ENGINE RATTLE

[arcticmopar]

Hey guys, My 383 all of a sudden started with a loud clunk/rattle noise last year. I was just warming it up on hi-idle and when I kicked it down it sounds like a large rock or two in a dryer? It has a tinny sound to it like something hitting the oil pan or valley pan. I have since dropped the oil pan, all rods and mains were tight and not discolored. I removed the flywheel cover(auto) and found everything tight and  no marks of something hitting.(same for the oil pan and windage tray) I removed the fuel pump and checked the pushrod,no marks or damage. I pulled the intake,checked all pushrods,rocker arms and reset the lash(hyd lifters). The only things I found was a slightly loose oil pickup and the fuel pump was a little loose too. The noise is still there. It always has and still does go away a few hundred RPM off idle. I have even hit the Hwy for about 50 miles at 3000 RPM and shifted at about 4500-5000RPM with no problems but if I hit a traffic light it makes so damn much noise idling people two blocks away turn and cringe,plus you can feel it all through the car. I have no clue what to do next other than have another engine built!

[Strawdawg]

sounds like a cracked flexplate. 

Does it make the noise with the converter unbolted and pushed back?

[72cudamaan]

sounds like a cracked flexplate. 

Does it make the noise with the converter unbolted and pushed back?

Yep, have to agree.

[arcticmopar]

Hmm never thought of trying that, I checked for loose bolts there but didnt remove it. Can you run an engine without a torque converter or a std trans flywheel?
Looks like I got something to try this weekend.    Thanks.

[Strawdawg]

yes. unbolt it, push it back....

Normally, the cracks are very hard to see as they are hair lines and go between the bolts to the crank....takes a good mirror and a brite lite, often

[arcticmopar]

THanks Strawdawg will try that tomorrow...have the Girlfriend comming by to entertain tonight.

[Strawdawg]

Let her change the oil......

[b-bak73]

I would also check that the harmonic ballancer isnt loose on the crank,i had a 400 chevy years ago that made a similar noise at start up and idle,it had a slight engine vibration which eventually rattled the ballancer loose on the crank.

[arcticmopar]

Well I think I found the problem...mix-matched parts. I have a 5/16 thread torque convertor with a 7/16 size flexplate. three of the four were loose, gues I forgot locktight too. I know I loctited the bolts to the crank beforeI dropped the motor in. Now for my sketchy plan I will use loctite but also see if the machine shop can cut down some 5/16 washers to make a shim. I know the correct fix is to drop the tranny and get parts that match between the money and the time to ship something in...I just want to drive LOL. Any thoughts?

[Strawdawg]

Pull the converter and have the machine shop drill/tap it for the larger bolt?

Make sure the flexplate holes are not wallowed out

pain in the neck, but better than a new engine