe and the noise went away. That's me.
Greg Surfas

hi Greg,

On the ground in person, getting your face right up to these, it does not sound like the noise is with the valvetrain, strange as it may seem! We have tried holding or pushing on the rockers to see if the noise will be soaked up or change and it just doesn't.. and the clank we can hear still seems to be lower down. This could of course all be a delusion because this is an entire shaft and something it transmitting along the length or causing clacks to travel. We have not opened up the passenger side rocker - because it sounds fine and i would be shocked if it was not replaced like for like. Also a little trickier to get to with AC stuff to have to move etc.. Upon further inspection we do see that the whole engine has been out for the rebuild so i'm eliminating a half-job as a possibility.

We removed the spacers altogether now, which will change the lifter pre-load agreed, but it seems to run fine without them with no difference in noise (your thoughts on this?). We will test drive in a short while. I know OEM would have the spacer and retaining clip to keep the rockers in position originally so there should have been some gap, but it looks like this takes up without problems. The rockers are tighter on the shaft than they were before, but not by much, there's still angular wiggle even when not engaged, but never a gap to the valve spring.

This rocker shaft looks to be a cheap thing, i doubt the camshaft was changed for a performance version if they went with a cheap slack rocker kit, but who knows. My dad is convinced an exhaust issue cannot be the case - but i'm deferring to checking everything while we can, so we're checking for that next!

Ultimately i think i'm going to change the rocker setup for something nice, or even back to stock if i can find some good used spares, to eliminate a drive train noise issue as i know this is sounding like the more i provide videos!

Here is a video showing the play in the rockers on the shaft when removed, its pretty impressive and my dad being a mechanical engineer is horrified this is 'normal' or that the engine runs as nice as it does like this!  :

https://youtu.be/YJIADSoGaS4

Or - as some have already said - Live with it until it changes or becomes more 'diagnostic'. My main reason to dig deep on this is that i want to ultimately tow with this vehicle after i do some necessary tow package upgrades, and i want to know i can depend on the engine.

OH! another big issue we have, how to you turn the crank on the engine on these? the fan is viscous and we can't see anywhere to turn the crank by hand??!?

thanks!

[Jeff Rosansky CLC #28373]

That's the gap I was talking about. Approx 2 seconds in yiu can see the gap between the shaft and the hole in the arm. I bet as you rotate the engine by hand and bring the rockers from an unloaded position to loaded you will see the rockers physically move up a 16th or so. That was the noise on mine.
On the 472 you can insert a fine threaded 9/16 bolt onto the oulley. I think 500 is the same but not sure. They had a cork plug in the hole but if it was rebuilt I would think it isnt there.
Jeff

[andysarcade]

aaaand this is why that even though i love my dad, its worth being thorough in investigations when getting great suggestions from people on this forum

Found a manifold crack on the driver side... although a source of our clanking noises it is not...

We are starting to think that the rocker kit put on this engine just is not of great quality - it may have worn imperceptibly too, but it may be the source of our clacking and the only way to know is to change it out... But for now it just runs, so when i'm feeling adventurous i might leave replacing it until then. I will of course try to replace the manifold as soon as i can as well to improve/eliminate that too.

Jeff - it seems od that an otherwise new looking engine rebuild is 'worn' like this, maybe just made bad?

I think we're done for this mornings work!

Where is the best place to get new rocker kits, just caddy daddy?

[Jeff Rosansky CLC #28373]

This thread (if I am doing it right) may explain a little better. I actually just reused my old parts.
http://forums.cadillaclasalleclub.org/index.php?topic=143600.msg351510#msg351510

["Cadillac Kid" Greg Surfas 15364]

Andrew
Before you do anything else I would suggest you replace that exhaust manifold.   
If you can’t find one at MTS or A&A in Brentwood CA PM me I believe I have one I took off an engine that was excellent. Same thing if you ever get go back to stock on rocker set up

Greg Surfas