Hey Guys,
I have been having a scratching/scraping sound coming from my motor. Here are the symptoms:

-1991 305 TBI/auto with 125,000 miles.
-It sounds like metal-to-metal scratching
-It only happens at idle when the trans is in park
-Its not constant. It will turn on & off quickly & randomly.
-Its coming from the harmonic balancer area. (I used a piece of vacum hose to track it down)
-I removed the belt to see if it was another pulley... But even with the belt off, it didnt go away.
-I want to say that its the timing chain. I sounds like the chain is loose and is floping around scraping against the timing chain cover.
-The car seems to run fine even with the problem.


I am about to tear the timing chain cover off, to see if I am right. But I want to see if anyone has any other ideas before I get my tools out. Are there any checks I can perform to see what the problem is? Are there any bearings in that area that may go bad and cause this? If so, can they be replaced without pulling apart the block?

 

It's probably your timing chain. They do stretch quite a bit and yours is rubbing on the timing cover.Let us know what you find when you open it up.

 

Probably not the timing chain; those usually either are loose or they're not, they don't change.

Could be the inertia ring of the damper rubbing on the TC.

Could be the cam bolts scraping on the inside of the TC. Sometimes they back out - very bad. Usually the oil pump and the lifters will create enough rearward force to hold the cam all the way back away from the TC.

If it's not the inertia ring, it's inside the TC, whatever it is; in that case, you'll have to open it up.

 

I dont think the timing chain is changing... I am thinking that its floping back & fourth. I am unwilling to pull this motor apart, its just not worth it. I really hope its the chain... Cause if its not... I will probalby just drive it till the motor stops and then park the car till I can get a new motor for it.

 

I'm with RB. I don't think the chain is rubbing on the cover unless the cover was dented in or something. Have you ever taken the timing chain, set it on a table, assembled. Pinned the 2 gears in place then try to lift the chain on one of the 'sides'? Not an easy task.

 

Well I took it all apart tonight. I think the problem was my timing chain. I am not sure how much I am susposed to be able to move the chain back-and-fourth, but I am sure it moves too much. I am able to move the chain back and fourth about 3/4"!!!! I doubt that it is susposed to move this much. I am going to post pics tomorrow morning. Also, since I have all of this stuff apart, what kinda things can I do to get a few extra HP. I was thinking about replacing the waterpump with an aftermarket unit. That thing weighs A FREAKING TON!!! Any suggestions on what pump to get. Or is there anything else I can do to get a few extra HP?

 

Here are the pics from last night...





Can you see a difference? hahah

 

There's nothing really wrong with that. Pretty normal actually.

You hear alot about timing chain "stretch"; they don't do that. It's a myth. They do wear in their bushings, but that one is fine. Stock sets have a chinesium gear with little chinesium gums and phenolic teeth, and the phenolic turns to dust and chips off, exposing the gums, and allows the chain to flop around everywhere as the whole thing is just about getting ready to fail utterly and render the engine inoperative. That one is a replacement gear, that's made out of real metal. That chain isn't even very old. Personally I wouldn't bother with replacing it, it won't make any appreciable difference to how the engine runs, and will probably be back just like that within 10,000 miles or so.

What I'd really like to see a pic of, is the inside of the timing cover, at the bottom, around the crank gear (like lay the cover on the ground and take a pic from what would be the top inside, at a 45° angle); and a pic of the front of the TC around the balancer area.

If anything is rubbing, it will leave traces. I don't really see anything wrong in that pic, except that it looks like the oil hasn't been getting changed enough at some point in the engine's life. But that's nothing that a quart of ATF in the oil for a few thousand miles wouldn't fix.

 

ITS FIXED!!! I got everything together last night and started her up!!! NO SCRATCHING SOUND!!! The engine is quieter in general too. Im so glad that was the problem. I just hope that I dont have any problems with oil leaks now. The car runs good too! While everything was apart, I removed the A.I.R. pump, bumped up the fuel pressure, ported my Throttle body, and bumped up the timing. Car runs really strong now. Im very Happy