Loud knock after oil change?

[bvance554]

Did the 4.3's by any chance have the piston skirt slap issue that the V8's did? They say its the same engine design as a V8 with two pistons removed, so it probably uses the same pistons. Some audio would be helpful. If its piston slap just drive on with the recommended grade of oil.

 

[lancelot50]

Why the 20w50 plus lucas? Well i live 25 miles away and when he bought truck i went up to check it out and like i said it ran good no noise.the stupid oil combo was his granpas idea! He didnt ask me first or i would have red flagged that!even when i put the recommended oil back in and gave a no expert answer to why as in its too thick for the passages and this aint the 50's.he replied thats a bunch of @#@# b.s. engines are same as then.and then i wondered if it could have been the issue.so id like to give it one more shot by takin the flimsy china made tming tensioner out and putting a stock chain in eliminating the balance shaft gear.maybe not too much damage plus the oil and filter you fellas recommended

 

[Bgallagher]

Originally Posted By: NormanBuntz
So you're using an STP oil filter? Lose that thing, install the correct ACDelco and hope you got lucky.


+1 stick with the OEM filters on those engines. They can also run on just about any oil so I wouldn't feel that would make a huge difference.

 

[aquariuscsm]

A name brand 20W50 wouldn't hurt a thing. It's the Lucas added to it that threw it all out of whack.

 

[Robenstein]

Originally Posted By: aquariuscsm
A name brand 20W50 wouldn't hurt a thing. It's the Lucas added to it that threw it all out of whack.


Yep, Lucas is about like straight 70 oil if I recall correctly.

My mom has a GMC with a 4.3 and it is a bit tired. Instead of 5w30 I just started using Mobil 1 0w40 in it. Has good oil pressure and it stopped using any measurable amount oil. Not bad for a nearly 20 year old mill.

 

[lancelot50]

Again the oil lucas combo was my sons granpas idea.and the 20w50 was about as opposite of name brand as can be (family dollar)aka 2 bucks qt.i guess im terrible at getting an idea across?when i first heard the knock its sounded like piston!then read about balance shaft!i jumped the gun too soon,didnt diagnose!none of it made sense after oil change except the oil/lucas/filter combo.so my question is instead of ditching engine.i want to take out timing tensioner kit,install good stock one!eliminate balance shaft gear!ac delco filter! Maybe some lifter fortifier/seafoam? Do you think its worth a shot?

 

[methusaleh]

Let's stop right there. Any chance there is a bottle left? Or that someone could return to the store and look at the label? The oil may have been so far out of spec as to offer almost no protection (ie something like SA or SB).

 

[lancelot50]

Well fellas i had my sons truck towed down to my house.he told me a couple days prior that the knock got much louder real fast!!.so long story short the original noise was a bad spot on roller cam 4 cylinder.the lifter was catching flat spots and knocking.well the damage from dollar genral oil/lucas was done!so i went on and pulled engine annd 4 rod journal spun,took rod and crank as well.amazingly the rest of engine looked great!so am in process of repairing now.crank,rod,gaskets good cleaning etc.