So after the drive to CA from NM, my engine has slowly developed this knock. When the motor was first started up, it had really loud valvetrain noise. Sounded like a sewing machine. But I read up on it and apparently that is common when running a big cam in an LS engine. So I thought nothing of it. Now when I arrived to CA, the car was running fantastic but the valvetrain noise seemed to be getting louder. And then the sound changed a bit from sewing machine to a steady knocking consistent with RPMs. I immediately thought "pushrods" because I am running a 7.325 length pushrod to accomodate for the LS7 lifters being taller, and my milled heads being shorter. So I grabbed a set of stock length rods off a guy on tech for free, installed them and nothing changed. I have triple checked all the rocker arms for damage and torqued them down to 22 ftlbs. I don't *think* that this is a rod knock and I am starting to lean towards collapsed lifters. Since I had so much bad luck with the TSP LS7 lifters from the getgo that is my next thing to try but ffffuuuuuuuu I dont wanna pull the heads!!! Have a listen and tell me what you think..... Oh BTW everything in the motor has about 1000 miles on it.

Oh and another question. In the last part of the video what I am doing is pulling the PCV valve out of the valve cover grommet, and there is a vacuum coming from the crankcase. As in the crankcase is sucking air IN instead of the vacuum line connected to the valve cover sucking air OUT of the crankcase. WTF IS THAT???? Anyone experience that before?? If I stick my finger in the grommet it will literally suck my finger into the valve cover, that's how strong of a vacuum this is. I'm baffled.

http://www.youtube.com/watch?v=8hmRGDSoEA4

 

Anyone?

 

Change the oil and cut the filter open

Shaving means you're pulling the heads and possibly replacing the cam

You may get lucky and it just be loose rockers, but it doesnt sound like it. Are you sure the pushrods are the correct length?

 

Sounds like valvetrain noise to me but I would still get change the oil and cut the filter open. Hook a timing light up to one of the plugs and see if the hoise is happening at valvetrain or crankshaft speed.

 

not that i am an expert but i had one do similiar to that and had to replace the lifters. also i have seen a valve spring start giving out and cause similiar noise as well.

 

Kill one cylinder one at a time & see if the knock changes. By change I mean from a "double knock" to a "single knock". If it does then you have a bad piston or wrist pin on that cylinder. If it does not change, just a drop because the engine rpm's go down, then it will be a cam or lifter. I would disconnect the injector to kill the cylinder. This will keep raw fuel out of the converters.

 

ok, so right now im experiencing the same kinda knock..i havent really done to much to figure it out...but you should be asking yourself...WHATS YOUR OIL PRESSURE???also i couldnt really tell but did the knock go away when your off idle??mine goes away and then comes back, only at idle tho...at start up my oil pressure cold is 40-45psi..then engine at operating temp is between 20-25psi...but my knock for sure isnt as pronounced as yours..good luck

 

some of the knock is the LS1s could be piston slap (if it's not been rebuilt). It sounds like a rod knocking, but then goes away after the motor warms up.

 

yeah, i just confirmed my knock..nothing really changed when i pulled the injectors at idle..no double knock..i reved the motor for 30 seconds at about 2000 and the noise was gone, but after about 30 seconds the nosie comes back...which i think could be a lifter pumping up...as for the motor itself, its a complete rebuilt stock motor, no oversized pistons or bearings..original pistons and cam, just new bearings, rings..original oil pump, just cleaned up and orginal lifters..any suggestions??

 

if it's original pistons, then you could be hearing piston slap

 

did you properly broke in the cam a soon as you got the the motor on your car after the rebuilt????

 

You don't have to break in a roller cam like you do a flat tappet.

 

if it is piston slap, i thought that only occured when the motor is cold, and once the motor heats up the pistons expand, thus eliminating the piston slap...i drove it last night last night probably around 10 miles and the noise didnt change and oil pressure hasnt changed either still around 27psi at idle...

 

some went away when the motor warmed up, I've heard mine at times after driving it for 30+ miles with a little noise in it.

 

so what did you do to get rid of it...also wondering if the knock sensors measure this and the computers cutting back on timing??