New LS1 Owners - Newbie Tech - HELP! After LS6 swap a P0102 code and Knocking / slapping / loud noise

Good Evening (I Wish),

I was feeling good after my LS1 to LS6 swap and fired her up and immediately heard a loud knocking / slapping noise from the engine. It is regular with the idle, which seems very fast as well. The only code is a P0102 code for the Mass air flow sensor.

Following some advice on here I disconnected the sensor and it still is making the slapping / knocking noise. I have no idea what to do next. Please help!

I also put on a BBK 80 MM throttle body and the throttle cable is loose, like it seems too long. This is a much lesser problem than the noise.

Oh I forgot to mention that I started the car before I had everything tightened down. Do not do this ! Immediately it went to full throttle for 10 seconds or so, and I'm not sure if that had anything to do with the noise.

Oh, I also broke the oil sending unit sensor at the back, but I replaced that with a new sensor.

Anyone have experience with this?

Oh I forgot to mention that I started the car before I had everything tightened down. Do not do this ! Immediately it went to full throttle for 10 seconds or so, and I'm not sure if that had anything to do with the noise.


That wasn't smart, you already know that.

You could have collapsed a lifter or bent a pushrod, maybe something else.

You might want to pull the valve covers and check your top end for any loose parts.

Got a vid of it? That might help a bit.

Oh I forgot to mention that I started the car before I had everything tightened down. Do not do this ! Immediately it went to full throttle for 10 seconds or so, and I'm not sure if that had anything to do with the noise.

^^^ WHY? why would you do such a thing? Curiosity killed the cat... You know that right?

sounds like you blowed her up

^^^ blowed her up? Ya he did that. Possibly. Just crazy he would start up with 1/2 a engine lol... Come on now...

this has to be a troll thread

^^^ whata u mean? I would like to help out but I'm not even sure where to start from...

There's no way anyone who can build an engine/install an engine would

"Oh I forgot to mention that I started the car before I had everything tightened down. Do not do this ! Immediately it went to full throttle for 10 seconds or so, and I'm not sure if that had anything to do with the noise."

especially before priming the oil pump if the motor had sat for a very long time.

Not a troll, just a dumbass. I had the Manifold and everything plugged in and the bolts in but not tight. I thought "lets see if everything is plugged in correctly" not thinking it would blow up.

I now know that a vacuum leak, or 8 of them is a very bad thing. I am calling some shops in the area for a diagnosis. A very hard lesson to learn.

Any chance you have a loose converrter bolt?

not sure if on ls6 but check your AIR tubes, lifters, and rockers

Well it is going into a local speed shop on Tuesday to see what is ticking. The guy there said it is probably lifters and maybe a rocker. We'll see. I'll post back when I get the diagnosis.

Well, the bad news is bad. My dumbassery has bent 7 push rods, and they don't think that is the extent of the damage. Unfortunately they ran it after the pushrods were installed and it is still making noise. Bad News.

The shop that I took it to said that they would recommend purchasing a new GM long block and having them install it. I was told that putting in a real GM long block would be preferable for resale etc. because it looks stock.

Supposedly the long block would be $3,400. Labor and extra parts are estimated at $2,100. $5,500 is the estimate. Does this sound right?

I'm going to call around tomorrow to get a second quote but I was wondering if you guys had any recommendations on long blocks etc.

I looked up the KBB value of my 2000 Trans Am and they said it was still between $9,500 and $12,000. I couldn't believe it was still worth that much.

Take it to a performance shop and have it rebuilt. It cost my step dad around 3.5. I wouldnt buy new block.

Yes I can believe ur WS6 is worth that. My 2000 SS is worth about the same. Miles really really count. Options and age count. But not as much... Best of luck.

Well if the pushrods were bent.You might have done some damage to the lifters.I don't think you need a new long block.But i don't know without looking at it.I would try fixing it before i bought a new long block.Forget KBB prices.this economy sucks.

Well, the bad news is bad. My dumbassery has bent 7 push rods, and they don't think that is the extent of the damage. Unfortunately they ran it after the pushrods were installed and it is still making noise. Bad News.

The shop that I took it to said that they would recommend purchasing a new GM long block and having them install it. I was told that putting in a real GM long block would be preferable for resale etc. because it looks stock.

Supposedly the long block would be $3,400. Labor and extra parts are estimated at $2,100. $5,500 is the estimate. Does this sound right?

I'm going to call around tomorrow to get a second quote but I was wondering if you guys had any recommendations on long blocks etc.

You need to find a different shop, of course they are going to sell you a whole brand new motor. I'm not even going to comment on the other crap they tried to tell you.

Find someone with LSX experience.

Take it to a performance shop and have it rebuilt. I cost my step around 3.5. I wouldnt buy new block.

I agree no need to buy a new long block, take the heads off and check for damage first if they are ok get a shortblock if you cant just rebuild the valvetrain, you can get one from a sponsor like Thompson that is a stock rebuild for next to nothing.

:corn: lol