: 4.6 N* Crank shaft / oil pump question

09-06-11, 06:41 PM
I have a 4.6 out of a 1999 STS. I studded the block using the kit from northstarperformance. After about 12000 ml it sounds to have a rod knocking.
Now I am looking at a whole lot more fun :(
Anyway when taking it apart I noticed that the crankshaft is grooved a little where the oil pump sits. As I do not have a new crankshaft to compare this to and dont really want to buy a new one unless necessary I am wondering if this is normal machining for this crankshaft? The groove looks to be about a few thousandths deep. I have attached a few pics. Hopefully you can see what I am talking about. Any advice would be appreciated as again I am not looking to buy a new crankshaft.



09-06-11, 07:14 PM
I'm no expert but that can't be good. Someone correct me if i'm wrong but such a groove would need a new crank

09-06-11, 07:25 PM
Looks like the harmonic balancer bolt torque was incorrectly done during the first overhaul and the oil pump drive ferrule has been spinning on the crank. (That might be the cause of the rod knock.....) You can probably get away with this one. That is not a great load bearing part of the crank - a simple polish with fine crocus cloth, proper torque on reassembly and you're good to go.

Here's the orientation of the oil pump setup.

09-06-11, 09:20 PM
Thanks for the quick reply. One other question. How difficult should turning the oil pump be?
I am trying to turn the oil drive rotor #9 with the oil drive pump spacer #11 and I am unable
to turn it by hand. I would think it would be able to be turned by hand. Now another question
comes up. What drives the oil pump? I assume that the crankshaft turns the oil drive pump spacer
by centrifugal force and then the spacer drives the rotor. I assume this as there is not a gear or shaft
that is turned like the oil pumps in other motors.

Thanks again,


09-06-11, 09:44 PM
The oil pump is driven by being clamped (sandwiched) between the dampener and the rear lip of the crankshaft. That is why dampener torque is so high and is extremely critical when installing the dampener. Too loose and it slips, thus no oil pressure.

09-06-11, 09:45 PM
The oil pump is driven by the crank once the balancer is torqued .The oil pump drive is essentially sandwiched in between the balancer and the crank but only if its torqued properly as Sub said. The pump should turn by hand . I have several extra pumps if you need one its yours for the cost of shipping. Call me at 847 878 5676 Joe @ www.midwestcadillacrepair.com

09-06-11, 10:22 PM
Thanks for the info Ranger and edb150, edb150 I will call you tomorrow.


09-07-11, 01:47 PM
If you have a rod knock.....I'm betting your crack is bad.....ie, if it were a "normal" crank, it would need to be turned....and since turning the N* crank isn't recommended....bad crank.....

Does it knock the same all the time, or does it get worse under load?