Building the Nissan VQ37VHR part 3

In our last segment of building the ultimate NA VQ37VHR, we assembled the long block of our engine.  Now its ready to drop into the 370Z chassis.  We had a lot of help in parts selection from our friends at Z1 Motorsports who make some 370Z specific parts, including their 400hp kit to make this easier as well as some cool parts to solve some unique Z quirks.

Part 1

Part 2

Part 3

Part 4

To get our power to the ground, it first has to go through the clutch!  We wanted to upgrade our clutch and flywheel to make sure we would not have problems down the road.  We also wanted to get rid of the stock 370’s super heavy flywheel to improve acceleration.  Z1 Motorsports makes a great system to accomplish all of this in a streetable package.

We started off with Z1’s lightweight flywheel. The flywheel is machined from a forged billet of 4140 steel. Forging refines the grain structure of the metal and orientates it for best strength. 4140 is a high nickle alloy that is known for its toughness making it ideal for this application. Typically 4140 is found in high performance Rods, Cranks and transmission parts. The Z1 flywheel weighs 14.2 lbs while the stock flywheels is a whopping 26 lbs. The lightweight Z1 flywheel is going to free up a lot of power which would otherwise be used to spin up the heavy stock flywheel which is going to result in better acceleration and throttle response.  The lighter flywheel is also going to take some stress off of the syncos and improve shifting.

The Z1 flywheel has a once piece machined in ring gear for strength and has the proper features for the OBD11 sensors to prevent check engine lights.  In our previous experience with flywheels close to this weight, the 370Z’s auto blip system will not be affected by the lighter flywheel.

The fulcrum on the Z1 clutches diaphragm spring is placed so that a higher clamping load spring can be used for more torque capacity but with a low release load and a longer engagement travel.  This is easier on the engines thrust bearings and the drivers leg.  It is also easier to drive off the line smoothly with a longer engagement travel.

For a clutch disc, we opted for Z1’s full face unsprung hub disc. This gives the light weight, fast response and ease on syncros of the solid hub without the aggressive engagement characteristics of the typical ceramic metallic pucks usually associated with solid hub disks. This should be perfect for the anticipated power level of our NA engine.


  1. Yaaaasssssss!! Loving these updates!! Since IAT’s are so susceptible to heatsoak in this car, do you think moving the mafs or possible running a different IAT sensor just after those filters would be beneficial?

      1. interesting. so with uprev/ecutek etc. you can disregard the scaling or just tune to not pull so much timing?

  2. Long time listener, first time caller 😉
    Surprised you didnt go for long tube headers since you are ditching the cats anyway? Well documented power and SOUND improvements to be had there. Also those intakes are very long, no detriment to power having the inlet tract so long?

    1. We know long tube headers are better for power production, but that’s not what the car owner wanted. He wanted to be able to put the cats back for street use.

  3. Street use, but un-sprung hub. What a mashup! You mention un-spung hub being better for synchros. Why do you figure that?

    1. I guess it’s because the disc, which is still connected to the input shaft via splines is lighter and can change rotational speed easier with less inertia. Got it.

  4. Did you guys notice a lot more NVH from the gearbox with the unsprung centre?

    I did a CD009 conversion on my SR20 and initially had an unsprung twin plate. Due to the relatively large backlash in the gearbox the off acceleration chattering of the gears was insanely loud. Changed to a sprung centre and majority of the noise was gone.

    1. I know about the noise because my twin disk solid hub clutch on my Z is awful in this regard. In this case it isnt so bad.

  5. Did you notch the bumper beam, and then box it back in? It looks like it, or Howard is just darn pure magic. It wasn’t called out in the article.

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