ok so i am in the process of putting my new rebulid head on. we put everything on right, torque everything to the b18c specs. did the whole timming on right the pistons up and dead center and the cams up and the car will start up right and sounds good but we leave it on for about 10 mins and hear a loud clank and the car turns off. We took of the valve cover and it happened for the second time the cams or off. we move the pulley so one of the cams will say up and the other one is clear upside down. It happened twice already the cams keep messing up the timming. when we first took off the head we looked at the pistons and they didnt look bent at all. But my mechanic and I are hoping its not bent rods. if you guys have any suggestions please it would help./???? dont know what else to do and i dont really want to buy a new engine.

 

If the valves are hitting the pistons, it is most likely that the valve stems are the part that gives first. It's also possible that the valve guides are cracked if the stems bend enough.

Evidence of this is minimal sometimes, but if so you should be able to see curved marks where the valves contacted the top of the piston. It may only be enough to scuff the deposits on top - not really carving metal or anything.

As for the cause, it depends upon the work done to the engine...

Have you:

Shaved the head or deck?
Used aftermarket or non-stock pistons?
Altered the valves (oversized)?
Used a cam with added lift or altered timing specs?
Changed rod length?
Used any other non-stock components or changed the physical dimensions of them?
Used any other component not installed in this engine from the factory (e.g. B16 heads, CTR pistons, ITR cams, etc)?

Give us as much information as you can regarding what's gone into this engine, and we may be able to help identify the area to focus upon...

Good luck - Mark

 

Well the head got a valve job done at the machine shop. I took it off because one of the pistons had no compression at all and saw that one of the intake or exhaust i forgot had a big hole on that piston. nothing else has been done to the engine except the head valve job. thanks

 

So, everything's stock, including the cam gears?

Was the hole from running too hot, or did the valves go through the piston the hard way?

Still need help, or ?

 

yes everything is stock.
I think it happened from running to hot i was in high rpms and then my car just gave out and thats when i took of the head and saw that the piston which had no compression at all had a valve with a hole. I talked to another guy and he said that the timing belt tensioner might be the problem.. i still dont know what to do.

 

Have you mis shifted at all?