Knocking sound VX L67

[funkyman]

After I did an oil change using a cheaper oil, car developed a bit of a timing chain type rattle sound when under load (like accelerating up hills) I wrongly assumed it was a stuffed cat converter after the coil failed twice.

Long story short, I gave it a bit going up a huge hill then there was a thud and it conked out. Now it has a persistent knock.

Already ruled out balance cam, timing chain and supercharger.

Any educated guesses of what it could be?

 

[_R_J_K_]

What grade of oil was it?

 

[funkyman]

What grade of oil was it?

15W40

 

[gohrdrgomad]

After I did an oil change using a cheaper oil, car developed a bit of a timing chain type rattle sound when under load (like accelerating up hills) I wrongly assumed it was a stuffed cat converter after the coil failed twice.

Long story short, I gave it a bit going up a huge hill then there was a thud and it conked out. Now it has a persistent knock.

Already ruled out balance cam, timing chain and supercharger.

Any educated guesses of what it could be?

It could be valve train issues, it doesnt sound to be running sweat Y/N?

 

[lowandslow]

My bet is Big or little end bearing. The knock is too "heavy" to be valve train for mine.

 

[vr304]

Wouldn’t hurt to pull the rocker covers off and check the rockers themselves, check for any broken valve springs, pull the pushrods out and see if any are bent, maybe a stuffed lifter also

 

[funkyman]

Thanks. Will do that.

Wouldn’t hurt to pull the rocker covers off and check the rockers themselves, check for any broken valve springs, pull the pushrods out and see if any are bent, maybe a stuffed lifter also

 

[funkyman]

It could be valve train issues, it doesnt sound to be running sweat Y/N?

I'm too scared to drive it currently, but sounds bad, hoping I don't have to pull the whole engine out. Going to do what vr304 said when I get a chance.

 

[funkyman]

Part of the piston is broken off, it may have been caused by detonation due to previous coil failure(s)?
Apart from the obvious I was surprised by how little damage there was, the piece of piston was nowhere to be found.

I will take bottom end out soon, I expect big end bearing is gone, hopefully no other nasty surprises.

Questions, even tho its too soon to ask:

What are my chances of getting a second hand or single replacement piston? (I know an Ecotec one is not the same)

Am happy to get the crank machined and buy necessary replacement parts and reassemble it myself, but is it even worth doing this repair anymore?

 

[delcowizzid]

Find a piston and rod from the same year l67 and go again probably 2 valves as well .sometimes the bits of piston go into other intake ports not just out the exhaust .would of detonated slightly and that's it game over the pistons are real thin on top