I own a 2004 G35 coupe with 140,000. When I got the car it barely ran and had a bunch of problems. Since then I've put a lot of time and money into the vehicle. I plan on keeping this car forever and eventually converting it to a track only car.

So far I've put the Z1 plenum spacer in, a Z1 crankshaft pulley, a HKS dual exhaust, DC headers and a lightweight flywheel. The car is a lot more responsive and fun to drive Compared to stock but of course I want more.

I want to get the motordyne art pipes, an intake, the 75mm throttle body and the aluminum or carbon fiber driveshaft.

My question is which intake is best? I've heard the 3.5 or 4in intakes make the most power but need a tune. I've been looking at the Takeda kit for around $280. Is it worth it or should I get the 3.5inch. Also I do plan on getting the Osiris tuner engine management system at some point.

I want to rebuild the engine or maybe even buy a low mileage one and build it up. Which components are prone to breaking due to high HP and TQ. I want to keep the engine NA and go with high compression pistons. So second question is what does a parts list look like for an engine rebuild/upgrade (say stage 1)?

 

Your point of restriction right now is the stock catalytic converters, they're the single most restrictive point on the entire car and you DEFINITELY need to replace with something higher flowing (personally I recommend the resonated Fast Intentions RHFC) but the stock ones gotta go.

That and a tune should be your next step honestly, you'll probably pick up 20whp. However the 75mm TB with the 3.5"intake WITH THE TUNE will gain even more but you're looking at some fairly expensive additions doing it all at once and it sounds like you're doing your upgrades over time.

1. HFC or TP and tune.
2. 75mm TB 3.5 intake and a retune (lot cheaper since you will already own the cable and license for UpRev, make sure you are actually buying the license though).

The difference between a 3.5 and 4" intake is almost immeasurable regardless of what the "internet hype video's you see about the 4" intake" says about it. There's a reason you will have a hard time finding an honest comparison dyno between the two. Basically it comes down to whichever you find for a reasonable price. I don't think the Takeda is a 3.5" intake? Normally you see the Admin Tuning 3.5.

EDIT: Do the propeller shaft whenever you want, it's a gain you can feel, easy to install, obviously no tuning required. I'd stick with the aluminum because it's a LOT cheaper and you get better bang for your buck investing the money elsewhere.

 

As for the rebuild, there is absolutely nothing on the stock motor you will break with a naturally aspirated engine. Even the MOST BUILT NA's with ITB's are never going to create enough power to worry about rods bending or anything like that.

400whp is the breakpoint where you need rods, gotta go forced induction to hit that.

I recommend the HR gaskets and dremel cutting out the notch needed for proper flow (super easy, look up a video or guide on it) when doing a rebuild. The rest of the components are just your basic bearings/gaskets/water pump/blah blah. Once you measure out the bearings and see what you need just order the correct size ones from Nissan. Fel-Pro always makes good gaskets, you should replace the motor mounts with some urethane ones while the engine is out. Lot easier than doing it with the engine in the cradle. New timing chain/tensioners/pulleys. Reuse the cam actuator solenoids but you need to disassemble and clean them out good. Probably put new injectors in unless you can flow test/clean the ones you have. Get a new knock sensor AND THE SUBHARNESS since they're cheap and probably won't last another 100k.

DEFINITELY replace your O2 sensors with new ones, after 100k on them they will have a delay even though they're "still working".

It's not cheap doing a proper rebuild on these things but mostly because there's so much peripheral stuff to replace beyond just rings/bearings/gaskets.

 

Funny you mention Fel-Pro, I just replaced my header-to-cat gaskets because the old ones fried up on a 2 hour 80-100mph travel. When I did the headers I replaced the O2 sensors and when I bought the car the stock exhaust was basically missing half of its components so i've replaced those O2 sensors as well. I was 100% looking to get the Motordyne ART pipes, they're undoubtedly the top recommendation for G's and Z's. I've hear that they lean out the AF ratio though and that you really need to get a tune before you drive the car WOT.

Also I've gone through the Z1 website multiple times wishing I had a few K to just drop at once but like you mentioned its more of a piece by piece build. I want to do the Z1 motor mounts, transmission mount, rear differential bushing, and subframe collars. Seeing how each of these components are a few hundred a piece I can get them one at a time and not break the bank (being a college student and working full time while finding time for rest is nearly impossible). But thank you for the input, I really need to get the Uprev engine management on my ride, it's one of those things many people overlook but makes or breaks the car. Maybe Ill just buy the cipher cable and then the $300 standard license so I don't get whacked with the whole $500 at once. I'll keep my eyes peeled in the forums, I know I've seen one on here before.

 

I have the Z1 engine/trans/rear diff mounts. I recommend all 3 but if you're going to piece it together start with the rear diff since yours is probably 100% shot if it's still the OEM rubber one.

As for the ART pipes... if you're doing the entire exhaust at once and you know you want test pipes then those are your best option however I've been using the Fast Intentions RHFC on the stock coupe exhaust and it sounds great. I used to have the FI traditional exhaust but even though it was pretty much the quietest option for a true dual exhaust it's still pretty damned loud and no longer had that awesome sexy G35 coupe sound. The FI RHFC on the stock coupe exhaust sounds amazing, just a little louder than stock with zero rasp/drone. It's worth sacrificing the 10whp or so imo. If I want to go faster I'll just supercharge the thing anyways since the bolt ons are pretty limited as far as actual power increases go.

Actually scratch that, if I want to go faster I'll just buy another Camaro lol, super uncomfortable though.

 

I basically have the whole exhaust system aftermarket except for the catalytic converters. I have aftermarket headers, they're not Tomei or anything to brag over but they are less restrictive than the stock manifolds that's for sure. At one point I had resonated test pipes along with my HKS dual exhaust but it was way too loud and very raspy over 3K but it did pull like a mother freaker. That's why I put the cats back on. The HKS exhaust is pretty loud itself but has a deep sound at idle and low RPMS, when I put the headers on it made it deeper and a little bit louder as well. I should take a clip sometime for the comparison. I probably will when I get the ART pipes. Since the resonated pipes I tried were way too loud I considered HFC but the consensus for best sound and power has been the ART pipes hands down.

I've heard the rear diff goes very fast and considering I have about 140K on the car I'd say yeah they're shot but I've never crawled under to actually take a look. The cars only had 3 owners, the original was a mechanic actually and he took care of the car but the kid that had it before me only owned it for 6 months and beat on the thing hard, managed to lose his license in the process so I took it off his hands (his father actually owned it and didn't want it around anymore).

Have you ever changed your diff fluid? I've been wanting to but have been putting it off, Maybe I'll do it when I get around to the bushing.

 

Rear diff fluid is about a 15 minute job including getting the vehicle on/off jackstands. Definitely recommend it if you don't have a service record for it. If you've never done it before it might take you 25 minutes tops, definitely no longer than that. The rear diff bushing makes a pretty massive difference on these vehicles if you're comparing a worn out rubber OEM vs. new poly bushing, Initially I didn't think it would make as much a difference but I was totally wrong, mine wasn't even 100% blown, it was a MASSIVE difference in feel though..