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Had the car out for a ride, going down the road at 35 mph and started getting a miss. Check engine light flashing on and off. Got the car home ran some tests and then proceeded to pull the valve cover to take a peek. Rocker pulled right out of the head. It looks like the metal that broke off stayed up in the head, the question is do i just go for new heads assuming I cant buy just 1 or should the motor be torn apart?
Wow...looks like a bolt was overtorqued or maybe bottomed out. Your heads don't look OE...you can buy just one, but obviously you'll want it set up identical to the other bank.
Wow...looks like a bolt was overtorqued or maybe bottomed out. Your heads don't look OE...you can buy just one, but obviously you'll want it set up identical to the other bank.
They are PRC 285cc heads Everything was torqued to spec. It has the comp trunion upgrade and the bolts that came with kit were used. Apparently they bottom out and stock bolts should have been used instead. Going to see if I can buy a single head.
Wow. Man that sucks. Those do look like stock bolts, btw. The ones that come with the Comp trunnion kit have an Allen key style head. They should’ve been torqued to only 22 ft. lbs., so even if they were bottoming out, that shouldn’t be enough to stress the threads to the point of breaking the whole rocker arm boss off like that, IMV.
Wow. Man that sucks. Those do look like stock bolts, btw. The ones that come with the Comp trunnion kit have an Allen key style head. They should’ve been torqued to only 22 ft. lbs., so even if they were bottoming out, that shouldn’t be enough to stress the threads to the point of breaking the whole rocker arm boss off like that, IMV.
If the screw was bottoming, the rocker wasn't clamped tightly into the trunnion and would have subjected the screw to bending forces. I would say that bending - not the torque on the threads - was what tore the chunk out of the head.
If the screw was bottoming, the rocker wasn't clamped tightly into the trunnion and would have subjected the screw to bending forces. I would say that bending - not the torque on the threads - was what tore the chunk out of the head.
Ouch is right! Bummer. Good thing you were only doing 35 mph!
I'd strongly consider taking advantage and consider upgrading heads and cam.
If the screw was bottoming, the rocker wasn't clamped tightly into the trunnion and would have subjected the screw to bending forces. I would say that bending - not the torque on the threads - was what tore the chunk out of the head.
That’s possible. I would think that over torquing should strip the threads long before it rips the whole rocker pedestal boss off the top of the head anyhow.
But the picture shows stock bolts which shouldn’t bottom out, according to what he’s saying in his second post.
The other thing I noticed from the picture that has me wondering is oil in the bolt hole. Now that oil probably got there after the boss ripped off, but it occurs to me that IF there was oil in the bolt hole, then the hydraulic compression of that oil when the rocker bolt was tightened could put some serious stress on the bolt boss. But, at this stage, who knows? Maybe it was a casting flaw of some kind, or bad metallurgy?
I don’t know why they didn’t just make the holes deep enough, even if they punched through into the intake ports. The GM CNC LS3 heads (and most likely many others) have some of the rocker bolt holes opened right into the intake port, and all you do with those is put some thread sealer on the rocker bolts.
EDIT: OP, did you check to see whether the trunnion is okay and isn’t binding or locked up? If that happened, then there’s a chance you could get this type of damage, if the pushrod doesn’t bend first.
That’s possible. I would think that over torquing should strip the threads long before it rips the whole rocker pedestal boss off the top of the head anyhow.
But the picture shows stock bolts which shouldn’t bottom out, according to what he’s saying in his second post.
The other thing I noticed from the picture that has me wondering is oil in the bolt hole. Now that oil probably got there after the boss ripped off, but it occurs to me that IF there was oil in the bolt hole, then the hydraulic compression of that oil when the rocker bolt was tightened could put some serious stress on the bolt boss. But, at this stage, who knows? Maybe it was a casting flaw of some kind, or bad metallurgy?
I don’t know why they didn’t just make the holes deep enough, even if they punched through into the intake ports. The GM CNC LS3 heads (and most likely many others) have some of the rocker bolt holes opened right into the intake port, and all you do with those is put some thread sealer on the rocker bolts.
EDIT: OP, did you check to see whether the trunnion is okay and isn’t binding or locked up? If that happened, then there’s a chance you could get this type of damage, if the pushrod doesn’t bend first.
I will check the trunion as soon as i get car home...I was closer to a friends place when this all went down. going to get it on a trailer this weekend and get it home.
Wow. Man that sucks. Those do look like stock bolts, btw. The ones that come with the Comp trunnion kit have an Allen key style head. They should’ve been torqued to only 22 ft. lbs., so even if they were bottoming out, that shouldn’t be enough to stress the threads to the point of breaking the whole rocker arm boss off like that, IMV.
I thought they were too but I called the guy that I got the car from and he did the build and says he used the bolts that come with the comp trunion upgrade.
Busted Head Ouch!
