Beetha

Hey guys i need help trying to figure out what is the cause of this terrible loud thud/knocking sound coming from my engine , the noise comes immediatly when i go to start the car . I havent even tried to shift out of park since this happend because i dont want to make it any worse if its not bad already . 96` LT1 Caprice Classic 9c1

davidc212k

iTrader: (3)

it could be a exhaust headers leak. time to replace gaskets. i had this issue about 2 weeks ago and i went ahead and purchased some seal4good gaskets for a longer fix.

93 LT1 Vette

Anyway to post a video or audio clip? It would make troubleshooting a hellva lot easier.

shbox

No way to tell what it is without some sound.

cardo0

Use a stethoscope (<$10) to locate source area - crankcase or vlv train. Leaky headers will sound more like a lifter tick than a knock.

Does the noise continue after warm up? Can u rev it a little and hear it increase with rpm? If its a rod knocking putting it in gear ain't make much diff - damage is done. Put it in gear and listen for change under load.

Did you make any changes lately? After a cam change i had loud knock on startup - found it was the crank flange (2 piece seal block) hitting the flywheel inspection cover (small bent lip). Worried the heck out'a me.

Hope this helps,
cardo

Beetha

i haven changed anything latley just been doing regular maitnance . this noise sounds more like shoes in a drier but more consistent . I will be posting a video later on today so i can give u guys a better picture . You`re right noway to really tell without an audio clip . And i dont even want to leave it running long enough to let it warm up thats how bad it is . Thank you and i will be posting the vid in a few hours

Rockosocko

How long have you owned it?
Was it a police auction car, or was it ordered that way? If it was an auction it might have all sorts of things loose or worn like engine and trans mounts.

pull your torque converter inspection cover and look to see if the flexplate is cracked or bolts loose..
Then while your under there, take the T/C bolts off and push the converter back a bit and restart the car. Does it still make the noise (if it goes away, it might be the tranny)

Just a few thoughts.
E

Beetha

Hey guys im sorry I couldn't post the video, my phone just wont let me. But im assuming that im just going to have to have the engine rebuilt going off how it sounds. The guy I had bought the car from had told me the engine and tranny was once rebuilt at George Gates Automotive at 99,957 miles on it and i bought it at 176,000 miles on the dash it and right now it has 179,000miles on it so I dont know why the engine already has to be rebuilt . My question is much would it cost for a stock rebuild for the lt1 ? Im also looking to re-use whatever parts I can that are not in need of being replaced...