Due for engine rebuild? What's worth upgrading? Sensible budget?

I tested compression after a breakdown and had been sitting for quite some time. Results not perfect...
#1: 145
#2: 145
#3: 125
#4: 140
#5: 135
#6: 150

I've only just started driving it again. (Strictly weekends) So, I'd like to test again to see if they've changed at all, but might be moot as I've been lead to believe it needs a rebuild anyway...

Just for a baseline, it has:
stock auto turbos - 15psi
stock fuel system
larger side mount intercoolers
3" stainless exhaust + hi flow cats (I want to replace)
nistune, turbosmart boost controller, turbosmart recirc valves
twin pod filters (might downsize to single or stock airbox)
lightened chrome molly flywheel, balanced ally front pulley, ally prop shaft
ceramic clutch, rebuilt transmission, ally radiator

So the question is, when the time comes, what's worth upgrading? What sort of modern turbos out there? I see people can squeeze larger turbos with aftermarket engine mounts?

Any mandatory head work? (oversize valves, porting?) forged pistons? rods + crank? Worth going to ethanol? I assume would require new ecu + complete fuel system $$$

Getting carried away / diminishing returns? I assume there is a popular sweetspot for budget mods?

 

The question is.
What do you actually want to do with more power?
Which leads to additional questions, one of which is.
What is your budget?

 

Thats the problem... I don't have specific goals and its purpose is not strictly defined.
i.e. I'd like to dabble in drags, do a few track days every year with street use on weekends when I'm not riding my motorbikes.
Budget is also an unknown... Not sure what I should realistically expect to be spending. Turbos and other fancy hardware can be very expensive, I assume would be a large chunk of the budget.
Sure, I could dingle berry hone for free plus cost of pistons, rings, bearings and gaskets... but its a lot of labour so may as well add to it while I'm in there.
I really don't know what would be sufficient amount funds. I see unique autos have motors to order, but they are $10K+
Doing my own mechanical work would save some costs, but labour for machining would be unavoidable.
Again, not really sure, but I was expecting to spend a little more than half that... So you can tell me I'm dreamin'...

 

Expect to spend $5K on hardware for a rebuild to oem specs, then you should allow a few grand for the machine shop (if you want it done properly) after that 'the sky's the limit' (even if you provide the labour)

No matter what sort of power you end up with, you'll still need to spend thousands on suspension and handling to be able to put any of it to the ground ........ then you need decent tyres (one set for road, another for track and a 3rd set for the drags) and none of them will last very long because that's what happens with sticky tyres. Then because you are flogging the zed at the track and drags you can expect drastically increased wear and breakage !!!!!

Do you see the trend that's emerging here ?

If I were you, I'd continue to drive the zed as it is (those compression numbers are pretty good for a well used zed) and get some of the suspension/handling sorted while you determine what you really want from your zed (and what sort of dollars you are prepared to throw at it)

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Actually, I've just fitted brand new tein flex zed coil overs, adjustable camber arms front/rear, adjustable rose joint castor rods, all new tie rod / ball+socket ends all around. Some metal spacers under rear sub frame/diff to aid in anti squat or something, new brake rotors + pads and bridgestone RE003s. Plus probably other things I can't remember just now. A few bushes replaced as well. Probably a few other things I cant remember... Though I would like to get LMGT2 wheels and rebuild the power steering + rack sometime soon.

I didn't mention this as I didn't think it was relevant to engine mods, but I guess its all part of the package.

 

Sounds like you don't really have a budget and a lot of spare time on your hands. What RWHP are you looking for? What about water Methanol injection. Sounds like you still want to be able to drive the car on public roads as well as drag it? That limits to some extent what mods you can legally carry out. As Mike says get a second engine and rebuild it at your leisure to whatever specs you want. Lots of options.

 

I guess I have a loosely defined budget (maybe no more than say 8 grand?) but I could spend way less or more if need be to get the job done. As for power goals... more than what I have now. Was last dyno'd at 245 rwkw. It seems torquey when on full boost which is ok. But it feels like its really lacking top-end.
What sort of power figures should I expect with that sort of money? What would be the mandatory parts needed for a good foundation? (Not wanting to re-buy the same but higher spec parts if I want to upgrade again in the future).
I wasn't sure if I wanted to get another donor engine though. I'm in no rush. I was thinking maybe starting the build next winter. For now I guess its more about just doing my homework and getting an idea of what I need to expect in regards to what needs to be spent, what are just 'nice to haves' and what sort of results I should expect. Even though I didn't have any power goals from last time I had it tuned, I was a little disappointed that other people with less mods were making more power...

 

Re:
"I tested compression after a breakdown and had been sitting for quite some time. Results not perfect..."
#1: 145 This cylinder has lost 26psi.
#2: 145 Same as #1.
#3: 125 This cylinder has lost 46psi.
#4: 140 This cylinder has lost 31psi.
#5: 135 This cylinder has lost 36psi.
#6: 150 This cylinder has lost 21psi.

The acceptable maximum difference in pressure between cylinders is 14psi.
You have 25psi.
Based on those compression readings, the motor is cactus it requires a rebuild no matter which way you look at it.
Sure you can continue to drive it, but it won't be running efficiently, is down on performance & will be costing you money in fuel.

The only logical reason to continue to run this engine would be to keep the vehicle on the road while you save up to have it rebuilt or to find a replacement engine.

If you rebuild this engine to stock configuration the increase in performance will be dramatic, plus you will have the reliability.

You mentioned motorbikes.
Would you take an R1 on a trail ride?
Unlikely, the point being if you want a Z32 to be a weekend street car, an occasional track & drag car.
It will not be suitable for any of those purposes, there will be a compromise in the handling, comfort & braking across the board.

On the subject of budget.
Add up the cost of what you have already spent on your Z.
It may surprise you.

It may prove to be a cheaper option overall, to purchase another vehicle for a specific purpose rather than try & adapt your Z to be proficient in three different types of use.

If you go back through the threads on this forum over the years there have been numerous members that have modified their cars for more "performance".
Where are these cars?

 

You say 'dramatic'... So after a basic rebuild back to stock compression, are you saying that I could recover 18% of lost power?
(tested compression 1 + ~6) / (171 x 6).
So that would take me to 280+ ish rwkw? That would seem noticeable. Plus it really drinks fuel and judging from how grubby my intake plenum is, I assume its getting a fair amount of blowby. Not smoking though fortunately so I think oil rings are still ok.

Regards to the suitability of the zed... Thats a pretty harsh pill to swallow. So if it can't do track, drag or weekend shenanigans... what can it do? It's awful to drive in traffic every day. Can only take 1 passenger and will get covered in dents if I take it to the shopping centre car park lol.

As for adding up how much I've already spent on it... I don't want to know... lol. The logical thing to do would be to get rid of it and cut my losses. But I love the zed and I don't think I'll ever build another sports car after this one...

No idea what's happened to other peoples modded zeds over the years. Sounds like a "where are they now" of washed up B movie stars. Is what the z32 has become?

 

But is that enough to have fun? I'm not a pro driver, competing in any events or trying to be competitive at the drags...
At the end of the day, its just to have fun. I've gotten just a little bit used to the current power output... I can definitely tell the old girl is missing something in top end.
With a bit more power, I think it would be a lot more enjoyable to drive. Will become more challenging to drive, yes. But I think thats half the fun.

 

No improvement with that budget !

You will be stuck at that power level unless you 'up your budget' …….. BUT, a rebuild will vastly increase your low and midrange torque, which will make your zed much quicker in every situation anyway (and a lot more fun to drive)

p.s I see NO mention of injectors ! I would suggest fitting larger injectors as mandatory as part of any rebuild

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Well, I'm an idiot... that was compression tested cold... I'll test again on the weekend.

So if an 8k budget doesn't cut the mustard, what would you be prepared to spend and what sort of power targets would you expect?

Injectors - yeah, thats pretty much a given. I assume they're nudging towards full duty cycle at 15psi boost. I should probably look into how I can download the maps off the nistune sometime soon. I would have assumed injectors would be one of the last parts to be selected?

 

If you are going to put all of this money, time and effort into improving/upgrading your engine what about the brakes? Yes you have new rotors but Z32s were never renown for their braking performance. Get some Brembos or Wilwoods fitted. You have 1500kgs of car that you have to stop and the faster you go the less time you have to stop. Just a thought

 

As I understand it, I can't fit larger rotors under the standard 16" wheels. Though I've read that there are bigger OEM options, like from the newer zeds and skylines etc. I also understand that this will require engineering, and that may make me ineligable for club rego soon (needs to be as close to standard as possible). (Not that they'd notice internal engine mods)
It's on my wish list, but until I fork out money for wheels, I don't think I have a lot of options. However, since my last few laps at eastern creek, the brakes seemed to hold up fine. I didn't have any issues or experience any brake fade... and thats with stock rotors too (non-drilled/slotted).

 

The Z32 is a fantastic sports car in stock form.
If you rebuild the engine to stock specification it will provide hours of enjoyment for years to come & be reliable.
The Z32 is a sports car designed for everyday use.

How are you going to use additional horsepower on the street?
What are you going to do with it?
Please give an example.

If you want a good track car, buy something like a used Renault Megane RS, they're cheap as chips on the used car market & probably end up costing you a lot less than modifying your Z.



You're into motorbikes, if you want to go fast at the drags get a used Yamaha R1, Hyabusa or something similar.

 

I cant stand using the zed every day. other drivers don't see me due to its low profile silhouette. Heavy duty clutch isn't much fun in sydney traffic. cost of insurance skyrockets, and soon to be club rego, it will be strictly weekends on a log book. I daily a pos suzuki swift. manual. will probably replace that later for something more comfortable in sydney traffic.

For the additional power - it would be for snapping braps on roads like old pac etc. To the speed limit of course - law doesn't dictate rate of acceleration Not that cops would know how to define it, let alone measure it
Renault Megane RS? Dude... ... ...
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Its FF... and they're not cheap. I'd rather spend 15 grand on the tired old zed than replace it with a renault. ... Infact, i'm almost offended

BTW, I have 3 bikes. All of which are faster than the zed. '93 gsxr1100, '91 gsxr750 worked up to 907cc, and a cbr250rr with heavy engine mods too. A 250 still keeps up with the zed... How can I let that stand with me?

 

Renault currently owns 43 percent of Nissan while the Japanese car maker has a 15 percent stake in its French counterpart.
Carlos Ghosn, is the chairman of both companies.