VK45 vs. VH45 in Z32

[z1 zonly]

Long story (feel free to fast-forward to the questions):

In September, I bought an overheated 1992 300ZX specifically for putting in a VH45, as I had gotten a locked-up one free. I did about all the research I needed to get started, and was about to get it going. Through contacts at the local Infiniti dealer, today I had the opportunity to buy a 2005 VK45DE out of a Q45 (340hp/330tq) and two 350Z 6-speeds for $300. I bought them sight-unseen, but everything works fine. Thing is, I'm almost positive that when the engine is delivered tomorrow, it's going to be a bare longblock rather than a fully-assembled engine (I know, I could wait and see, but the anticipation is killing me!).

Questions:

-Where the HELL am I supposed to be able to find a 2005 Q45 to pick parts from? If that engine is going to be a bare longblock, I will certainly need to find one. No junkyard that I have seen has late-model $50,000+ cars. Are all the latest model Q's identically equipped engine-wise?

-I have not been able to find a picture of a stock VK45DE without the plastic covers on top. I've seen enough to know they got rid of the damned spider, but is the new plenum any lower? Can anybody confirm/deny whether it will fit under the Z32 hood?

-Exhaust manifolds. Are they equal length/tuned from the factory? I was planning on TIG'ing up new mani's for the VH45 anyway, but for power rather than fitment. With 340hp stock, I would hate to go through the trouble of making new manifolds to end up with a negligible power gain (if the stockers can even [be made to] fit).

-Engine management. I was prepared for the semi-straightforward VH swap, but I feel overwhelmed by the OBD-II bells-and-whistles of the VK. Where do I start? Could it be as simple as piggybacking the Q45 ECU to run the engine and the Z32 ECU to manage the chassis? If not, what are my options?

I hate to post n00b questions, but my mind's all over the place. Thanks in advance.

[Mettler]

Why are you even considering a VK engine?

Yes, lets pay WAY more money for a motor that has no improvements, and actually comes with smaller/weaker internals from factory.

BTW the 'damned spider' is an excellent intake manifold and goes a long way to boosting low end torque.

[z1 zonly]

Costs way more? It's 2 years old, extremely low mileage, runs fine, and cost me $100.

Weaker internals? So what? I can live with 340 NA hp (and I'll still have the VH to build for boost if I end up wanting more). Plus it's narrower, which is always good when having to notch the frame rail is a possibility.

Never doubted the damned spider was a well-designed manifold, but it sure is a hassle for engine swapping. No fun to R&R either.

Perhaps my subject was misleading--the object is not to decide whether to swap the VH or VK, it's about what the inherent differences in the motors will mean during the swap, since my knowledge base (or lack thereof) was built around the VH. So, any insight on my questions?

[RichZilla]

-Engine management. I was prepared for the semi-straightforward VH swap, but I feel overwhelmed by the OBD-II bells-and-whistles of the VK. Where do I start? Could it be as simple as piggybacking the Q45 ECU to run the engine and the Z32 ECU to manage the chassis? If not, what are my options?

No need for that. Remove your Z32 ECU. It is not necessary. All you need from the VH or VK ECU and loom are:

fuel pump relay triggerECCS relay triggerIgnition relay triggerStart signal to ECUTacho signal from ECUTemp from VH/VH loom to dashSpeed signal from dash to ECUIgnition and battery power to the new loom/ECUOil wire from new loom to dashA/C signal to/from ECU

That's all I can think of at the moment, but they're the basics anyway.

[z1 zonly]

Excellent info RichZilla. Just to clarify, are you talking about wiring those connections into the existing Z harness and running the Q45 ECU? Is it plug-n-play or will I need to repin the connector? Will it successfully control all the functions of the chassis?

[elwesso]

the VH45 with a chip will put out basically the same power that the VK does, so the 340HP is somewhat misleading...

The hardest part about this is the OBDII ECU. thats gonna make things harder, because the ECU actually cares whats going on, vs the OBDI ECU being stupid (for lack of a better term). OBDI and OBDII cars are completely different how theyre wired up.

hate to be "that guy" but a VK and VH swap isnt going to be much different, theres gonna be things that are harder with a VK but easier with a VH, and vice versa. If you want to go easy, you might as go LS1, if you want to go ballin, you should go VH45.

[z1 zonly]

Acutally, the LS1 is bigger than the VH and is extremely difficult to drop in the Z engine bay (with the T-56, the auto is a different story). Did someone say plasma cutter to the firewall? Eek.

Changing gears here--it looks like the shortcomings of the VK lie in the shortblock, while the strong suit of the VH is its shortblock. With the titanium valves/aluminum lifters in the VK heads and boost-friendly VH bottom end, would it be wise to rebuild the shortblock of the VH and swap on the VK heads? How does titanium compared to sodium-filled steel?

Is there any truth to the VK engine being dimensionally narrower? If so, is it solely due to the heads or does some of it have to do with the bottom end?

Lastly, are the heads even interchangeable? The two engines seem to have very similar decks, but I can't tell by pictures whether or not everything will line up.

I'm still anxious for a picture of an exposed VK45 intake manifold. Just read tonight about its variable intake system--sounds pretty trick.

[ScottJackson]

LS1 bigger than a VH? That's a new one to me. If it's larger in any aspect (other than CID), it may be a hair, smidge, touch, or dab longer than the VH. I would think a lot of the people who put them back into the firewall do so for better weight distribution and because the LSx is normally a rear sump oil pan (unlike the VH.

[z1 zonly]

I won't derail the subject, but the T-56 requires firewall cutting for the bellhousing to clear, period. One of the popular LS1 conversions, KrazeeZX, pushed his entire firewall back 3". The 4L60E will fit with minimal fab (search "Adlashwa" on twinturbo.net for info/pics).

Can't back up my sources on the dimensions, site seems to have been updated.

But again, this thread is going to determine the throughput of my entire project (which I'm extremely anxious to get started on), let's please not get off-topic.

[David Steele]

The LS1 is not bigger than the VH and never was the main reason is because its not DOHC

[RichZilla]

Wes, expand my seemingly limited knowledge on OBDII. To what extent does it 'care' about what else is going on? What does it need to know?

[Tecni]

How about a VK with VH rods? 11% thicker

[SeanDean]

For reliable power, easy tuning on factory ECU, simple wiring and ease of installation, the VH is the better swap.

The VK is a bit lighter.

The VH looks a lil more 'pretty'.

The VK can be made to work with those 350Z transmissions if you get a 2005+ Frontier/Pathfinder/xterra 6spd front case

or a VQ35HR/VQ37HR front case.