I threw a shim, what happened!?!?

F

FWD-3SGTE

New member
Project with no name here!

So I took the car on the highway last night, did a 3rd gear pull and the car hit a brick wall at 7k rpm. This is what I found when I took the valve cover off...

Shim...

photo3.jpg


Cam position as is...

photo1.jpg


Cam position after I turned it a bit. Notice the bucket didn't spring back up toward the cam...

photo2.jpg


Parts are all aftermarket besides the shims and buckets. HKS cams, HKS valve springs and Ferrea valves.

Now, I'm not sure what started the chain reaction, did the cam throw a shim or did something else break which caused the shim to get tossed? Did I break a spring? Bend a valve? I'm confused. I wouldn't think that the cam would throw a shim at 7k, my cam to shim clearances were in spec as of the last time I checked so I'm not sure what happened.

I wanted to post this to hear your thoughts before I take the head off, which is a given, but still.

Thanks :)
 
4

4rsnduction

New member
Most common reason for having a shim fly off the top of the bucket is the cam lobe to shim clearance is incorrect.
The gap between the shim and the bottom of the lobe at full stroke needs to be tailored so the lobe dosnt strike too much surface area of the shim....striking a larger area helps the lobe dig into the shim, all this force causes the shim to be displaced at higher rpm.

What are your clearances for the rest of the shims ?
 
E

esracing

Member
fuck the head needs to come off to fix the bucket area of the head.most people do the under bucket style shim .what lift and deration cams 272 ,264?
 
F

FWD-3SGTE

New member
4rsnduction":h0mjr6t4 said:
Most common reason for having a shim fly off the top of the bucket is the cam lobe to shim clearance is incorrect.
The gap between the shim and the bottom of the lobe at full stroke needs to be tailored so the lobe dosnt strike too much surface area of the shim....striking a larger area helps the lobe dig into the shim, all this force causes the shim to be displaced at higher rpm.

What are your clearances for the rest of the shims ?
Click to expand...
I'll have to check the clearances over the next few days. I checked the clearances a couple of months ago because the head is a bit noisy after the build but everything was well in spec.

esracing":h0mjr6t4 said:
fuck the head needs to come off to fix the bucket area of the head.most people do the under bucket style shim .what lift and deration cams 272 ,264?
Click to expand...
If I could go back, I would do the shimless bucket conversion but didn't think it would be problem because I'm not revving overly high. Cams are 264's.

esracing":h0mjr6t4 said:
the valve mite be bent now because its not returned up al the way.
Click to expand...
That's what I'm afraid of.
 
4

4rsnduction

New member
FWD-3SGTE":3qnozwrp said:
4rsnduction":3qnozwrp said:
Most common reason for having a shim fly off the top of the bucket is the cam lobe to shim clearance is incorrect.
The gap between the shim and the bottom of the lobe at full stroke needs to be tailored so the lobe dosnt strike too much surface area of the shim....striking a larger area helps the lobe dig into the shim, all this force causes the shim to be displaced at higher rpm.

What are your clearances for the rest of the shims ?
Click to expand...
I'll have to check the clearances over the next few days. I checked the clearances a couple of months ago because the head is a bit noisy after the build but everything was well in spec.
Click to expand...

Stock clearance numbers will not apply to after market cams because the lobe profile is different, this makes the clearance gap different, an experienced machinist or head specialist will be able to get satisfactory clearances because they do it day in day out and also have the correct machinery and tools
 
F

FWD-3SGTE

New member
Gotcha.

Well, I furthered inspected, a little. I removed the intake manifold and was able to slightly peek in side the head with a mirror and it doesn't look like a valve is bent. I'm not sure when I will be pulling the head but I will keep this up to date, as best I can.
 
T

tubasteve

New member
What retainers did you use? I know Brian Crower sells two types of retainers. I spit a Sim two years ago, stock cams and head work....was 16 psi deep in third rounding a freeway clover when mine went it ten another three miles, cause i couldn't hear it. Checked shims leak down, and cam...its still running fine with longer harder pulls than that.
 
K

klue

New member
you use the stock valve clearance regardless of what cam, thats to maintain an oil film. From where it popped out I would be checking if your cam is also bent. Do you have the high lift cam? with a 264 duration keep in mind your putting alot of stress on the shim for a longer period of time, it also rolls open and closed faster than oem. Im running stock shims on gen 3 cams up to 7800 rpm no issues, on 264 up to 8,000.

my guess you had an assembly issue, or a cam issue
 
F

FWD-3SGTE

New member
I believe that I had new OEM retainers installed.

I don't know if I have the high lift cam, I just know they're HKS 264's. The shim was thrown at 7k rpm, I thought it was odd.

The whole build has less than 2k miles on it, I don't drive it much. The head was a noisy fella though, not sure why, all clearances were well within spec, maybe too tight? Idk what causes loud ticking other than faulty cam clearances, are any of your built heads noisy?
 
T

tubasteve

New member
FWD-3SGTE":1gx8hw2n said:
I believe that I had new OEM retainers installed.

I don't know if I have the high lift cam, I just know they're HKS 264's. The shim was thrown at 7k rpm, I thought it was odd.

The whole build has less than 2k miles on it, I don't drive it much. The head was a noisy fella though, not sure why, all clearances were well within spec, maybe too tight? Idk what causes loud ticking other than faulty cam clearances, are any of your built heads noisy?
Click to expand...


No, I'm uploading what i think happened. Pull the bucket out...you'll find your reason. I had a bucket float before and get wedged, turned out the bucket was out of round. I'm gong to 1zz $him le$$
 
F

FWD-3SGTE

New member
Let's say the bucket was out of round and got wedged, do you think the head is damaged by that, being "soft" aluminum and all?
 
F

FWD-3SGTE

New member
UPDATE!

I finally got the head to the machine shop. They got the valves out to inspect the cause of the incident. They found no sticky valve stems and no scoring on the valve seals, pretty much no sign of what happened. They DO think the valve must have floated for some reason and that's when the shim got tossed. Why the valve floated? Beats me. They were thinking that maybe the valve spring wasn't strong enough and didn't close fast enough, but it's all HKS and apparently they make their springs to work well with the cams.

I contacted HKS to see what they think and we'll go from there. One thing for sure is that I now have a $300 paper weight :bangshead:
 
L

l0ch0w

New member
High lift cams are well known to throw shims.

I wish I could have stumbled upon this earlier, I would have told you the procedure on how to verify if your valve was sealing properly without you having to remove your head...

HKS cams means you really should go shimless... I could search for the thread describing the physics behind why this is important, but I dont feel like digging it up right now. Just take my word for it :)

-Andrew
 
F

FWD-3SGTE

New member
Lol, will do Andrew, it's actually already in the though process :)

Now I need to dig up the part number for the shims, I'm having my machine shop jot down all of the thicknesses so I can order the correct bucket from Toyota but not sure exactly what buckets to start with :twisted:
 
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