Project Leopard RB25det

Project Car Magazine’s M30, Project Leopard, was all about the swap. In great detail, the magazine showed what is needed to swap an RB25det into an M30. After it left Koji’s (original owner) and Jon R’s (who bought it off Koji and later bought it back to save it) possession, the car was truly tested as a drift car (leading to the car being used roughly). The car had a few different configurations until the #6 piston ring land was diagnosed as the problem (Steven took the engine apart). Once the car reached the SR20 store (the original builder of the car from the magazine), I knew Marco (builder) would know what to do and how to approach it (he has been building these types of engines for a long time).

When Marco and I discussed this build, Marco said he would help me BUT we can’t use cheap parts. No Cheap turbos, knock off parts or Freddy manifolds. Quality parts from established companies.

I always weigh option of buying another used motor or rebuild with upgrades. I decided with rebuilding with upgrades (to make a new motor to be stronger) would be best as I could replace a lot of older stuff on the engine, but also address some of the issues that come with the RB25det.



*I am not a drifter or drag racer or seeking massive HP. I went with upgrades because I also want the car to be strong and reliable. BUT the point is to rebuild this car. That includes the RB25det. 

Missing items

When Jon R. bought the car again (he originally bought it from Koji years ago) he went on a mission to try and track down mostly everything that was on the car that was originally on it. While some of the items he couldn’t find (ARK turbo timer and boost controller, Trust down pipe), he got almost everything. When Jon sold me the car, I asked him what was missing and he gave me few things off top:

  • RB25det transmission
  • Greddy Intake manifold
  • OEM Exhaust manifold
  • Turbo

Marco said he has an RB25det transmission that he has checked.


Jon R. was able to save the custom items for the RB25det transmission. The custom transmission mount and professionally made driveshaft. These were shown in Project Car magazine.


Next I had to get an intake manifold. It was hard trying to navigate the cost honestly. There are Freddy manifolds  (Fake Greddy) for pretty good prices. Marco being in LA, being part of the Import industry and being a reputable shop and even connections to Greddy, there is no questions that I can’t use a Freddy manifold.

I was able to get one used and in good condition.


When the Greddy manifold was received, Marco noted that the upper radiator insert was damaged.

I ordered one from Boost Doc in Australia


I didn’t know much about the exhaust manifold and asked Marco what he thought. He regarded the stock exhaust manifold was the best because it is cast iron and typically wouldn’t crack. He also said he’d like to get one with the heat shield.

While this is out, I decided to have the exhaust manifold heat wrapped and have the heat shield cleaned up and ceramic coated. I feel reducing radiating heat is a good thing.


I also got Nubis/Raw Brokerage exhaust manifold studs.


Tomei metal exhaust manifold gasket




The turbo Marco said to do with was the Tomei Arms MX8265. It is a straight bolt on upgrade. I was trying to find something cheaper as this turbo was double of what I budgeted for. I realized that I needed to bite the bullet on this one as I didn’t like what was out there. I didn’t want used and I didn’t want rebuild.


To keep the heat with the turbo, I’ve decided to get a turbo blanket.


One of the issues with LHD cars and these motors is the steering shaft. In the original builds, they used a Syko Performance elbow, which goes around the steering shaft.

Addressing the RB25det oil issues

Once you start looking into RB engines, you will find some common problems. Many RB engines used in motorsports would throw a bearing. Often the oil goes to the head and doesn’t drain fast enough.

There are a few ways to address it and they all work together. I don’t think I will be drag racing or drifting too often if at all. But I still like to have issues addressed while the engine is out. Easy install is an oil restrictor in one of the oil galleries. I used a Tomei one.


I got a head drain kit. This one was from Franklin Engineering with drain hose and a bung welded onto a new oil pan. The oil pan that came with the car had been damaged (pushed in) from who knows what.


I also got a set of Nubis/Raw Brokerage oil pan bolt kit


Another issue is the crank shaft and oil pump contact surface. Often this leads to oil pump failure especially in high engine revving. A new N1 oil pump is installed.


and a Nitto crank collar has  been added at the machine shop.

Machine shop

My approach to rebuilding old engines is to always have components checked at a machine shop. This engine needed it regardless since it was the piston ring land that failed, most likely scathed the the cylinder wall. Which was confirmed and solved. Block was checked for tolerances, cracks, cleaned up, new freeze plugs and started to get assembled.

Other components were checked and assembled there. Crank checked and then added crank collar. Head was cleaned, polished, and assembled. Cams checked and. Valves checked and installed new Tomei valve springs.


Tomei valve springs


  • CP pistons and rings
  • King Bearings – rod and main
  • ARP head studs
  • Tomei head/intake/exhaust manifold gaskets.
  • OEM camshafts – checked
  • Franklin Engineering Billet alloy Cam covers seals
  • Phase2 clear cover
  • Nismo clutch disc, pressure plate and flywheel
  • RB25det Throttle body (replace Q45)
  • RB25det TPS
  • OEM timing belt and idler tensioners
  • N1 Water pump
  • N1 oil pump
  • Nismo thermostat
  • RB25det Rear main seal
  • Nubis Exhaust manifold studs (raw brokerage)
  • Nubis Rear main seal bolt kit (raw brokerage)
  • Nubis oil pan bolt kit (raw brokerage)
  • Phase2 Cam gears (blue)
  • Phase2 pullies (blue)
  • Phase2 Fuel rail (blue)
  • Nismo 750cc injectors
  • Trust Downpipe
  • Grex Oil filter relocation kit
  • Trust Oil cooler



Another item took time to decide if I wanted was the coil packs. My friend Denny mentioned it in a conversation and I decided I wanted to upgrade my coil packs. I kept debating what to get and why… finally, I decided to go all out and get R35 coil packs.

The set is from Platinum Racing Products in Australia. R35 Hitachi coils packs (OEM) with PRP’s billet aluminum bracket (in blue). Wiring Specialties harness. I also ordered a 5 point grounding kit from them.

Alternator upgrades – Still waiting

One thing that I’ve ordered and still waiting for is the alternator upgrades from PRP.

It consists of a bracket and an adapter bracket and pulley to run the LS V8 alternator that is 140w


Clockwise Customs’ adapter bracket:

It was over a month and I decided to ask PRP USA what is going on.


There are a few things left for the engine bay in general.

I want to have an oil cooler and oil filter relocation kit. We still have to see clearance for either stock clutch fan or electric ones are need. Radiator and intercooler have to be measured and mounted.

While there were a few things I wanted to add or change, the motor is assembled, so some of the items could not be added.