Knock on bottom end of motor. Spun bearing? Something else?

[theboz]

I just rebuilt this motor 460 miles ago. I have been breaking it in pretty easy. I have taken it up to redline but not everytime I drive it. It has run fine with no problems. Yesterday I noticed a knocking around 2500-3000 rpm's. Sounds like when I spun a bearing in my KA. Not quite as bad yet though. Is there anything that could cause a bottom end knock besides a spun bearing? I am probably going to pull the motor but want to be sure before I tear everything apart that it isnt something simple and stupid. This is my first SR (redtop) and first turbo motor (that isn't a diesel truck). Any help would be appreciated. I deploy for Iraq in 11 days and would like to have this done before I leave.

BoZ
Modified by theboz at 5:20 PM 11/6/2006

[theboz]

TTT

[Blown240sx]

If it is rpm dependent then it sounds like a bearing. Might want to just take the motor out and check the bearings. If it is a noticable knock at certian RPMs Id say your looking at Rod Bearings. If you just built the motor it could have been due to not using Lube for the bearings when assebly was taking place. Its very important to Lube everything excessivly since the motor will take a while to work in the oil.

[theboz]

I used a metric buttload of lube. This isn't the first motor I rebuilt, just the first SR. That is why I wanted to make sure there isn't some weird quirk with the SR motors that I might be overlooking. I figured it is probably a bearing. I should find out tomorrow.

[Blown240sx]

What type of pistons did you put in? I know some Honda motors with aftermarket H beem rods have a slight knock sound while running. Also is this knock only when the motor is cold? Cause aftermarket forged pistons can have piston slap when they are cold. Once they warm up it exspands and eliminates the movement of the piston.

[Hijacker]

did you prime the oil pump during assembly? sometimes if you don't the oil pump can take a bit longer to start pumping properly.

[theboz]

Blown240SX---The internals are all stock. I wish I could afford H-Beam rods and forged pistons.

tenkawa_akito---I did prime the pump during buildup of the motor. The motor has had great oil pressure the last 460 miles.

I am going to yank the motor and check the bearings. If one is bad then I hope the crank is salvageable with a good polish. Otherwise I will be posting for a new crank and rod. LOL I will keep you guys posted.

[Hijacker]

the only thing i could conceive that could cause a spun bearing then is dirt.