2003 Gt With Rod Knock

[rockyracoon]

Hey gents,
I have what seems to be a rod knock so my question is in regards to the teardown for inspection.

So in order to inspect the bearings and crank journals I assume I have to remove the timing chains
and bearing caps. am I missing anything ? would I be best to buy a crank kit ? will the kit come with standard rod and main bearings ?

 

[rockyracoon]

wow no one has pulled the crank out of their 4.6 huh .

guess ill just have to do like I allways do and figure it out for myself.

 

[bhuff30]

First, I would question if it is really a rod knock. The timing chains in these engines can make quite a bit of noise too. So how and when does it make noise?

Assuming is is rod knock: Is the bottom end stock? Do you need to upgrade to something stronger? (ie, are you making or plan to make more than 400rwhp?) If not, then you should seriously consider a used engine or used short block. It would be a whole lot easier (and cheaper!) than pulling apart and repairing your current engine. Most likely, the crank will need to be turned or replaced and you are adding up dollars fast in that case. To do the job RIGHT, you basically need to rebuild the entire engine because the rod bearing sent metal everywhere.

If you need a stronger bottom end, there are plenty of companies that offer built bottom ends, like MMR. Sure, maybe you can save a few bucks building the bottom end on your own, but why not let someone else assume that risk?

Last note, PI heads on an NPI bottom end can make a potent combination due to the bump in compression. Just something to consider when replacing your bottom end.

 

[rockyracoon]

wel it was making the knocking noise that woud get louder with increased RPMs pretty much all the time, including idle except when in a higher gear while going slower (in 4th gear going 20 MPH) which I guess you would say when lugging the engine.

As far as my power goals im probably going to stay close to stock.

I purchased a used (miced and polished) stock crank, with bearings off of e-bay for 80 bux shipped so assuming it (the noise) was a bearing knock I was going to pull the motor and go that route.

Would rather not go NPI block with PI heads as I want to be able to burn 87 octane.

 

[bhuff30]

I suppose it could be rod knock, but the bearing must be basically completely gone now.

Rod knock is usually loudest around 2-3k rpm, at light load. At idle, high rpms, and heavy loads, it often goes away completely, until it is really bad. If it is rod knock, then it has pasted that phase and is SEVERE.

I would do some more diagnosis before tearing things apart. Use a tool (like a stethoscope) to better locate the area of the noise to see if it really is from the bottom end. I wouldn't be surprised at all if it was a valvetrain issue, since the noise is constantly there under pretty much any condition.

goodluck.