450zx rebuild and mod

Discussion in 'Member's Garage' started by accident94, Mar 16, 2017.

  1. accident94

    accident94 New Member

    This post should catch everyone up on the past 6 months.
    So after buying my 450zx, the motor spun a big end. Ouch.
    It ten sat in various places around uni before moving into my garage

    So time for a new motor

    After a bit of research I bought a used '92 vh45. This mainly to do away with the Siamese intake ports, but also has the added benefit of not having to change the timing chain guides, along with the other Gremlins on a first gen engine

    After pulling the engine I decided to do a few mods whilst it was out. What followed was 6 months of stalling and pain.

    My planned mod list was as follows:
    Can regind- stage 3 by camshafts.co.nz
    ITB's. + top mount injectors and fuel rail to suit
    180 degree crossover headers with 3 inch exhaust and cutouts.
    Mega squirt to drive it all
    New front sump with baffles and short pickup
    Extended arb drop links (to make space for sump)
    Tidy up a few things and make a few small changes to other things around the car
    Full aero undertray with diffuser

    As of today all these things are in various stages of completion. The car is back on the road in it's 'stock' form out of neccesity, but I'll detail progress and share my designs nonetheless.

    QLDZDR ID=David

    Is this the Zed that was built and had a mod plate, was running and then .....
  3. accident94

    accident94 New Member

    ITB's + cams

    so starting at the top of the lists.

    Camshafts are pretty self explanatory
    specs are 185? at 050, 272-272? advertised dur, 227? cam lift and 385? valve lift. These specs arent super important by themselves, but they drive a lot of decisions down the line. I also have a spare set of camshafts (if they arent scored) so i can send these off and install them later


    Here's where it gets interesting. ITB's
    all the math and design work comes from my experience with my university motorsport team. it all relies heavily on the resources of that team, but most notable reference is four stroke performance tuning by a. graham bell. If youre going to undertake a custom project like this, i suggest you read it.

    i decided to tune for high rpm, between 4000 and 6000 (peak power and peak torque on the stock motor. The camshaft will probably move the peak power up towards redline and fatten the torque curve but peak torque (the fun stuff) should remain pretty constant

    the parts:
    i chose to use gsxr 1300 hayabusa throttle bodies (2 sets). These are cast individually (so can be spaced out) and have a 42mm throat. they are also relatively cheap.
    You might think they'd be too small, considering they're off a 1.3l bike. Bear in mind that the 1.3 makes peak torque at 7000 and peak power at 10000 rpm. by a very rough approximation, the bike makes 173hp with 4 itb's, so two sets should be good for 346hp. also, the stock runners are narrower than this. given that my target is 400, should be possible. we'll see.


    adapters: This is where the magic happens. the runners between the ITB and the block. These have been through a few iterations now. Inintally they went straight up and down, untill i realised the ports didnt actually go straight in, They were then re designed and re-re resigned to accomodate runner length

    the plan was to 3d print these on a makerbot in PLA and then lost plastic cast them (i.e. invest the PLA part in casting media, burn it out then pour aluinium in). here are some pictures of my first attempts

    (apologies for the large photos, i'll crop them down in future)


    After realising that this wouldn't work (the design, i may still use that process) i redesigned the runners to include the angle, as well as a few other improvements. i also decided to try 3d printing a direct end use part, using glass or carbon re-enforced nylon, or polycarbonate (i might be able to access a 3d printer capable of these materials). The nylon is fuel safe, and handles the underbonnet temps of an mr2 fine. it should also be completely stable for the loads required, even at head temps up to 120 degrees, and should be cooled slightly by the airflow through it. a test peice (3d printed bracket) is going fine after several weeks.

    Re designed parts:
    14962428_191170631339526_106018038_n (1).jpg

    runner diameter is a little larger than what is ideal, but was constrained by the ports and ITB, Length is tuned between 12 and 14 inches, and i intend to make several sets of trumpets to allow me to test the lengths within this range. Plenum (throttled) volume should decrease by about 65-75%
  4. accident94

    accident94 New Member

    Yep that's the one.
    onto bigger and better things, right?
  5. Chrispy

    Chrispy Pretentious Upstart

    Very cool!

    But front sump? Moving the engine forward? Mine was a rear.

    And where are the 180deg headers going to fit?
  6. accident94

    accident94 New Member

    Fuel, Oil and water

    The itb's will also necessitate new injectors (top feed) and new fuel rails.
    Fuel rail extrusion is reasonably easy to come by. I have ordered some from the states.
    the injectors themselves are ls2 injectors, 700 odd CC. They are overly large, yes. but this style of injector has good transient response, so hopefully i should be able to use injection timing as a tuning tool instead of just as a shit shooter for fuel (i.e. inject all the fuel at the ideal time, rather than hose down the entire port)

    This graph helps explain my choices (helps me, at least)

    i dont THINK i will need to uprate the rest of the fuel system (pump etc) but we will see.

    post explosion, the old oil cooler was full of bits of metal, and i didnt want to risk cleaning it. Luckily, one of my friends had one laying around, that also has a thermostat in it (albiet with a big rising sun painted on the front. oh well).


    The filter relocation that was on it will remain, and this hosing makes it easy for me to tee in my bottom end insurance policy: a 1.3L accusump this SHOULD help me not destroy another engine.


    the peice de resistrance in this oil system is a custom sump, complete with baffles, gates and windage. i was going to add a crank scraper, but never got around to it. Sump is 7L, similar size to stock, all made of folded sheet steel with rubber gates and baffles from tomei.

    first some CAD (cardboard aided design)

    Then some CAD (computer aided design)

    Final Product, tig welded up and painted

    This sump requires extended ARB drop links. Currently, my ARB is disconnected and my drop links out of the car for measurement. 140mm (up 40mm from stock) should work and not foul. you can get adjustable ones on fleabay for like 150, but i plan to make my own.

    COOLING: the radiator in this car is a little small for my liking. Will probably get an uprated NA radiator from PWR, hoever it cant be too thick or else the alternator +ve will short out on the rad core (no thanks)
    alternatively i could go with an uprated TT radiator from mishi or ebay, and then offset it slightly in the engine bay (this would allow a 55mm core)
    Car currently doesn't get hot unless you hammer on it though (after having a few overheating issues due to a dodgy cap)

    Next post will be about header design and fabrication but maybe not now.
  7. accident94

    accident94 New Member

    Front sump, yeah. the engine is almost hard up agains the firewall. have a look at the sump designs im my last post.
    clearences are tight (5-10mm) but im happy with that.

    the front sump shortens the oil pickup, reducing the amount of head the oil pump has to draw and in my mind, reducing oil starvation issues. (stock sump is front)

    the front sump also leaves a lot of space where the VH starter motor was, and under the car behind the crossmember

    this is where the headers will go. i've built a set already, but made a few critical mistakes. they'd work but would be leaky and are hard to work with, so im gonna make another set.

    stay tuned for my next post for some detail. i've got a bunch of photos and designs and math and other fun things to share but im hungry RN and should really do some study or something. #MechEngLyf
  8. Chrispy

    Chrispy Pretentious Upstart

    Look forward to it...

    I had a accusump on mine - saved it a few times I think. My sump was a lot smaller than yours though.

    And good to see another mech engineer ;)
  9. stumagoo

    stumagoo Active Member

    Awesome read - really like where this is heading
  10. accident94

    accident94 New Member


    i should add that a lot of this has already been done.
    one set of headers has been made but i didnt like them so the engine got installed without them. another set is on the cards.

    First a little theory. For those of you not familiar with the concept, 180 degree headers (or crossplane/crossover headers) are headers that pair cylinders by firing order, not by such trivial concerns as what side of the engine they come out on. you pair exhaust pulses that are 180 degrees apart, and each collector gets evenly timed pulses of exhaust gas. (normally, v8's fire LRLLRLRR, so the left header would for example, get pulses like this : L-LL-L--. 180 degree headers smooth this out so the left collector you will get L-L-R-R- and vice versa.

    on a vh45 the firing order is 1-8-7-3-6-5-4-2
    these are paired as such

    so 1 and 6 are a pair, 7 and 4 are a pair, so on.
    This gives the engine the same exhaust characteristics as a flatplane v8, like those found in ferraris and the like, but without the inherent imbalance of a flatplane crank.
    the green string in this picture is my attempt to visualise all this (as well as get an idea of lengths.


    Ford's famous GT40 le-mans car used this exact same type of exhaust.


    for tuning purposes you effectively have two sets of I4 headers. These can be 4-2-1 (better for low and mid range, which i considered, but due to tuned lengths and piping difficulties, this proved difficult) or 4-1 (better for mid to high end).

    so after some fancy maths (see four stroke performance tuning by a. graham bell) i settled on 40 inch primaries. Yes this is long, but for the RPM range im shooting for it's about right. 40 inches also gives me just enough length to achieve the crossover. i'm also looking at 1.75 inch diameter on the primaries, collecting into a 3 inch short collector. Collector design is a big thing, i know, but after cramming 4 meters of tubing in there, space is at a premium.

    I got header flanges laser cut locally from 10mm mild steel plate. I wanted to use stainless, but i expected to have to remake these and the added cost + need to purge when welding were dealbreakers. Header tubes and mandrel bends were ordered from ECS engines (Some other bends i ordered from playtime auto parts weren't round and were overly thinned. if you build headers, my advice is to avoid them)
    in total what i used was 20x 180 degree 1.75inch bends, 2x 1.75inch 1m straight 2x 4-1 pressed collector, as well as a 02 sensor bungs and a few other bits and peices.

    i set up my chop saw to cut the tubes square, with a jig made from an old paint tin and some scrap sheet. This proved to be a decent way to do this, but every pipe required a bit of cleanup with bench grinder and die grinder. I cant afford a cold saw so i'll live with it.


    At this point i should probably mentoin the big yellow blob thats in these photos.
    i am lazy. i have no interest in taking an engine in and out of a car repteatedly, so i made a crossmember out of expandafoam.
    wrapped the crossmember in glad wrap then sprayed expandafoam. wait for it to set and you have a crude mould.
    more glad wrap and more expandafoam and you have a foam crossmember This was accurate enough to get everything pretty much bang on, save for the steering column which got in the way C O N S T A N T L Y.

    SO. the headers.
    i do have some progress shots but really theres not a lot to see. I routed all the headers first with string, then with welding filler rod, then with 40mm flex tube, that i slid all the peices over for assembly to give an accurate final length. (the grey tubing in the next photo)

    after a lot of screwing around i got everything roughed up


    and started welded them, before realising i couldn't get the headers off wonce they were welded.
    so i had to source some 1.75inch v band clamps all the way form china land (coulnt find them anywhere else)
    then finished welding the two halves.
    Stupidly, i put the v-bands in places where the two halves are almost still captive, so they're a pain to get off. plus they warped slightly during welding.


    i had planned to squash the port ends of the primaries to size using a custom CNC die. that didnt work so they got the hammer treatment.


    after editing several times to clear the steering column, the headers were finish welded (albiet in a bit of a rush. then painted them with VHT header paint and wrapped them with fibreglass.

    can't find any pictures of the finished product (my PC filing system is a mess) but i'll find some and post them when i do.

    so, any questions?
    happy to provide all relevant info, and designs. would also be willing to throw together ITB kits depending on interest. can theoretically adjust the design to any head/engine - even the stock vg30 (although i'd need measurements)
  11. Always wanted an itb z. Mate your build is the bees knee's, will be watching this with great interest, good luck.
  12. Mitch

    Mitch Has one gear: GO

    4 stroke performance tuning is a great read.
    I also have his other book- forced induction performance tuning.
  13. stumagoo

    stumagoo Active Member

    have to say still enjoying seeing the work going into this build....... its just awesome
  14. induetime

    induetime Induetime

    Nice build thread!
  15. Sketchy

    Sketchy Sick to the power of rad

    Absolutely loving the exhaust and general fab work. Has given me a bunch of ideas for future projects.
  16. noel0leon

    noel0leon Member

    Wow, great work man.
  17. accident94

    accident94 New Member

    Im finally back home for 4 months after another semester in tasmania, so expect to see some more updates soon

    For now, i'll catch you up. The car is running, but ive been chasing overheating issues ever since its been running. Ordered a 3 core alloy radiator to suit a TT, but of course it didn't fit without moving the alternator (again) and mounting the radiator offset to the drivers side.
    Re-made all the alternator bracketing which is now as backwards as it can possibly be (bit it works), as well as welding on new rad mounts (decided against the tek screw method) and all the smaller things like mounts for the overflow bottle etc. (rare pic of me all dressed up with nothing to weld)
    And of course, it still gets hot. Tested the thermostat, which opens fine. finally had a look at water pump part numbers. The one i got on my replacement 94 vh45 leaked, so i swapped the one from the busted '91 on. Turns out they're slightly different
    Ordered a new one, should be here in a few days, so hopefully this fixes the overheating problem and i cen get on to doing exciting modifications.

    In that vein, i got on the lathe and made the spacers for the throttle bodies, and sourced 725cc bosch injectors and fuel rail extrusion. The extrusion is getting machined at the moment, but i have a couple of daydream pics of the throttle bodies in their unnatural habitat. (ft. a good mate of mine who helped a lot over the past few weeks)
    Also, after building a coal furnace, a gas furnace, and ordering the parts for an electric furnace, ive decided to try and 3d print the final part using polycarbonate, instead of using PLA and the lost plastic casting method as previously planned. I bought a 3d printer recently, and it has been getting the same homebrew mod treatment as the Z gets, so should soon be up to the (challenging) task of 3d printing in PC.

    Anyway, thats it for now.
    i'll post more updates as they come (hopefully)
    Zeo likes this.
  18. Sketchy

    Sketchy Sick to the power of rad

    Slightly off topic, how much critical information would you need to design a crossplane manifold for some old mercedes v8's?

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