is this due to detonation or something else.....chewed up pistons look

[cunic]

what the heck could have cause this?

[clss240]

detonation doesnt cause that. at the lower portion of the pic it looks like valve contact that bigger mark at the top looks like something got in there. maybe through the intake or spark plug hole during plug change i dont know but doesnt look like detonation.

[480sx]

The two marks on the bottom of the piston is defiantly valve to piston contact. The other mark is from some contact directly with the piston.

DEF not detonation..

[Vegascorbin]

What was the reasion you pulled the head? May give you a clue. Definetly something either got in the cylinder or the piston traveled up and out of the block and it hit the spark plug.

Side note: Does anybody have a good picture of what damage from detonation WOULD look like?

[redtop91]

The two marks on the bottom of the piston is defiantly valve to piston contact. The other mark is from some contact directly with the piston.

DEF not detonation..

Seconded. Timing chain eff up? Or maybe valve float? Detonation damage manifests itself in cracked or deformed piston domes. What does the combustion chamber look like OP?
Modified by redtop91 at 4:54 PM 2/13/2008

[bruinbear714]

Looks like a piece of object was in the combustion chamber, or your valves are hitting the piston. Was the timing chain, cams, and crank set properly?

what the heck could have cause this?

[cunic]

heres the odd part of the whole situation...all four pistons look like that. i pulled my head cause my intake cam snapped

[KurbKiller]

Haha oh crap.My intake cam snapped too...Wtf.I wonder if thats what im gonna see when I pull my head.

[redtop91]

heres the odd part of the whole situation...all four pistons look like that. i pulled my head cause my intake cam snapped

I'm thinking effed timing. Checked it?....Lately?

[ELEMENT692121]

whats the head and the valves looklike???

[clss240]

the only damage i've seen from detonation are ring lands get blown apart theres a few pics of this in the "i blew up my ka-t" in the kat forum i've also seen holes burnt in pistons though i dont believe it was from detonation though just extreme heat? i've seen plugs melted all sorts of stuff mostly from nitrous/turbo

[ELEMENT692121]

detonation also causes poc marks or pitting in the surface of the piston and head ..you can usually see that the pieces will have spots that dont look smoothe anymore looklike a piece of unmachined cast metal ... caused by where the metal starts ot melt .. usually not shiny like in those pics you can see where the valves contacted the pistion and the other mark is prolly from a piece of valve or somthing .. why i wonderd what the head lookedlike.. the engine prolly jumped timing and banged the exhaust valves so hard it broke the cam ..

[My RB25]

whats the head and the valves looklike???

[cunic]

the valves r perfectly fine took the valvetran apart...there couldnt be a foreign object in my cylinders either because the cylinder walls arent scratched or scored...beats the heck outta me though what happend

[redtop91]

Bare metal hit bare metal somewhere. Has to be valve contact or something was in the cylinder. There's just no other possibilities. Possibly detonation but that is not a detonation mark.

[ELEMENT692121]

well ur cam being broke tells me that a valve hit a piston somwhere along the way .. it is not possible for a cam to break and engine to contiue to spin and not make contact somwhere ( if it is an interferance engine ) im new to the ka,s they are interferance right . i would assume so since mine compression tested at a touch under 200 psi .. im thinkin somehow the cam bein broken has to do with the valves hittin the piston ( jumped timing mabey ) .. but those are deff not det marks there was pyshical contact between that piston and another hard object .. were all ur plugs intact ?? ive seen plugs break and drop ceramic before ..

[redtop91]

they are interferance right

yep.

[ELEMENT692121]

i kinda figured they were since the compression was that high.. thanks for the insite..now i know

[youngun21a]

same thing happen to me,we install the cam and time them,and when we try to turn it it would stop half way,so the valve was makeing contact with the piston,then we check the cams and the chop had put them backwards,so we got them back from the chop,timed it again,turn it by the pully and turn freelie. my 2 cents

[b_rad]

check your intake valve guides in the port.