What did I screw up?

[hsi111]

I have a 1997 Tahoe that I bought a few months back with a blown head gasket. While diagnosing my problem, I had the bright idea of sticking a screw driver in the spark plug hole of one of the cylinders to find TDC. The bad part is I used the starter to bump engine and my screw driver came out all mangled. Live and learn I guess. Anyway, Now I have a knock that I didn't have before. This is what I know.... Head had bent valve on that cylinder so I got another head to have checked and rebuilt along with other one. I installed new roller lifters trying to fix problem...no help. Piston looks ok. Compression is ok. Noise sounds kinna like top end but really hard to tell. Noise will quieten for about 15 seconds then come back if I tighten down on that valve. All I can figure now is that I wiped a cam lobe when I did that but I am wondering if their is a chance that that could have messed up rod bearing. What do you think? All input is appreciated.

 

[SunlitComet]

Screwed up lifter maybe. But how did you do your valve adjustments. If you ran engine on it would knock only when spark wire is attached but not knock when wire is removed that would be rod knock.

 

[hsi111]

I forgot to post that I put new lifters in it when I was trying to fix it (They are roller lifters). Noise does not change when I pull plug wire. As far as adjusting lifters, I did it by the book while it was apart, then had to adjust them running when I cranked it cause they were still noisy. With it running, I loosened them till they clattered that tightened them 1/2 turn. 3/4s turn boggs motor.

 

[SunlitComet]

How about a bent rod?

 

[hsi111]

Checked those...all good

 

[Donnie Yukonie]

ouch is there any missing pieces on the screwdriver? in aviation we call this FOD and it can cause headaches

 

[bowtiefreak]

I would have guessed bent rod.

 

[hsi111]

No missing pieces of screw driver. Remember I have had heads off. All ok except a very small nick in piston. I am a little surprised that nobody is thinking cam lobe here.

 

[SunlitComet]

Honestly that is hard to fathom right now just because of a screwdriver in cylinder.

 

[Trippers99hoe]

Broken piston skirt,that is my bet.