2006 GT broken valve again

[Waakeeen]

I broke a valve back in 2022 on cylinder 7. It has Manley valves and upgraded springs unsure about the brand but undamaged. Took the head replaced the valve and ran perfect until today. Broke cylinder number 8 this time. Both were the exhaust valves too. First time around I was thinking bad luck but to happen again on the same head there has to be something I’m missing. It’s Lito tuned forged internals Vortech supercharger pushing out 18psi. Any help would be appreciated and apologies if this has been mentioned before I tired using the search bar with no luck.

 

[Racer45]

Im no engine expert but Maybe your timing is off a little bit on the left bank.

Are the cams degreed?

Crank woodruff damaged?

Bad lifters or rockers?

Is your revs higher then the factory recommended?

 

[whitmanink]

well not for nothing,
but seeing how u have work done to that motor,,
if you got brass valve guides , some batches were found to be bad and i believe had an edge on them that would damage and worst case .,brake valves ..

not saying this is the issue,, but unless you got some crazy things going on in the cylinders (hydroloc ect) i dont see why you would be loosing valves otherwise ..

but not saying this is the problem,, but its kinda adding up

 

[GriffX]

Where does it broke? I know from my motorcycle exhaust valves can break if the lash is too big, resulting in overheating the valve shaft.
My supercharged engine has sodium filled exhaust valves to cool them down (which is remarkable that a hollow sodium filled valve is more durable than a solid one).

 

[Midlife Crises]

I am curious if there are any signs of valve to piston contact on the other pistons on that bank. Is it the head that is braking off or is the stem letting go?

 

[crjackson]

Some things to check …

Poor head gasket fitment, causing restriction of coolant flow, and localized overheating.

* Improperly machined valve guides causing alignment / seating issues, insufficient lubrication, or insufficient clearance.

 

[Juice]

Valves broke when you ran it hard?
Most likely a heat issue. Valve stem gets hot, siezes in guide, piston finishes off the valve. Post pic of broken valve.
Happened 2x, going to happen again unless you fix the root cause.

 

[Waakeeen]

I’m in the process of pulling off the head but from what I can see the valve broke at the top of the steam like the previous one did. Car ran great never over heated WOT plenty of times. It broke while I was cruising 35mph. The pics are from the last time I went through this and it’s exactly the same results except last time it was cylinder 7 vs 8 this time. I want to thank yall for the advice and info. More updates to come.

 

[Juice]

Good news: That does not look like what I said earlier, so its not heat or tune related.
Bad news:It will likely happen again on the remaining 6 cylinders. At minimum, I'd go with 8 new exhaust valves and confirm valve spring pressures.
A close up of the break could be helpful to figure out root cause.

 

[JC SSP]

Looks like the keeper comes off or loosens and the rocker/follower shears of the valve at the tip?

Reputable Machine shop should be to properly diagnose.

 

[Juice]

Why, with tip/keepers gone, the valve not fall into cylinder??

 

[Dino Dino Bambino]

Why, with tip/keepers gone, the valve not fall into cylinder??

Yeah I also noticed that. The only reason I can think of for the valve not dropping down into the cylinder and ruining the engine (a very lucky escape) is that the stem to guide clearance is too tight.
That being the case, it's likely that other valves will be similarly affected and the problem would only get worse when the engine's hot.
IMO whoever built the heads didn't do a proper job.

 

[Midlife Crises]

Wow, I’m thinking the valve guides are too tight and it’s showing up on the exhaust valves. I would definitely replace all the exhaust valves and have the guides correctly clearanced. Check the intakes as well and if they are set up like the exhaust I would be worried about stress and likely replace them also. The mystery valve springs would drive me nuts so new springs matching the cam manufactures recommendation are in order.

 

[Waakeeen]

The first time it happened I took the head to a reputable machine shop with years of experience building high hp engines. They replaced the guides and really couldn’t find a root cause. I will be replacing the exhaust valves for sure and have them double check the springs too. I’m almost done pulling the head I don’t have much time so a few hours a night after work is getting it done. The first pic is current and it’s exactly how it happened last time. The other pics are a closer shot from the valve that broke a few years ago. I have a feeling it will be the same outcome once I get the head pulled.

 

[JC SSP]

I would like to see the face of the valve (points to piston)

As stated, it might be the guides are out of spec... Remove the rest of the undamaged valve train and see if just the valve freely slides in/out of the guide... no wobble, no force, no binding or friction just smooth operation. Also, take a pic of the guide itself combustion chamber and top side just to see...

Also, check to see if the keepers are matched the valve stem grooves. Finally see if the keepers sit flush inside the spring retainer. This would be mocking the valve, keeper and retainer as if it was installed on the head... You might need an extra set of hands... LOL

I suggest another reputable machine shop... 3V operate a little different to the conventional OHV engines.

 

[Badd GT]

Valves broke when you ran it hard?
Most likely a heat issue. Valve stem gets hot, siezes in guide, piston finishes off the valve. Post pic of broken valve.
Happened 2x, going to happen again unless you fix the root cause.

I would think if stem seized in guide there would be some galling evidence that machine shop could see. Agree, without knowing if there was ptv contact difficult to remote analyze

 

[Juice]

Just noticed the S shaped valve stem. There is only one thing that bends valves....pistons. If its not heat related, the only thing left is cam timing causing PTV interference.
Still, very lucky the engine didnt do waaaay more damage.

 

[Waakeeen]

Just noticed the S shaped valve stem. There is only one thing that bends valves....pistons. If its not heat related, the only thing left is cam timing causing PTV interference.
Still, very lucky the engine didnt do waaaay more damage.

Yeah was crazy cause when the valve broke it fell and “kissed” the piston and went back into guide and got stuck. Both times I was taking a drive went on the highway went WOT as usual and drove fine until I got off the hwy normal cruising speed less than a few miles from my house the valve broke.

 

[Juice]

I had a pushrod 302 break rocker studs after hammering on it. I didnt know why at the time. I do now, it was heat/valves getting stuck.
But now you have a direction to go.

 

[Juice]

Ps: I would richen WOT by a half a point. I am assuming its in the safe range and on the lean side of safe. Is the wideband on the same side as 7&8?