What could cause a valve to snap
- Thread starter ryan-11
- Start date
it is safe engine if you mean non interferance(sp.) engine, hard to say, any picture of the valve? any spec of the head? could be alot of things, broken spark plug, deformed/melted valve with heat, worn/damaged valve guide, bad valve seat etc.
ryan-11
Member +
The head was port and polished, cruise valve springs and speedvision cams, it was also rebuilt about 500 miles ago it also got all new valve guides.
The valve looks like it has snapped, the valve head has wrecked the head, piston and bore and ended up in the inlet manifold, the valve doesnt looked burnt and the spark plug still has the tip on it.
all this came out the head
danturbo4311
Member +
That looks nasty, whats the cam lobes & shims like, is there any signs of damage to any of the other valves, did you have the spring base pressure checked when you installed the cams & springs
Iain@CRD
Lifer
Thats friggin crazy Ryan! By looking at that id assume without checking the engine over that it would be timing belt failure but as you've said your timing was spot on.
Where the collets on the valve properly? I reckon it looks like the valve has dropped and touched the piston leading to all the failure.
Where the collets on the valve properly? I reckon it looks like the valve has dropped and touched the piston leading to all the failure.
ryan-11
Member +
the cams and shims are all fine, all the other valves look ok and yeah the spring base pressure was all checked
Yeah the head was skimmed but not sure how much was taking off, the block wasnt. yeah the plug was out just before it happened and it was fine, i only had the speedvision cams in for 6 days.
Yeah Iain i timmed it up before i took the head off and it was fine. The collets were fine.
JasonGlanza
Lifer
:S very bad
350ep70gr
Member +
Wrong installation of the valve guide..misaligment..or ported to much at the end of the valve seat and start of the runner.
Have you notice any reduction on power just 1 mile before this happends(or anything like a slight misfire)?If yes then is the second option from above..
Chris
Have you notice any reduction on power just 1 mile before this happends(or anything like a slight misfire)?If yes then is the second option from above..
Chris
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ryan-11
Member +
It just all of a sudden lost power then i heard a loud chapping noise, i pulled over to stop but before i could stop it cut out.
No it wasnt
Na dont think so cause it was running fine after i put the plugs back in
So do u not think the valve snapped and the head of the valve has been bouncing off the piston and head?
cheers for the help guys
Texx
Super Moderator
That's my thought. If the valve guide is not aligned with the valve seat or the valve seat hasn't been cut square to the valve stem/guide, it'll cause the valve stem to flex as the valve opens and closes. It won't take much of this flexing to fatigue the valve stem and eventually result in the valve head breaking away. Looking at your photos, I'd say the valve head has broken away (likely due to the above reason/s) dropped into the cylinder, been smashed around by the piston ripping the valve seat out in the process and then thrown back out into the intake port.