99blancoSS

iTrader: (115)

does it sound like its with every other rpm of the engine?

JPH

iTrader: (2)

We don't have any exhaust leaks correct?

Intercooler2

iTrader: (24)

At idle nothing. Just like a stocker. Cruising up to 3500 nothing. Blipping to 5000 with no load nothing audible. Take it out on the street and crack on it over 4k and it makes the noise until you let off.

Intercooler2

iTrader: (24)

No. It doesn't make any noises. I should take a video... may have to if we can't find what it is.

Intercooler2

iTrader: (24)

I hate to tear the motor apart, find maybe nothing then put it back together and still have the noise. What would the majority here do?

I don't have any codes either. I thought... misfire related but it doesn't and no codes.


Oil pressure is fine so that means can't be a rod bearing. I'm in fear of holing my block or sending something through a piston taking the whole motor out. Things like this are next to impossible to find!

We are going to do a compression check but doubt we will find anything.

99blancoSS

iTrader: (115)

When you checked for lose rockers did you rotate the engine by hand to get it on the base circle for each cylinder?

Just re-read post 1... are you sure your not getting actual engine knock as in pre-detonation?

After-market cats?

69LT1Bird

iTrader: (1)

What kind of flexplate do you have? I see you have a good converter, perhaps a cracked flexplate.

Intercooler2

iTrader: (24)

I don't think. It was dynotuned and the other day I added race gas just to see. I would need a scanner to see knock though right?

Only one side?

Intercooler2

iTrader: (24)

It's a CAT SFI rated plate but no saying it couldn't be. Can't see unless I pull the trans though right?

Intercooler2

iTrader: (24)

Just wanted to add for those offering up ideas... it is load related!!

Only when you thrash on it

5.3LJimmy

iTrader: (10)

Have you pulled the spark plugs to see what they look like? If you have a head gasket dripping water externally, then it's possible that you are also getting water intrusion into the cylinder. You should be able to identify this by looking at the plugs to see if one or more appear to be steam cleaned. My guess is you are getting water in at least one cylinder and the sound you hear is detonation. No amount of race gas will make water burn! That leaking head gasket needs to be fixed anyway, so pull the head and inspect the lifters while you are in there.

Intercooler2

iTrader: (24)

Would a compression test show this? No smell out the exhaust. No mist of water vapor.

Intercooler2

iTrader: (24)

Spark plugs look normal.

Intercooler2

iTrader: (24)

I also thought the cylinder pressure would be greater than any water pressure and should keep it out unless their is a crack. Still sounds worth looking at some if the compression test shows anything. I don't know if what you laid out would apply here since I don't get it 0-5000 hitting on the throttle at idle or when we had it in the air running it up through the gears hard and not getting it.

JPH

iTrader: (2)

Listen very close to the intake and valve cover are around #1 and see if the noise is ther?

Intercooler2

iTrader: (24)

Area between those two? Am I listening for exhaust, mechanical?

Brakemotive

iTrader: (73)

Based on what you've described it sounds like detonation. Quit beating on it till you get a data log on it to rule that possibility out.

Edit: How did you prep the block surface and gaskets? Did you use any copper spray etc? If I had water weeping from my heads they would be off ASAP.

Intercooler2

iTrader: (24)

New heads cleaned, block scraped and cleaned, all holes dried. Two light coats of copper spray both sides of the gaskets.

Intercooler2

iTrader: (24)

So we were planning on doing a cylinder by cylinder leakdown test tomorrow A.M. Will that show any head gasket issue or detonation associated with it? I would rather not drive it over to get a log since it is 40 miles.

Brakemotive

iTrader: (73)

It's common practice on here, but if the block is prepped properly you don't need any copper spray. I've talked to cometic about it and they specifically advised not to spray anything on them. I followed their advice and haven't had any sealing issues FWIW.

A leakdown test will tell you if your losing compression in a cylinder. You may be able to hear where the air is escaping to narrow it down. It won't tell you anything about detonation. What's your compression look like? Also, what thickness is the gasket? What size heads? Just trying to get an idea of your quench...