ruSSty

hey whats up guys i have a real big problem today i just got the car running and started after swapping my y-body motor into my 9c1.

i get no noise at idle but once the car holds a steady rev or gets reved at all it begins to make a real loud noise a cross between a clacking or thud noise....

i have done a search and come up with the possibiltity that it might be the FLEXPLATE CRACKED...

at idle with car fully warm temp 175 deg. you hear no noises and oil pressure is at 35-45 psi (new pump m155)
as soon as you rev past 1500-1800 rpms the sound is heard weather in gear griving or being reved up in park.
and yes the oil pressure rises with rev to as much as 80 psi i am kinda of crossing out the fact that maybe it is a rod knock cause i thought when you have to much clearences on the rod bearings pressure drops at idle and car makes screeching noises...

at idle the car is quiet.
if you get under the car on the drivers side you can hear it from below pretty good.
i am hoping that it is not a bottom end noise such as a FAULTY WRIST PIN..
i used a stethoscope to try to find and pinpoint noise but all i hear is chittering from r.r.'s and the exhaust but not one exact spot were the thud or clack is coming from.

now to eliminate valvetrain noise i am sure it has been reviewed on car
new lifters &
new pump
the car has headers so throw out the thought of it being a broken header bolt...

please guys i need some insight here before i junk this thing...

One more thing i would like to say also is that the car began to run really bad like sputtering on accel. after it started making noise. motor has approx 100k miles on it.
the car wouldnt perform down the block like it was being held back. i am thinking the reason for that is cause the PCM is picking up knock from whatever is making the noise and super retarding timing to prevent engine failure..

does anyone know what it could be:

piston wrist pin or cracked flexplate.

http://www.geocities.com/sinbinder/REC_0002.WAV

my noise sounds something sort of like this..but in the wav file i think this car is at idle when it was recorded.
My noise is similar, but it does not make any at idle only holding rev or while reving.
like said great pressure all round.

that same clack....

crAzy95z28

my opinion could be the roller rockers are loose!

take off the vavle cover and check them out!

ruSSty

let me also add that i have also adjusted valve lash bout 2-3 times already..sorry.

clai9

Sounds like a loose rocker or a header leak.

ruSSty

aw man this isnt going to be easy

stroked383z28

I had a cracked flexplate on my old 95Z once. You could definately hear it at idle. Then again it might depend on how bad it is cracked as mine was cracked almost all the way around. It's worth getting under there and taking a look at it.

ruSSty

i checked out the flexplate and that wasnt it. so i decided to drop the oil pan and guess what i have a SPUN BEARING oh well time to repair..it was the last piston to the rear of the block, unbelivable 100k mile Y-body motor had no problems then from day to day i SPUN 1 aw man this suck...
i am willing to do a patch up job to get by until i can put some funds aside to build a real bulletproof b/e.

i was thinking of throwing a .10 + in and cleaning up the crank to see if this will get me by.it worked once for me on a little 3.8 buick n/a i owned and never made a noise again after i replaced it.

does anyone have some helpful info on how to go about patching up this SPUN BEARING issue any insight at all would be greatly appreciated.