I have run up and down the boards for 3 hours now and can't find anyone with a problem similar to mine, so here it goes....

89 Formula 350, 117K on the clock, bought it with 115K. When I was changing the plugs, the motor had a plate on the side of it stating it was an AC/Delco remanufactured engine, .10 over on the rod and main bearings, .30 over on the bore. Unfortunately I can't find out when the motor was put in or by whom even after researching the VIN# through my Pontiac dealer. I figure that the motor has to be recently installed, 1-3 years, because it doesn't leak a bit of oil and is really strong. Car is bone stock, no mods at all.

I bought the car from a impound yard, so previous owner history is unknown. The car sat in the impound yard for about 6-9 months. The oil was dirty, drove it home, 40 miles (give or take) and changed the oil & filter, Valvoline 20/50 regular (not synthetic) oil.

2 weeks or so later on start up only, I started hearing what I perceived to be a rod knock coming from the #6 or #8 cylinder. This happens for approximately two seconds.

When Thomas (88aziroc) was up here in Phoenix looking for a GTA, he plugged in his computer dealiemobobbie and read what the computer was spitting out. He said everything he saw was normal, nothing out of the ordinary except that the TPS voltage was low, we adjusted it and the knock sensor wasn't working overtime.

Here is the stumper, at least for me. The knock only happens on cold starts or when the car sits for 10 minutes or more.

On cold starts, (temp gauge buried all the way to the left) the oil pressure (OEM dash gauge) pegs the needle to past 60 psi.

On warm starts (150 degrees +) I get a reading of 45 psi.

When running at operating temperature (200-210 degrees) at idle it reads a indicator or two above the red warning zone. Crusing speeds on the highway, it reads right above the halfway mark.

I just went outside and started the car (150 degrees on the temp gauge, been sitting for 2 hours) and the two second start up knock happened. Leaning over the engine, near the #6 #8 cylinders, I rev'd the engine yet I can't hear any knock.

I have an exhaust leak on the driver's side manifold so I know this is not the issue.

My roommate's friend who claims he has worked on cars since the first Camaro came out listened to the car and said rod knock right outta the gate. The guy is a little shady and I wouldn't trust my mother around him, so I'm really not taking 100% of what he says as true.

I was under the belief through the previous posts I searched that if my rod or main bearings were giving up the ghost, my oil pressure would suffer. My Haynes manual doesn't say jack squat about normal oil pressure and I "think" mine is ok.

Now thinking, could it be piston slap?

I'm kinda ruling out the cracked/broken flexplate scenario.

On top of this my damn diff cover is still leaking.

I'm just about ready to load my extra clips and start putting some .40 caliber hydroshocks into the car.

Someone help me help save the Bird before I kill it.

 

i use 5w - 30 Mobil 1 oil year round.. the difference in oil could be a problem. just a guess

 

I don't think that the viscosity on any oil would break down in less than a 2 week time span.

Who knows? I'm taking all reasonable suggestions.

 

I don't get all the posts w/ people threatening to do harm to their own cars if someone doesn't intervene and help. Go ahead, put a hammer thru the windshield a few times, pour gas on it and light up. Post pics.

It sounds like your oil pressure is below spec...figure it should have at least 10 psi of oil pressure for every 1,000 RPM the engine is turning. If you're cruising at 2500 RPM and have less than 25psi of oil pressure, that's bad. Especially running thick oil like you are.

Combine the knock with the low oil pressure, and it sounds like the engine is all used up. Great opportunity to drop in a crate motor!!

 

Kevin's rule of thumb for oil pressure is the old racers' WAG for what is considered adequate, not a spec for what a stock motor should actually produce. Don't take it as an indication of defects if yours doesn't meet that.

Sounds to me like there's nothing wrong with it, you just have the standard pressure pump, which will give about 20-25 psi idling and around 35-40 cruising. A cold motor will always have sky-high oil pressure. I wouldn't worry about it. The noise is even normal, that is usually a cam lobe or 2 where the lifter doesn't start turning right away, very common in flat tappet motors.

The pump that usually comes in these motors will give the same idle presure, but has a different pressure relief spring, to give around 50-55 psi cruising hot. You just don't have the HP pump, you have the generic one, so you didb't get the spring. No biggie. What you have is perfectly normal.

 

Yes, there are alot of people who want to take their frustrations out on their car but rarely if any ever do. It makes one wonder why are they so frustrated? GM's wonderful engineering? And with any 3rd gen owner it seems if it ain't one thing it's another.

I am seriously concerned about the noise in my motor, I can't get a straight answer from anyone in Arizona worth a ***t, no help from searching the boards and I wonder if I'm going to wipe a .10 over crank or toss a couple rods out the side of the block.

Yes, I can turn a wrench, I'm not ASE certified or anything, but I paint cars. Do you want to know how to color match, fix a fisheye while in the booth or handle tar on a body panel? Yes I can do that and I try to help out the other people who are not as knowledgeable in the painting end. I'm just asking for direction to go to find a solution to a problem that isn't normal.