V8 Gen3 SHO death rattle - shim wearing lip of bucket

[Qshiplvr]

A few months ago, I started up the Gen3 SHO coming back from a Physical Therapy appointment, and heard the dreaded death rattle. I heard it before when my shim disintegrated, and so I knew I was on borrowed time, if not too late already. I limped it home and parked it, waiting for a time for the SHO to see the SHO doctor, JohntheSHOguy.

Got the SHO towed to John’s place, where he immediately tore into the valve cover to uncover the culprit. This is what he found:



Pictured are both exhaust valve buckets/shims on cylinder #3. Notice the squared rectangle shows how worn thin the lip of the bucket is containing the shim. This is the source of the death rattle. Fortunately we caught it before catastrophic failure. The rounded rectangle shows the “normal” wall thickness of the shim bucket wall. Has anyone ever encountered failures such as this? Anybody know what causes it?

John said that the replacement shims that are in my engine don’t have the little oil hole drilled in them (they are solid) which may starve(?) the shim of a film of oil that will keep the wear down or keep the shim “floating” so it doesn’t wear down the bucket walls.

Here is a picture of the bucket with the offending solid shim removed. The up arrow points to the worn down lip of the bucket that is missing the shim. The left pointing arrow shows the “normal” wall thickness of the shim bucket with the shim still in the bucket.





Here is the picture of the offending shim:



John is in the process of removing the exhaust camshaft and replacing the bucket and shim then reinstalling. While it’s down, we’re going for some upgrades & maintenance (front wheel bearings, Cobra R big brake upgrade).


If anyone has ever experienced this failure mode or know what causes it, please chime in! We would appreciate the collective knowledge of the hive mind!

 

[Qshiplvr]

A few months ago, I started up the Gen3 SHO coming back from a Physical Therapy appointment, and heard the dreaded death rattle. I heard it before when my shim disintegrated, and so I knew I was on borrowed time, if not too late already. I limped it home and parked it, waiting for a time for the SHO to see the SHO doctor, JohntheSHOguy.

Got the SHO towed to John’s place, where he immediately tore into the valve cover to uncover the culprit. This is what he found:

View attachment 92273

Pictured are both exhaust valve buckets/shims on cylinder #3. Notice the squared rectangle shows how worn thin the lip of the bucket is containing the shim. This is the source of the death rattle. Fortunately we caught it before catastrophic failure. The rounded rectangle shows the “normal” wall thickness of the shim bucket wall. Has anyone ever encountered failures such as this? Anybody know what causes it?

John said that the replacement shims that are in my engine don’t have the little oil hole drilled in them (they are solid) which may starve(?) the shim of a film of oil that will keep the wear down or keep the shim “floating” so it doesn’t wear down the bucket walls.

Here is a picture of the bucket with the offending solid shim removed. The up arrow points to the worn down lip of the bucket that is missing the shim. The left pointing arrow shows the “normal” wall thickness of the shim bucket with the shim still in the bucket.



View attachment 92274

Here is the picture of the offending shim:

View attachment 92275

John is in the process of removing the exhaust camshaft and replacing the bucket and shim then reinstalling. While it’s down, we’re going for some upgrades & maintenance (front wheel bearings, Cobra R big brake upgrade).


If anyone has ever experienced this failure mode or know what causes it, please chime in! We would appreciate the collective knowledge of the hive mind!

Death rattle vid

 

[toledogt]

Great write up with pictures and the video. OEM versus an aftermarket shim? Or did earlier engines use different or better ones?

 

[Qshiplvr]

I believe the solid shims are for a different application. I think JohntheSHOguy said they were motorcycle shims???

 

[E1]

Hi Guys -
Turning on the way back machine here, details may be a little imperfect, but this is what I recall.

First of all. You shot a valve shim out of that tappet bucket. This is almost always caused by excessive clearance as measured from the bottom of the lobe (round end) to the shim surface on a cold motor.
How to check valve clearance -

Checking Valve Clearance

Each original shim has a number on it, documenting thickness. Seems that Yamaha only saw fit to put holes in the actual V8 SHO shims. Shims are/were still available without the holes from your Yamaha motorcycle house.
The little hole is not for lubrication, it is so one can use a blow-gun and force air under the little devil to get it out of the bucket - Nice feature!
The V6 SHO engines are said to have similar shims, minus the holes, and are OK to use.

From what I saw in your picture, that tappet bucket sidewall is compromised and it must be replaced. I would go through the entire engine and verify valve clearances. Usually, one may play mix and match with most of their shims to get as many of the valves inside of tolerance as possible. Then you need to only buy a few (usually thicker) shims to fill in the open spaces.
Take good notes when you are playing mix and match. A micrometer and a Sharpie are your friends, too, as the size markings often wear off.

Past that, I just moved a couple weeks ago. All of my SHO engine parts are in one of 3 storage lockers, one of which is still in the Chicago area - 200 miles away.
I DO have a box of good used tappet buckets and a small coffee can full of nearly every shim available, but it will likely be weeks before I can get to them.

If you cannot obtain what you determine you need, I can eventually come up with what you need out of my supplies.

That said. This really is no big deal, nothing too hard to replace, just be extra careful to keep HEAVY tension on the camshaft when you lift it to change the tappet. If the chain tensioner 'ratchets' even one click, you'll have to pull the front engine cover to re-time the motor. I want to say that Carter - ArkanSHO - had a setup for keeping tension on that sprocket which worked good for him, but that must have been 15/20 years ago and I can't find my notes.

 

[Texas Marauder]

Tip of the day. Place the etched number on the shim face down in the bucket. It should not wear off.

 

[gamefanatic]

I had a similar problem with one of my OEM SHIMs. Its tough to find V8 shims with the release hole, but luckily I had a V8 show up in tge junk yard about that time and I took the liberty of stripping all the SHIMs and later purchasing so.e from one of the SHO Cemetaries.

I used some large vice grips and shop towels to hold the CAM position in order to perform the surgery.

Glad you caught it!

On your cobra upgrade are you replacing the brake hoses? As I recall the originals were about 1-2 short when you have the car off the wheels.

 

[Qshiplvr]

Hi Guys -
Turning on the way back machine here, details may be a little imperfect, but this is what I recall.

First of all. You shot a valve shim out of that tappet bucket. This is almost always caused by excessive clearance as measured from the bottom of the lobe (round end) to the shim surface on a cold motor.
How to check valve clearance -

Checking Valve Clearance

Each original shim has a number on it, documenting thickness. Seems that Yamaha only saw fit to put holes in the actual V8 SHO shims. Shims are/were still available without the holes from your Yamaha motorcycle house.
The little hole is not for lubrication, it is so one can use a blow-gun and force air under the little devil to get it out of the bucket - Nice feature!
The V6 SHO engines are said to have similar shims, minus the holes, and are OK to use.

From what I saw in your picture, that tappet bucket sidewall is compromised and it must be replaced. I would go through the entire engine and verify valve clearances. Usually, one may play mix and match with most of their shims to get as many of the valves inside of tolerance as possible. Then you need to only buy a few (usually thicker) shims to fill in the open spaces.
Take good notes when you are playing mix and match. A micrometer and a Sharpie are your friends, too, as the size markings often wear off.

Past that, I just moved a couple weeks ago. All of my SHO engine parts are in one of 3 storage lockers, one of which is still in the Chicago area - 200 miles away.
I DO have a box of good used tappet buckets and a small coffee can full of nearly every shim available, but it will likely be weeks before I can get to them.

If you cannot obtain what you determine you need, I can eventually come up with what you need out of my supplies.

That said. This really is no big deal, nothing too hard to replace, just be extra careful to keep HEAVY tension on the camshaft when you lift it to change the tappet. If the chain tensioner 'ratchets' even one click, you'll have to pull the front engine cover to re-time the motor. I want to say that Carter - ArkanSHO - had a setup for keeping tension on that sprocket which worked good for him, but that must have been 15/20 years ago and I can't find my notes.

John asked me to post this question when doing valve clearances:

Can anyone post any pics of how you held the cam sprocket in place in order to remove the cam without having to remove the front engine cover.

 

[Qshiplvr]

I had a similar problem with one of my OEM SHIMs. Its tough to find V8 shims with the release hole, but luckily I had a V8 show up in tge junk yard about that time and I took the liberty of stripping all the SHIMs and later purchasing so.e from one of the SHO Cemetaries.

I used some large vice grips and shop towels to hold the CAM position in order to perform the surgery.

Glad you caught it!

On your cobra upgrade are you replacing the brake hoses? As I recall the originals were about 1-2 short when you have the car off the wheels.

V8 shim links on the V8SHO site

From V8sho site:

Valve shims
https://www.v8sho.com/SHO/Valve Shims.htm

Replacement valve shims:
https://www.v8sho.com/SHO/ReplacementValveShims.htm

 

[TankII]

A fellow gave me the V8 tools for the valve train. Do you live in the Northeast?

 

[Qshiplvr]

A fellow gave me the V8 tools for the valve train. Do you live in the Northeast?

Sorry, no, but thank you very much for the thought. The SHO is in the Los Angeles area.