Broken PAC Valve Spring
Joined: Aug 2007
Posts: 24,241
Likes: 89
From: Turnin' Wrenches Infractions: 005
here is probobly what happened
Spring snapped
pushrod pushes down on intake rocker
rocker destroyed valve guide due to no spring load
intake valve no longer closes and acts like an exhaust valve
contents go into the intake manifold
next cylinder that opens an intake valve to suck in air sucks in the valve guide
compression of cylinder #8 takes what is left of the guide and digs into the head
Spring snapped
pushrod pushes down on intake rocker
rocker destroyed valve guide due to no spring load
intake valve no longer closes and acts like an exhaust valve
contents go into the intake manifold
next cylinder that opens an intake valve to suck in air sucks in the valve guide
compression of cylinder #8 takes what is left of the guide and digs into the head
here is probobly what happened
Spring snapped
pushrod pushes down on intake rocker
rocker destroyed valve guide due to no spring load
intake valve no longer closes and acts like an exhaust valve
contents go into the intake manifold
next cylinder that opens an intake valve to suck in air sucks in the valve guide
compression of cylinder #8 takes what is left of the guide and digs into the head
Spring snapped
pushrod pushes down on intake rocker
rocker destroyed valve guide due to no spring load
intake valve no longer closes and acts like an exhaust valve
contents go into the intake manifold
next cylinder that opens an intake valve to suck in air sucks in the valve guide
compression of cylinder #8 takes what is left of the guide and digs into the head
I kind of figured that, but it just seems odd that it could make it's way back through the intake and up into the other runner like that.
yea the motor runs under alot of pressure, and most of the valve guide on the broken cylinder probably didn't make its way into the cylinder, and with the intake valve just sitting there, the down stroke of piston #8 and the upstroke of the damaged piston, it just worked out that way. pretty amazing if you think about it, just in a shitty situation.
The firing order is 1-8-7-2-6-5-4-3. Since it broke on #3 it probably floated the Valve open for a split second and shot the fragments up through the Intake Runner, then they sat flat on the plenum and by the time #8 rolled around it sucked them right into it. I have a Vic Jr on this car, so it wasnt hard for that to happen. Polymer Intake wouldbve been a little different. There were small fragments in #1, that's what lead me to pull the other Head and check. I called Mike at TEA and told him what I found and what I thought, he said to pull both and send them his way.
Fortunately it's not too hard to yank them off..Gbody FTW..
Cam is a 243/247, .621/.612, 114+3LSA.
I've seen springs made..wouldnt suprise me if a bad one comes out every now n then..prob why the warranty exists, nothing is perfect.
Thanks..wasnt trying to drag anyone down..just stating what I thought it was. I'm not really blaming anyone, just want it back up and running. 
Fortunately it's not too hard to yank them off..Gbody FTW..
that sucks man i hope they warranty all your stuff and get you up and running...as for the failure...there will always be variation in the manufacturing process no matter how good the metalurgy is. Sometimes there are just freak accidents, I know the process of making a spring is more intense than you would think and any little imperfection in the grain structure and bam you got a bad spring. I read the posts but i didnt see what size cam are you running? That piston damage doesnt look terrible i think you would be able to roll with that after a little cleanup, but in reality i would hope the warranty would compensate you somehow, my buddy dropped a valve on some brand new pistons and after light "grinding lol" it was running like a charm...good luck on gettin her back up and running
I've seen springs made..wouldnt suprise me if a bad one comes out every now n then..prob why the warranty exists, nothing is perfect.
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TECH Regular
Joined: Jul 2011
Posts: 452
Likes: 2
Which PAC part number where those springs? Did you contact PAC to see if there were any more reports ... possible bad batch?
Any chance the valve guide let go first (cracked during installation?) and caused the chain reaction?
Just goes to show that dual valve springs won't totally prevent engine damage if the outer spring fails.
Any chance the valve guide let go first (cracked during installation?) and caused the chain reaction?
Just goes to show that dual valve springs won't totally prevent engine damage if the outer spring fails.
TEA is the one that built the Heads so I was advised to send them to them and let them do the legwork..still under their warranty.
I would say this is better than dropping a Valve..this is minor damage that can be very easily cleaned on the Shortblock.
I would say this is better than dropping a Valve..this is minor damage that can be very easily cleaned on the Shortblock.
here is probobly what happened
Spring snapped
pushrod pushes down on intake rocker
rocker destroyed valve guide due to no spring load
intake valve no longer closes and acts like an exhaust valve
contents go into the intake manifold
next cylinder that opens an intake valve to suck in air sucks in the valve guide
compression of cylinder #8 takes what is left of the guide and digs into the head
Spring snapped
pushrod pushes down on intake rocker
rocker destroyed valve guide due to no spring load
intake valve no longer closes and acts like an exhaust valve
contents go into the intake manifold
next cylinder that opens an intake valve to suck in air sucks in the valve guide
compression of cylinder #8 takes what is left of the guide and digs into the head
To the OP, when fully open where is the rocker tip located in relation to the top of the valve stem?
The same thing happened to My buddy's truck. I replaced both l92 heads. What kinda heads are yours. Here's a link to my thread. https://ls1tech.com/forums/generatio...e-springs.html
I thought these were Stainless Guides..hmm.
The same thing happened to My buddy's truck. I replaced both l92 heads. What kinda heads are yours. Here's a link to my thread. https://ls1tech.com/forums/generatio...e-springs.html
Look just the same as the pics in that thread. I'll have to talk to Mike at TEA and tell him that the Guides probably have to be upgraded, more than likely ill need new Heads, still debating the bottom-end if I want to pull it and replace that one Piston. Before this failure I had a flawless 16k mile Engine.
I did not read this whole thread end to end. How many cylinders do you have problems with? Looks like pistons from cylinders 1,3, & 8 have marks from something. How many springs broke & what the damage to the other cylinders?
You saying the guide from cylinder #3 ended up in cylinder #8?
You saying the guide from cylinder #3 ended up in cylinder #8?
That is our spring. It has been a great spring really this is the only issue I have heard with it. Hopefully we will see it too so we can throw it under the microscope to see why and where it initially failed.