Built engine is making knocking noise

[Spdrcr7882]

I had a engine built, and after a couiple hours of use the engine sounds like it has some serious knock. To make this easy it sounds like a nut is jumping around in the cylinder head or under the valve cover. However, when i took the valve cover off there was no problems what so ever. When the car is idling it makes this noise, but as soon as you start to drive it it stops completely. Does anyone have any idea what could be causing this problem.
Thanx
Justin

 

[1fast97gsx]

lifter tick?

 

[Spdrcr7882]

I have heard lifter tick before, this is much louder and more solid sounding.

 

[ADrewzki]

Maybe something transmission related? You said it's gone when you drive. I dunno. Weird.

 

[dsm1kenobe]

I had a engine built, and after a couiple hours of use the engine sounds like it has some serious knock. To make this easy it sounds like a nut is jumping around in the cylinder head or under the valve cover. However, when i took the valve cover off there was no problems what so ever. When the car is idling it makes this noise, but as soon as you start to drive it it stops completely. Does anyone have any idea what could be causing this problem.
Thanx
Justin

Do a search on "piston slap".

 

[Spdrcr7882]

I did a search on piston slap and it looks like piston slap stop once the engine warms up, but my knocking noise does not stop when the engine heats up. Any other suggestions?
Justin

 

[DsMWookie]

Was it factory parts rebuilt or Forged with all new internals?


possible broken wrist pin or Rod knock (if ur putting a load on the rod) it might cause the knock to go away. But if its intermitent like that I'd lean toward a wrist pin....seems weird happening right after a rebuild unless you resused the wrist pins.

 

[boostedinaz]

Have you double checked the timming belt? My buddies car did the same thing and it was all the valves smacking the pistons.

 

[Spdrcr7882]

The engine was built with all forged internals, and all new parts. If it was a spun bearing due to low oil problem it would make the noise all the time, right? especially under load
Justin

 

[DSMJim]

Your probablly hearing piston slap. IT's very common with forged internals. If the car drives fine, dones't over heat and it's blowing up then it's not a timing belt, or real knock or spun bearing issue.

Honestly piston slap with some pistons or if they are installed wrong is so annoying it sounds like a Diesel ideling.

 

[Spdrcr7882]

Ya, the car actually does drive perfectly fine, so i don't think it is the timing belt. THe only reason i was leaning away from piston slap, is b/c it makes this noise even when the enigne is warm
Justin

 

[boostedinaz]

What kind of pistons? Why not take it to your machinist and ask him if it sounds like piston slap? If he says yes then ask him how he is going to fix it. Not all forged pistons slap. If the machinist is good and worth his price should be able to assemble a short block that doesnt slap. JE has a bad design for out cars so if they are JE's it will most likely just do it all the time.

 

[TSIfreek]

It maybe the timimg tesioner arm hitting the tensioner rod. Mine does this and sounds like a lifter tap at Idle but goes away when the RPMs raise even with out load. Double check your timing belt tension it may be too loose and the tensioner rod is fully exteded. Mine does it every now and then and is sometimes gone at times. It has done this since day one. I would steer away from a bearing problem unless you hear it under load and you have good oil pressure. Piston slap will happen very litttle when cold but if its still making the same noise it not that. Also try the 3rd gen lifters seam to help with lifter tap if you are still on your stockers.

 

[DSMJim]

Ya, the car actually does drive perfectly fine, so i don't think it is the timing belt. THe only reason i was leaning away from piston slap, is b/c it makes this noise even when the enigne is warm
Justin

So does your muffler.

 

[blackGSX2g]

Double check the bolts on the cam gears and your other pulleys...those make horrible noises when they back out even a bit.

Also, I've got forged weisco pistons in my block and I've started it up around single digit temps here in MI winters without a hint of piston slap.