What is causeing this knock? Video included inside.

[Wingnut87]

http://www.badassperformance.com/misc-vid/knock.wmv
(2.8megs)

First:

I realize there are a lot of threads about knocking problems and I have searched and read them all (I think). Everyone describes the sounds differently and I’m not sure if the problems are the same as mine. Because of this, I uploaded a video of the engine with the sound. Hopefully, someone who has solved this problem before will have an extra minute for me!

History:

The car is a 1987 Rx7 with a 2000 Camaro SS w/T56 engine transplant. It has been running poorly for about a year until I found out I plumbed the fuel incorrectly and was getting too much fuel. I installed a corvette fuel filter/regulator and the car ran great for three days. Then after filling up the fuel tank and getting hard on the throttle, the knock showed up.

Problem:

Engine knock sounds like a higher pitched Diesel sound. It is RPM dependant and louder at certain spots. I can’t tell if it is every, or every other RPM that it knocks.

Things I have done, or know about:

Oil pressure is 40psi when cold, goes down to 30 when hot and gets to 60 with higher RPM. I have EFIlive scan tool at my disposal. I have not noticed anything out of the ordinary. No knocking detected, LT fuel trims around -5 to -8%. I think my fuel pressure is a few psi low at 54. I am new to the software and willing to run more logs if it could help. I ran the balance test and all cylinders seem the same, but each time I run it, some cylinders are left out. They are different each time. I don’t know if this is normal. I’m still trying to fix the VSS sensor. Spark plugs and wires are new. I also put in a bottle of NOS octane booster when someone suggested bad gas (I got the gas at a newer and popular BP station). People suggested the engine was hitting something. I don’t think the engine shakes at a high enough frequency to make that noise. There are some close fits, but I haven’t found anything hitting. With a homemade stethoscope, I think the noise is most evident when I touch and front of the oil pan or the water pump. The knock is still there with the main belt removed. The car feels fine power-wise, but I’m afraid to really drive it much. I don’t want to do more damage.

My only theories:

Get the fuel pressure up to 58psi with a booster pump.
Bad main or cam bearing?
Bad timing chain?

The engine has 40-50k miles on it. It ran great for three days. What could cause this?
Please help, thanks!

Tom

[joecar]

Tom,

Could hear it under no load reving, so I would say that eliminates ignition ping, would you agree (does log show any KR...?)...?

Does not sound like piston slap at all, but does sound mechanical.

I'll have to replay the vid a few more times...

Joe

[johnv]

Ouch doesn't sound good . could be a bent pushrod ? not to hard to check.

but sounds like its comeing from deeper inside engine maybe big end brg or piston.

[Wingnut87]

There is no knock retard in the log. I just can't believe this engine would need a rebuild at 40k miles. Maybe I just got ripped off. Is there anything I should check before I pull the motor and start tearing it down? Is there anything I could have done to cause this? I don't want to get the motor rebuilt and then blow it again.

[joecar]

Get some oil from the engine drain plug into a bottle and see if there's any metal.

[Highlander]

the engine is not knocking... if i where to guess.... i would start easy does it... the last sound i heard like that... it was piston 5 and 7 broken....

Well.. reality is it could be anything.. I would suggest.... check for pushrods or loose rocker arms... rocker arms loose will sound similar also (can't judge perfectly from video).

I have not seen these engines with a bad cam bearing... on the Vin M 3.1L i have many times but not LS1.

After you do that i would suggest a HEAVY engine FLUSH first. I have found that lifters sound (but yours is a bit heavily) when lack of maintenance.... if that doesn't cure it, you will have to dig deeper... These engines DO NOT need a rebuild at 50k.

[Highlander]

Does the check engine blink?

[dissonance]

try to pin point the sound better with your stethoscope... but it does sound like a rocker or rod to me...

also get under the motor with the stethoscope and "see" what you can hear

[Wingnut87]

After the knock started I changed the oil. There was a pea sized wad of metal dust on the magnetic drain plug. The sound is loudest in the stethoscope on the oil pan closer to the front. I hear it a little on the water pump (even when belt removed).

[Chuck L.]

After the knock started I changed the oil. There was a pea sized wad of metal dust on the magnetic drain plug. The sound is loudest in the stethoscope on the oil pan closer to the front. I hear it a little on the water pump (even when belt removed).

The knock is too "deep" sounding to be a rocker. It sounds like a brg to me.
The fact it's a "used" engine, would make me think it's had it's "tongue hangin out", one time too many, and the lower end is toast.
If it were mine, I'd be pulling it, and taking a look, before I joined the DOTCC.. "Drive over the crank club"..:sad:

Might try to short out the plugs, one at a time, and see if the sound changes...That would indicate a rod brg going south.