I have a 90 300zx.Should i upgrade to vg30det?how hard is it?if i get jdm would i have to switch anything else

Question

my motor is ceased and pistons are blown. should i just get a JDM- vg30de?

Answer 1

There is no difference between a JDM and a US VG30DE (both NA and TT).

The only engine that was changed was in 1996 here in the US when the switch to ODB-II made Nissan run around looking for a solution to pass emissions for the VG30DETT (only the TT, not the NA). So they changed the Variable Valve Timing and decreased the power to 280 BHP. Nissan never admitted that until later on.

If you have a NA Z32 (300ZX), you do not want to do a TT conversion unless you have at least $10K in your pocket ready to be thrown to the conversion. And it is NOT an easy job, nor it can be done by just anybody. You need to know very well the VG30DE and the Z32 itself.

You can buy a short block (just the block with pistons, or a long block (same but with the heads as well) brand new from Nissan or a rebuild one from many places like Z1 and Stillen. Price will range from $2K to over $3K.

The fastest way to get your Z back to the streets is to just replace your engine and be over with it. If you wish to upgrade it, you could buy some good NA Headers (ebay sells them very cheap) to gain up to 25 BHP, a High Flow Filter (ebay again) for another 5 to 10 BHP, a light Underdrive Pulley (ebay one more time) for another 5 to 10 BHP, and a good exhaust (do not go to ebay for this, you should buy good quality unless you wish to change it every 6 months) to add about 10 to 15 BHP. Some people do the ECU upgrade, but it gives you so little extra power that is not worth the money ($500-600 for only 10 to 20 BHP).

All those upgrades together plus a new engine that has perfect compression will make a big different if you are used to your old engine. You will feel it like a new car. My brother did what I just told you (except for the ECU), and he is very happy with the results. He can keep up with many stock 300ZX TT and can pass any stock 350Z with no problem. He drives a 90 300ZX Coupe 5 spd.

If you wish on the other hand (and can afford it) to do a twin turbo conversion, then things are very different. In addition to the engine (you must buy a VG30DETT to have the right compression), you have to buy the following (this is just out of my head, there will be more parts for sure):

- Turbos (for a little more money, you can get much better turbos than stock)
- Water lines for the turbos
- Oil lines for the turbos (make sure to have a TT Oil Pan because you need it for the oil lines)
- Air piping (over 10 different pipes)
- Intercoolers (could be twin intercoolers, or front mount but then you need extra piping)
- AC Condenser (yes, it has nothing to do with the turbos, but the NA has a bigger condenser, and you need a TT which is smaller to allow the turbo air piping to pass through)
- Radiator (just like the condenser, it has a different shape to be able to let the piping pass)
- Oil cooler (the NA doesn’t have it, the TT needs it to cool down the oil or you will burn your pistons too quick and you could also increase the cook effect in the turbos)
- Exhaust Manifolds (or headers, you will need to buy those because yours will not fit with the turbos).
- Down Pipes (needed to complete the exhaust)
- Blow Off Valves (better to upgrade instead of stock)
- TT ECU (must replace your ECU or you will not be able to drive the car)

Besides those, you should replace:

- Engine Harness (should be done as yours is old and will brake, but you will have to look for it as Nissan is discontinuing it).
- Fan Clutch (the TT has a two speed Fan Clutch compared to just one speed for the NA)
- Alternator (the TT has a bigger one)
- Transmission (if you have a 5 spd, it might hold on, but a new clutch should be consider, if you have an auto, then you must at least replace it with a TT transmission or it will not last at all, otherwise, convert to manual)

And upgrades would be better for many things:

- Turbos (as I said before, getting stock turbos is a waste of money, instead buy a good upgrade like T28 or better)
- Intake (a dual High Flow Filter is recommended and you will also gain power)
- Exhaust (as with the NA, you will gain power)
- Underdrive Pulley (same as the NA)
- ECU (replace the ECU with not just the TT but already with a better Air/Fuel map like the one from Jim Wolf Technology)
- Headers (if you can afford them at over $2K per set, you could gain a good timing for spooling up the turbos with those, but they are usually good only when upgrading to big size turbos with external waste gates)
- Waste Gates (only if you upgrade to external waste gate turbos and header)
- Blow Off Valves (a must for releasing the pressure, I don’t even consider the stock ones as they are too small even for stock turbos).
- Turbo Timer (to avoid cooking the turbos)
- Boost Controller (a turbo car is not fun without one of those)
- CAMS (if you wish to improve your high RPM performance, you can upgrade the CAMS to either Mild for street high performance, or to real Racing CAMS but you will sacrifice idle and low RPM as it will be rough).

Think about what you want to do very carefully, you Z is down right now, so you can do many things to it, as long you can afford it, and can deal with many headaches, it will be worth it in the end. But if you need it up and running quick, do not go for TT conversion, otherwise, think about renting or buying another car for awhile.

Good luck.

Answer 2

Right hand drive wiring won't work with the turbo conversion. I am preforming a turbo conversion with a JDM japan motor front clip. After market turbos and front mount intercooler and boost controlers and more. Not the job for a back yard mechanic. The vg30de is the way you want to go and you may also want a new engine wiring harness. Good Luck