In general the inline 6 is supposed to be one of the smoothest running engines with the second being an inline 8. Something to do with the harmonics of the internal rotation. As for specificly the Z engines the V6 makes more torque while the inline gives a good balance of hp and torque. For instance on most modded VG's you'll see the torque is much higher than the hp where as the inlines of the 70's show similar numbers for both hp and torque. The main issue I have with the V6 of the Z31 non turbo is that it doesn't respond to mods to well becuase the engine is already pretty good from factory. While the L series engines are also good from factory they can also gain a lot from mods. It's not uncommon for people to hit 200+ with the inline 6 but you'll rarely see anyone pull more than 180hp with the VG n/a. I'm not clear why Nissan went with the V6 when they did as I'm not clear on that part of the history of the Z. With the technology they had back then they could have easily stuck with the L28 to produce the same hp and for the turbo version stuck with the inline 3.0 that they had in Japan (300zr). Basicly if you take an L28 block with flat top pistons with an N47 head the compression will be upped to about 10:1 and will increase power. So with a simple head and block combo with a little revamp on the cam and EFI system they probably could have made the same or more hp engine than the V6 that was produced in 84. For what ever reason Nissan switched and probably for better reasons, who knows. What I do know is having both my L28 in my 280z and my VG in my 300zx I would much rather drive, mod, repair, tune up, etc on my 280z than my 300zx. I'd rather see the RB inline in the 300zx than the VG they put in. I'll even argue that Nissan should go back to an inline 6 design for the 350z than increase the displacement of the VQ they are currently using. If you look over on the 350z forum some of them are wanting Nissan to go with a 4.0 V6. No thanks, I'll stick with my old Z's
The L6 series is much easier to work on, but that goes for just about any inline 6.
Nissan claims that the VG30 is 21kg lighter than the L28E and 10mm shorter than the CA18.
Neither engine is particularly tolerant of bad cooling system maintenance, although the shorter water path from front to rear cylinders of the VG30 should make it less intolerant.
A VG should rev with less effort. The crank is shorter and lighter so torsional vibration is less of a worry, and the oversquare design helps, too.
Less main bearings means less friction.
You should not need berserk revs with the VG since it was designed with boosting in mind.
The L28 gets upset with big revs and the factory harmonic balancer might be the first thing to fail. Even the first L24s had concerns.
What do you want to hear? Which one makes the most power for $$ spent?
The VG motors were the first mass produced V6 in Japan.
Nissan was thinking ahead somewhat. The compact V6 shape allows it to be fitted to many differnent models, and allows it to fit into a FWD config as well.
BTW, the JDM-only 300ZR used the early version of the VG30DE engine which was subsequently put to good effect in the Z32.
The RB engines are nice devices but are quite large lumps, too.
Why do you say the L series doesn't like to rev? The L series are very well known for being high reving engines. Yes the harmonic balancer can be an issue but the stock one is good for up to 7k rpms. Perhaps if you are constantly racing the engine going over 6k then you might consider a harmonic balancer upgrade such as the BHJ version. Still plenty of people are reving 7k+ with their L series.
I didn't say the L series does not like to rev, I referred specifically to the L28. A long block and crank along with oversquare dimensions create their own potentially bad vibrations which have to be taken into consideration.
You can spend all sorts of money adding aftermarket parts. The L series has enjoyed a particularly active aftermarket and the VG does not, which may be partly a result of the emission regulation regime each engine was designed for.
The original poster did not specify any particular area of concern, so what are we comparing, stock engines or modified engines? How modified?
The L engine in general is actually quite a rev happy engine.
With the right mods, they can be made to rev to 8k. It is at 8.5k rpms that they suffer from bad harmonics. Inline 6 engines are the most balanced engines second only to v12, which are almost two L 6's put together.
As far as engines go, the L series is known for being quite bullet proof, the downtime of many Z is caused by 30 year old electronics, not a blown engine.
There is a lot more room in L engine bays, and its actually nice to be able to see the ground on both sides of the engine. I have not owned a z31 or z32, but I have heard that both of the engines bays are extremely packed and require much more effort to fix some easy problems. (Like the knock sensor on the z32).
All in all, they both have there pros and cons. Stock for stock I would bet the 300zx is a little better because of improved electronics. For modifying I have heard the L series is much easier and forgiving. The plus side is that I like 1st and 2nd gen body designs more then any other Z, but I'm biased
If it comes down to reliability then both engines are quite solid.
Which one the OP would want to use depends on many factors, some of which may be involve the level of modification desired and what car the engine might go into if not the original.
All I know is I like the VG motor better and yes I've also had both. Its easy to see that NIssan went with this motor because of the size and power it creates. The Vg on an engine stand is actually a tiny motor compared to most six cylinders out there. I saw it last weekend inside a little datsun 210 and it just wowed me at how small this motor really is. Awesome power too.
Actually its a 300hp motor, not a 400hp. While 300hp out of the SOHC VG is pretty good it's a complete race motor and wouldn't run very well on the street. Not to mention the compression is up there so that it requires race gas. Basicly it's not someting that most of us could use even if it was affordable. It's more for people who are into SCCA and such that want to stay in a non turbo class but need high hp. Yes the lack of aftermarket support doesn't help but even if there was people making parts the SOHC still wouldn't be producing high numbers. At most while staying streetable you could probably get 200hp to the rear wheels with a fully modded street 300zx. While thats still good it's not exactly a lot, especially for the weight of the car (3000+lbs).
As for question So a stock L28E in a Z31 body would suck less?
Yes and No. No in the fact that the last L28 that was in the 280zx only produced 149hp at the crank so it's 11hp less than the 300zx and probably about 15-20 less in torque. However when you couple that motor with the better EFI system that is on the 300zx the hp should match the 160hp if not more. The stock EFI on the older Z's really did suck. Also Nissan could have easly stuck the 280zx block with the N47 head on there to raise compression. That motor with the newer 300zx EFI system could easily put out more hp than 160. Also it's not uncommon for L seires engines to be past the 200 mark in non turbo form. We could go back and forth on this but as someone pointed out already Nissan went with the VG for more than just power reason. As mentioned it was becuase it could go into to other cars for different drive combinations which means Nissan could save money. No matter what I still love my 300zx.
I am aware a certain datsun tuner out of cali that I am not going to mention. That I know and have proof of building a L28 with 310hp at the crank on a P90 head, tripple mikunies(spelling?), and L24 rods(2.9L). Oh and its N/A.