Alright I have a 2002 CHP B4C with 243,xxx I know with so many miles problems are to be expected but since the cost of a rebuild is close to the cost of a new LS1 which is less that $2k lower than the cost of an LS3 so I decided to replace my LS1 with the LS3 when the time comes however I don't have the resources to do any of the above at this time, so I'm trying to prolong the life of my LS the problem that worries me at this time is when I drive on the highway for the first 10 minutes on the highway everything sounds normal however after the first 10 mins or so a alight tapping can be heard its very faint due to the wind noice but soon after you notice it it gets louder and louder I searched online for an answer and found out that the fram oil filters can starve the engine of oil and cause the knocking so I changed my oil a few days ago with mobile one full synthetic (dexos1) snd a mobile 1 oil filter this time and it stopped for about 2 days now its back not as bad as before but is progressively getting worse, searching on the internet the only other thing that pops up is the common piston slap on cold start ups, so I'm trying here now

What could it possibly be? Changed oil stopped for 2 days seafoamed the engine and that made the engine run a lot smoother but engine still knocks on highway and only on the highway, I could drive through the city allday long with no problems but if on on the highway for more than 10 mins the knocking comes back please help! This car is my life I love it more than anything I own (or anyone I know) I know with this mileage I can't really save the engine so I just need to prolong it until I have the money for the new engine. My B4C is completly stock all it has is a K&N filter.
Any ideas?

 

Are you positive it's an engine noise? Does it still make the noise if you stop and let it idle?

 

try higher octane fuel? i know when i ran 87 mine would do that a little bit, car had a cam though...

 

Need more data

What is your oil pressure when riding down the highway?

 

When I get off the highway the knocking goes away with in a block or two, I'm positive it has to be the engine on the highway ill shift the car into neutral and the knocking slows down if I coast long enough it will go away when I shift back into drive the knocking returns with in a few mins . I only use high octane feul ($4.15/gal here) My oil pressure is at about 45 p.s.I.@ 75-80 mph around 2500 rpm. Over the weekend ice changed my spark plugs, cleaned my MAF and replaced my feul filter, my SES light isn't on either. After my tune up the engine is running pretty smooth but the knocking still returns

 

i would get one of those cheap stethoscopes and try to isolate whether or not it's a valve train or bottom end noise just after a hard drive.

Maybe you are having some oiling issue at higher RPM that would cause it to knock, what kind of oil filter do you run by the way?

 

Right now its mobile 1

 

my car did this exact same thing after my heads/cam install with ls7 lifters. Had the lifters replaced with comp oems and now it will very rarely do it if any at all. Lifter noise if pretty noticeable once you know it's that. Try searching on here and you can hear several clips of lifter tap.

 

My friends 04 gmc 5.3l did this exact thing. He let a mechanic look at it and he told for 3 oil changes to drive 1000 miles and change it. He did this and the problem went away entirely. The engine had 70k miles and it was definitely a lifter tapping.

 

exhaust leak perhaps? Start your car on a cold morning and while the pipes warm up get under and look for drops of water on the pipes...the hot gases escaping pinhole leaks will condense when they hit the colder air and you get water drops. Check it out!

 

Alright ill give the exaust check a try, and ill start the oil changes friday. Ill keep all of you posted