Rb20Det Valves Hit Piston Marks.

[david69]

wooo hooo.Thanks Ben.video was tops.i worked out that I had to click on the switch thing on top left of box......thanks to all for the spoons.....

[GTSBoy]

As to the subject material of the photo though.....

I can't really see how you could get valve contact outside the relief on ALL the pistons. I can see how it might happen on 1 or 2, where someone has rotated the engine with no timing belt in it and contacted a valve which is a long way open. But if you made that mistake (which is not a terrible one anyway!) you'd be hard pressed to repeat it on every piston!

It could have been caused by some severe valve float at high boost pressures where the piston was rising and teh valve was hanging in the breeze......but I don't even know if that is remotely feasible. I'd suspect not.

Other than that......Anyone? Bueller? Bueller?

[david69]

Its got me stuffed.they are 0.5 oversized pistons.every piston has these marks on inlet and exhaust.had stock valve springs in the head.im only concerned as I have a recoed skimmed head to put on and I am also installing some 264 9.0mm lift cams and also heavy duty springs.i am gonna check the clearances before final installation but this is just a mystery to me.looks like it has hit maybe on 3 occasions but on every piston.valves in current head do not have any clash signs on any of them.

[D_Stirls]

What are the valves like, i would have thought that if there was enough contact to gouge the piston that the valves would have been bent?

[GTSBoy]

Might have been different valves or a different head though. Most Skyline repairs are done by dropping broken stuff on the shed floor and fitting less broken stuff from a wreck that tank slapped into a power pole.

[XKLABA]

As to the subject material of the photo though.....

I can't really see how you could get valve contact outside the relief on ALL the pistons. I can see how it might happen on 1 or 2, where someone has rotated the engine with no timing belt in it and contacted a valve which is a long way open. But if you made that mistake (which is not a terrible one anyway!) you'd be hard pressed to repeat it on every piston!

It could have been caused by some severe valve float at high boost pressures where the piston was rising and teh valve was hanging in the breeze......but I don't even know if that is remotely feasible. I'd suspect not.

Other than that......Anyone? Bueller? Bueller?

And if someone put the timing belt on in the wrong position then turned the crank around or it skipped a few teeth while running ?

[GTSBoy]

Maybe. I'd like to think that anything like that would make a bigger mess if it's going to mark every piston multiple times though.

[david69]

the valves in the current head are perfect.i imagine that someone stuffed up,realized then changed the head or the valves. I just cant understand how all the valves have touched at one point unless it was revved to the moon and all the valves valve bounced causing them all to briefly touch..could this be the only explanation.,i think cam timing would only affect one side or would it?

[david69]

im pulling the pistons out this weekend ill clean them up and post a picture of all 6 together.