Not sure what to do with my 300zx

[Jayden]

So I have a 1991 300zx Z32 Twin Turbo ... it is an right-hand import with BC (Canada) VIN's and registration and the whole nine yards, as well as the confirmed 'Fairlady Z'.

It is in 9/10 shape, I got it for $3500.00 CAD and now it's mine, however... it has a noise!

I've taken videos and recordings, sent them to local Nissan geeks, posted them online, etc. and I have gotten quite a bit of feedback, some HAVE said that it's a rodknock, but others who have owned similar cars, with similar situations, say its too "consistent" and there was another attribute I can't remember off the top of my head. However, most feedback has been leaning towards a spun connecting rod bearing, and the way it almost sounds like a spinning rattling, I believe it is as well.

I am committed to the task of keeping this vehicle. I would love nothing more than to make it the way I want it over time. I don't know anyone who owns one of these, and I live in a somewhat middle-class medium-small town. Where would I even look to get replacement rod bearings that are OEM? Is the job itself more than meets the eye? Am I better off parting the thing out?

I need guidance.

[Ace2cool]

If the rest of the car is in good shape, a rebuild would be the way to go for sure. Once you get down past all the accessories and peripherals, it's a standard V6 engine. Anyone that's rebuilt an engine can rebuild this one as well. Just follow the FSM and you'll be fine.

[DCaff300ZX]

I agree with Ace, rebuild it. The FSM is great help, but also if you can find a Z32-specific or at least Z32 knowledgeable mechanic that's a huge plus as well.
LOTS of good vendors and parts aren't too hard to find, just a bit costly compared to many other cars but well worth it.

[nissanfreak12]

Are you sure its a rod knock and not the cam gear/vtc rattling? Is it coming from the top end or lower end?

If you want to find out there are a couple ways to find out if its rod knock. First, drain the oil. If its from a bearing, you will have metal flakes in it. I don't care if the previous owner changed the oil 30 times, unless he tore the engine down and competely dipped it, it will still have metal flakes, period.

Second, if no metal flakes are found, its not bearings or a knock. But just to make sure, disconnect one injector at a time. Yes, the engine will idle funny, may even die, but if the noise goes away, that is the bad bearing.. If its a main bearing, there will stil be a noise/knock. But, you will have metal flakes in the oil.

Third, if you still have all the noise after the first 2, check the intake cam gear. If the spring is weak it will rattle like a bad bearing noise.

These are just thoughts to check before assuming a bearing issue.

[Jayden]

Are you sure its a rod knock and not the cam gear/vtc rattling? Is it coming from the top end or lower end?

If you want to find out there are a couple ways to find out if its rod knock. First, drain the oil. If its from a bearing, you will have metal flakes in it. I don't care if the previous owner changed the oil 30 times, unless he tore the engine down and competely dipped it, it will still have metal flakes, period.

Second, if no metal flakes are found, its not bearings or a knock. But just to make sure, disconnect one injector at a time. Yes, the engine will idle funny, may even die, but if the noise goes away, that is the bad bearing.. If its a main bearing, there will stil be a noise/knock. But, you will have metal flakes in the oil.

Third, if you still have all the noise after the first 2, check the intake cam gear. If the spring is weak it will rattle like a bad bearing noise.

These are just thoughts to check before assuming a bearing issue.

Thank you for this, this information in itself is more than what I have gotten out of anyone.

The noise is top end, almost coming from the middle-right (if you were facing engine bay) closest to the windshield.

I will do my best.

[Ace2cool]

Could be VTC noise, could be a collapsed lifter. A rod knock can sound like it's from the top, even if it's not. Mine did, and I only figured it was rod knock after I got totally under the car and the noise got louder.

[DCaff300ZX]

Could be VTC noise, could be a collapsed lifter. A rod knock can sound like it's from the top, even if it's not. Mine did, and I only figured it was rod knock after I got totally under the car and the noise got louder.

Agreed with nissanfreak's comments and the rod knock comment, my NA died of a spun rod bearing and as mentioned my investigation covered the VTC's and lifters until those both checked out and after getting under the car, I also decided the sound WAS down low and not up higher. The VTC's are a bit more "clicky" and a different sound than the rod knock which is louder and more of a "thunk" or "thump" sound...oh, and the sound will build as you slowly rev while the other sounds stay more consistent, at least my NA was that way.
Not exactly definitive, but hope this helps.

[Ace2cool]

My rod bearings were actually very different than most. No metal flakes in the oil at all. Also went away when revving. The oil pressure build enough under rev to cushion the worn section of rod. Spun bearings are a totally different animal than what I was dealing with though.

[nissanfreak12]

My rod bearings were actually very different than most. No metal flakes in the oil at all. Also went away when revving. The oil pressure build enough under rev to cushion the worn section of rod. Spun bearings are a totally different animal than what I was dealing with though.

You had to of caught it right at the beginning or the bearings were out of spec. You may have gotten away with thicker oil to buy some time. Did the crankshaft look scored or damaged?

[grayman_TT]

There is a shop that you may be able to talk to that is in BC. Being from MB, I have never used them. Here is their link:
http://www.zshop.ca/

[Ace2cool]

My rod bearings were actually very different than most. No metal flakes in the oil at all. Also went away when revving. The oil pressure build enough under rev to cushion the worn section of rod. Spun bearings are a totally different animal than what I was dealing with though.

You had to of caught it right at the beginning or the bearings were out of spec. You may have gotten away with thicker oil to buy some time. Did the crankshaft look scored or damaged?

Absolutely no scoring to the crank, so I think you're right. I just had a slight knock at idle that went away at anything over 1k rpm. Click my sig and look at em. It's on the 2nd page.

[LIBRILZ]

These engines are prone to rod knock