2 bent valves??

[Patamos]

Ok so i have a stock turbo 4g63 and timing was perfect didnt jump timing. was running with walbro 255 so very rich, but ran ok. a day later the engine just stopped. groaning i tore the engine apart and found 2 broken valves and the piston was cracked in half. Is there any possible explanation for only two bent valves? thanks

 

[BogusSVO]

intake or exhaust valves?

 

[-red97rum-]

Ok so i have a stock turbo 4g63 and timing was perfect didnt jump timing. was running with walbro 255 so very rich, but ran ok. a day later the engine just stopped. groaning i tore the engine apart and found 2 broken valves and the piston was cracked in half. Is there any possible explanation for only two bent valves? thanks

Only time I've seen that happen is with a broken timing belt. That really sux either way though man, that kind of shit causes a LOT of damage. Check out your turbo too, it's likely some metal pieces made their way through the hot side. I'd say the explanation is: Those two valves were open the furthest when the timing belt let loose. It's possible the other valves made contact as well, check the valve reliefs on the other pistons for dents/marks.

 

[91TSIallday]

what if the valve guides/steams broke and gave way couldnt that cause his problem too?

 

[BogusSVO]

if the valve failed, its just age and abuse, parts wear out,

the head of the valve breaks off, and gets wedged and cracks the pistion like a coconut shell

I would guess he ran lean, for some reason or another,the extra heat, stuck the valves in the guides, leaving the valve open, the piston hit them, bending the valves and busting the piston, that would cause this and leave the T-belt in time and not broken

 

[91PRdsm]

I had that same problem(no broken pistons) but all my 16 valves. Timing belt went loose!! Did you check timing before opening the engine? or maybe did you check your the belt tension? Any way check all the valves just to make sure!

 

[Patamos]

oh sorry they were the two intake valves on number two cylinder and timing was perfect. This may have nothing to do with it but at the time i had no torque wrench so i tightened the cam caps hand tight. other than that i think i could have been aging valve springs (190000 miles on junkyard head)

 

[BogusSVO]

I have found out that most time the Valve springs need to be replaced, age and mileage.
A over rev may have caused them to hit.

 

[Patamos]

wow that was a while ago. anyways talking with my cousin who works on cars filled me in that valves are welded together. so old valves are the main source of the problem cause looking at the valves it looked like it was pulled apart.

if the valve failed, its just age and abuse, parts wear out,

the head of the valve breaks off, and gets wedged and cracks the pistion like a coconut shell

I would guess he ran lean, for some reason or another,the extra heat, stuck the valves in the guides, leaving the valve open, the piston hit them, bending the valves and busting the piston, that would cause this and leave the T-belt in time and not broken

It was also very pig rich with stock turbo injectors, 255lph and no fuel pressure regulator, with old valves. so what you said is so far the most accurate and the best diagnosis.

 

[rhodess89]

high rpms can make a valve float if they are stock springs and that is a possibility of making them wack the piston.

 

[BogusSVO]

not all valves are weled, looking at the stock ones, they look cast and machined. But a one piece valve still.

 

[Delta Cam]

op? have you pulled the rod off the crank yet?
If I had $5.00 to throw at a bet....... I bet the rod bearing spun allowing the piston to travel too far up and eat the valves.