VQ35HR S13 Sil-Coupe Build

[Jissan]

Goal: VQ35HR Swapped S13 Sil-Coupe 240SX "Zilvia" - Autocross Build

SPOILER: I just end up drifting it.

I've been putting off starting a build thread for the car since I wasn't sure I'd be able to keep it updated, but I recently saw the value of the discussion these threads promote and decided I'd have to start writing. I also tend to take a lot of pics so I'll have to post multiple times due to the 50 pic limit.

Backstory Garbage

I got behind the wheel of a friend's '03 M3 about a year ago and decided I needed a project car to work on with my son. Being a Nissan nut I settled on a sil-coupe in Cali that needed some love. Coupes are pretty rare in my area, especially with a Silvia front end.

I flew out and drove it back to Louisiana. The KA mileage was unknown but it supposedly had been rebuilt within 20k miles. It had a Sparco / NRG QR wheel, Nismo shift knob, G35 Coupe wheels, Z32 brake setup with 5-lug hubs and drilled / slotted rotors, Dmax-looking tail lights, tired seats, a shredded dash, and a rat's nest of wiring. There was no power steering ( pump was full of iron filings ), neither the speedo nor the tach worked, and the JIC Magic coilovers were completely shot. They were also so low that I shredded a tire on the way back from rub. The AC wasn't hooked up and the 5 speed's synchros were trashed. Included were a set of Z32 wheels with bald tires, a set of 20mm spacers, an extra S13 USDM digicluster, two S14 clusters ( one with white guages ), a rebuilt Calsonic compressor, JDM surfboard LED spoiler, a jack and various extra parts and fluids. All this crap in the car didn't help the ride height on the trip back. I overpaid but karma got me back to my swampland with only a couple minor snags.



Since I bought the car to have fun, I immediately took it to an autocross where I faired pretty well... if you rule out the results... and judge based on enjoyment alone. I got thrown into STX for my racing steering wheel, Silvia front end, larger wheels, and the boat anchor aftermarket coilovers. The tires were garbage and there were some nasty noises coming from the drivetrain. Turned out the RUCAs had bad rod ends and the front right hub sounded like Wheel of Fortune with the car on jacks. I had an absolute blast. I addressed the car's immediate issues, got some KW V3s ( night and day difference ), a set of NT05s ( more night and day difference ) for my G35 Coupe wheels, an Energy Suspension poly bushing kit, and did random enhancements to help me cope with driving the car around town.

Since I had two digital clusters on hand to try to get working, I tried the How to:Repair 240sx digital speedometer with HUD. NICO Club resistor fix on Nicoclub and it ended up working on the JDM cluster... which can't switch to MPH. So I rocked the KPH.






This was about the time I was looking into swaps. I wanted a car to autocross but didn't want to take the fun out of the car just to adhere to strict class rules. I researched all the turbo RBXX(20,25,26), SRDET, and KAT options. I like the cost of KAT, the weight of the SR, and who doesn't love the legendary RB, but I'm not crazy about the weight and I'm not looking to drift ( EDIT: present-day Jason is reading this and laughing hysterically). I ended up deciding that there was enough info available for me to try a VQ swap. After a month or so of looking for a 350Z / 370Z / G35 / G37, a rollover 2007 Nismo 350Z (#120) with 55k miles popped up on Copart. After some research on how Copart worked I could give a class on it, but that's a different thread.

The beauty of getting the whole car, not to mention a limited edition version of the car, is that you can part out everything that won't fit or you don't need. Highlights included Nismo Exhaust, Nismo Rear Bumper, Suspension, Nismo Yamaha Vibration Dampers, semi-trashed Nismo Rays wheels and a lot more crap I have and haven't sold yet.



Hauling off the shell



The Plan

I plan on using as much of the newer or higher performance parts off the Z as possible. I've done a lot of research on most of this but feel free to point omissions or trash out.

Mounts:
I bought a motor and tranny mount kit off ebay that looks like it'll get the job done. I plan on cutting them shorter since I want to use OEM rubber motor mounts and the kit came with solid mounts, and anyone who's driven in New Orleans knows that's just crazy. I'm going to try to keep the motor as low as possible and will still probably need to space out the hood or cut it up.

I looked into different ways I could get the engine lower, since all the VQ builds have the telltale rear hood gap, but the most you'll realistically get is about an inch. You could spend a wad of cash on a dry sump system but the transmission is nearly as low as the oil pan. You could try flattening the lower front oil pan, but it would probably require modification of the the internal oil pickup, and the oil filter mounts just above the pan.




Since I have the VQ35HR, my starter is going to be in the way of the steering rack since it doesn't have the tabs that the DE has to mount the starter on the passenger side of the engine. I'll either need to create an extension to the starter and mount it farther back, tilt the steering rack like PlusONETEN, or (worst case scenario) put spacers under the crossmember like a lot of other members, which apparently will throw off all sorts of roll center. I wonder if there's enough space on the crossmember LCA mount for me to offset the gap by welding the bolt holes closed and redrilling them higher...

Fuel:
The Z's VQ uses a returnless fuel system and relies on an in-tank regulator/sending unit. I plan on modifying the fuel rail setup to use the S13 return system. I picked up some fuel line, an AEM fuel pressure regulator, a 255lph fuel pump, and a couple of fuel rail adapters. Should be a decent setup for nice cool fuel.

Cooling:
The Z33 radiator / AC core / fans / overflow tank assembly is too wide for the S13 so I picked up a Mishimoto radiator and fan shroud kit, ouch. The warranty was the deciding factor in going with Mishimoto.

Power Steering:
I didn't have power steering for a few weeks before I installed a junk yard pump, which died after a couple of weeks from the iron filings even though I flushed the crap out of the system, but I really liked having power steering. Since my rack is apparently trashed from iron filings in the fluid, I ordered a remanufactured rack as well as a power steering kit off VQSwap.com (subsidiary of ChaseBays) to tie the S13 rack into the Z33 pump.

Brakes:
I plan on using the Nismo's Brembo setup, especially since I already have 5-lug with the Z32 calipers all around. In the front I just used the larger rotor and drilled out my knuckles to 14mm (IIRC) with a press. I also got some shorter bolts since the Z brake bolts' smooth shank prevents using the original bolts. The S13 steering knuckles are a good bit thinner than the Z33 knuckles.

For the rear, the bolt pattern didn't match up so it looks like I'll be fabricating some adapters unless someone knows someone selling cheap ones. The S13 ebrake shoes look like they'll line up with the larger rotor's interior braking surface but I've only done rough measurements.



Electrical:
I'm just going to basically put the entire 350Z electrical system into the S chassis. I'll need to interface with various lights, sensors, etc. of course. I don't initially plan on removing NATS or programming the ECU so I kept the entire steering column, throttle pedal, BCM... I've got a fair amount of wiring ahead of me.

Differential:
Of all the aspects of this swap, I think I've read the most on which is the best differential / final drive gearing to use. My current plan is to modify my subframe to take the Z33 differential. I plan on using a Q45 driver's side axle on the driver side, and the Z33 driver's axle on passenger side. There are people that say the R200 4.08 will serve my purposes well in autocross, however this would apparently be horrible for highway use. On the flipside, there are people that say the 3.357 FD out of an automatic transmission 350Z / G35 is an even better choice than the 3.54 LSD that I already have due to the weight difference, but I'm afraid this might be too tall a gear for putting power down.

Aside from the gearing, there are other reasons to go with the Z diff vs the R200 VLSD. One reason is that my VLSD is probably completely worn out and open after all the years this car has seen. This wasn't a huge factor since I could easily just grab another 240 diff, but most that I could have picked up were open diffs. The Z ECU reads ABS, TCS, and speed from the six-bolt output shaft diff flanges ( in addition to the ABS rings on the front hubs, of course ). I would like to have the option to use ABS if so inclined and a working speedo will be new to me. If anyone has some spare front hub ABS rings lying around, I want to buy them, LOL.

Here's a comparison shot I took of the Z and S body diffs and axles. The R200 S13 VLSD has no mounting bushings whereas the Z diff has bushings on the two mount tabs in addition to the rear. The rear Z diff bushing is on the subframe.





Light VQ swap reading:

Near perfect diff for VQ or V8 conversions
PlusONETEN build
VQ 240Z, This guy incidentally is THE resource for shifter bracket relocation

Post-build plans include a race wheel/tire setup: putting Toyo Proxes R888s on a set of RPF1s in 17x9.5, ~12 offset or so... or if I hit the lottery, some TE37s. I'd also like to get some adjustable sway bars to play with but I haven't started looking into which ones yet. Sadly, I also like the Rocket Bunny S13 coupe kit, which sucks, because the kit plus fenders would probably cost more than my KW V3 Coilovers.