the car is ttix with a forged bottom end ls6

automatic conversion. from 800 to 1900 I have a tapping noise that sounds like a rod knock. I have pulled the pan and cut open the oil filter and don't see any signs of bottom end damage. noise is more pronounced in gear and under load. I looked over the valve train and didn't see any bent pushrods, broken sprints or bad trunions.

maybe a bad guibo or lose flexplate ?? we put it up on a lift and it sounds deep in the engine. it's been this way for a couple of years now but I don't drive the car that much because the AC also needs a charge and has a slow leag

I'm thinking of doing a compression check next to see if it's a bad piston. can't really get to the bottom end too well with the bat wing pan.

the turbo system is due for an upgrade with bigger .82 exh housings and champion down pipes so it may be just easier to drop both front and rear cradles

I have a 4 post lift so I'm thinking of putting a sling under the body attached to reinforced stands to the rafters and lower the rolling chassis if needed.

car still make great power and drives smooth.

I hate to drop the cradles on this car without really knowing what the problem is.

thanks for any trouble shooting advice.

 

did you check the valve train really well.....or just kinda eyeball it? I had a similar type noise and it was valvetrain related. I was thinking engine rebuild/replace and was so worried....all for nought. Took it up to Fran at RPM and they sorted it all out. Good luck finding it and I hope it's an easy fix.

 

Did you check (physically) for pushrod play indicating a bad lifter?

 

Could it just be pinging? Do you have a way to check misfires or knock?

 

If you hang the body from the ceiling, please post a picture.

 

Have you determined where the noise is coming from? Could it be the cam bolts? All you have to do is remove the intake and valley cover to see if the sprocket is loose.

Here is a thread showing what I experienced when the cam bolts backed out: https://www.corvetteforum.com/forums...eo-inside.html

 

History ?

What has changed from when it last ran quiet, and now with the noise ?

 

Wrist pins on the pistons.

 

thanks for the suggestions. my first look at the valve train was pretty cursory. I'm going to pull it apart as it could be a bad trunion bearing and I just pulled the valve covers off.

could be a collapsed lifter, I'm going to try and pressurize the oil system and turn it over with a dial indicator and check the lift and see if there is any rockers rattling.

my mechanic buddy and I put it on the lift and he said "its either a rod bearing or a wrist pin"

wrist pin makes more sense to me.

time to tear into it. thanks for all the tips and thinks to look out for.

sure could be the cam sprocket bolts too or even the flex plate bolts that may have gotten loose.

thanks everyone!

 

You described mine to the tee. TTIX with auto swap. and same noise. Mine is a Lingefelter and I pointed the sound out to a few races and they said there is the same but worst..

 

same noise? any thoughts on if this is related to the auto swap

I did the swap 4 years ago and the noise started shortly after that, so I'm thinking it may be drivetrain rather than engine related.

my noise is pretty consistent in the 800-1800 RPM range and even a bit higher under light throttle with a load increase (thottle tip in)

If I'm giving it over 30% throttle, or above 2k, I don't hear it.

hoping it's not a wrist pin. time to call rodney.

my ZR-1 makes a similar noise and for sure it's the single mass flywheel.

this sound is similar only not nearly as loud. So I'm thinking the flexplate or coupler might have losened up.

that will take a torq tube pull to fix, so I'm hoping I can trace it before I tear into it!