Preparing For Honda K24a3/AST5 6spd Conversion

Discussion in 'Workshop Forum' started by lookforjoe, Aug 31, 2018.

  1. lookforjoe

    lookforjoe True Classic

    EDIT (Aug 2019): K24 Install Thread Here

    Going to use this to keep (myself organized) track of the parts and process for this build. I will edit the list as I proceed. Plan is to do this next spring.

    So far, I have on order:

    1) '05 Acura TSX JDM K24A3 (190bhp) / AST5 6spd (no LSD) with harness, ECU# 37820-RBB-E05. Claimed 65K miles.
    Engine Code 6RBB-QA000 592 / K24A3-401753(x possible missing digit)

    Engine Spec:
    Trans Spec:

    NOTE: Use of the later transmission requires replacing the right inner axle, shifter gate and shift cable bracket with the earlier (RSX) style, if you are using the MWB axles and shift kit. Also, the MWB transmission mount brackets don't work as the mount points don't exist. Additional brackets/attachments have to be fabricated in order to attach them.

    Rear adaptor bracket


    2) RSX Type S K20A2 oil pump with baffle, oil pan & hardware (recommended to clear MWB kit & gain ground clearance, and oil pump design has higher volume/less parasitic drag)

    Other stuff needed:

    ECU will get a modified K-Tuner User Board installed (, authorized dealer) ✓

    Accord ECU (drive by cable) 37820-RAD-A04

    02/20/20 EDIT: Accord ECU has no MIL cluster feed (E31), will be looking at using '05 RSX ECU 03782-PND-063

    K20 Swap Kit from MWB ✓
    Rear adaptor bracket for AST5 transmission
    Forward adaptor for AST5

    '07 TSX higher lift (.9mm) Intake Cam (used) ✓
    Modified VTEC Gear (30º vs. 25º advance) EDIT: Installed RSX 50º gear, limited to 40º
    Oil pressure sender adaptor
    Red powder coated valve cover
    Oil Filter 15400-PLM-A01 ✓
    Spark Plug set - NGK 6994
    Used RSX Oil Pump, Baffle, hardware & Oil Pan ✓
    Oil pump chain 13441-PCX-004
    guide 13460-PNC-004
    Front crank seal, cover oring
    Rear crank seal BECK/ARNLEY 0523424 ✓
    Serp. Idler Pulley/Bearing 31180-PNA-003
    Blox oil baffle kit
    Crank pulley tool
    Breather housing oring 19322-PCX-003
    Oil Cooler base oring 91316-PE7-730

    Nippon Racing RL5 (11.13:1) 87.5 pistons
    Rebore & hone bores to 87.5 ✓
    King Std. Rod Bearings
    DNJ K24A head gasket set
    K24a Timing chain kit
    VDO 100psi Oil Pressure Sender, 1/8npt

    Throttle Cable - Venhill
    Throttle body extension housing x (Modified intake plenum instead) ✓
    Modified RBB Intake/Plenum
    Throttle body (to replace drive-by-wire setup?) K-Tuned 80mm
    IACV - 16022-PRB-A01, pigtail
    TPS - RAA-A02 pigtail
    '05 Accord ECU 37820-RAD-A04 ✓
    Bosch O2 sensor 15482
    Billet fuel rail (black) x Use stock rail (for AC Comp clearance)
    Fuel Pressure Gauge Adaptor
    410cc Denso Injectors
    Reference list of applicable engine sensors

    19410-RBC-000 (BA 131-2373) Water Pump (fits K24A3)
    GMB K20A3 Water Pump (w/oil cooler) (returned) x
    Water Passage Outlet gasket 18714-RAA-A01
    Oil Cooler hoses: 19422-PRB-A00 19423-PRB-A00
    Oil cooler hose fitting o rings (2) 91311-PRB-A00
    Coolant expansion tank Dorman 603-027
    T/stat Volvo C30/RNC 31319606
    Volvo 84ºC T/stat ✓
    Note: 1 3/8" Fiat tubes
    1 3/8" Hose Couplers (maybe)
    1 1/4" 45º silicone elbow hose, 4" legs ✓
    1 3/8" - 1" silicone reducer elbow hose (instead of above) ?
    1 3/8" - 1 1/4" 45º silicone reducer elbow hose, 4" legs ✓
    Intake manifold adaptor housing (modified) KTD-K24-IMA ✓
    T/stat Extension Housing (custom) + gasket ✓
    Modified Rad & heater feed housing

    3/8" NPT aluminum bungs
    Recirc hose Gates 19498

    Exhaust Manifold Gasket 18115-PNA-004 ✓
    PRB/K20 Intake Manifold Gasket 17055-PNA-004 ✓
    RBB Intake breather system gasket
    RBB Intake Runner Gasket Mahle MS19475 ✓

    Valve cover gasket kit 12341RTA000
    HondaBond Hi-Temp Silicone
    Permatex Ultra-Grey
    LukOil Assembly Lube
    Honda Ultra Flange Sealant 08718-0009

    Shorty Header x
    Custom Header - 2" SS tube, 2" SS 90º Mandrel bends ✓
    Cone Engineering Collector/merge collector
    SS Muffler 2.5" I/O (Magnaflow 11236) ✓
    SS Cat 2.5" I/O
    2.5" SS mandrel bend U- Y pipes ✓
    2.5" SS rigid liner flex liner ✓
    3" - 2.5" SS reducer ✓
    Saddle O2 Bung (x2) ✓

    AC Mods:
    Compressor mount
    Alternate AC setup
    Compressor Hoses, #6, #8, #10
    Orifice Tube/expansion valve bypass (bore out expansion valve)
    Daytona Serpentine 6PK1650
    Additional Idler 31180-PNA-003
    Cone seat 31185-PNA-003
    many #8, #10, #12 hose beadlock fittings
    AC Heater Box

    Stiffer (progressive rate) rear springs for my coilovers: QA1 12HT175/350
    Honda CV's 44310-Ta0-A60 & 44310-Sda-A60
    Right inner axle assy. 44500-SCV-A00 (different length than K24 application)✓
    New boot kits & outer CV's
    Clutch & Flywheel Kit ✓
    Right Axle Seal 91206-PHR-003 ✓
    Honda Urea grease (08798-9002) ✓

    Clutch Slave LUK LSC452
    Left axle seal (SKF 15888) ✓
    RSX Shifter assy (2002-2004 Acura RSX) ✓
    Drilling& Tapping for RSX shift module
    RSX shifter cable bracket (24601-PNS-000) ✓
    New Mount for RSX shifter Bracket
    Honda MT Oil # 087989031 2qts.✓
    MFactory LSDInstall
    Torco A200022CE -MTF 2qts ✓

    Heat sheath for shifter cables (1" ID?) ✓

    Modified clutch pedal pivot (Rodgers) (remove from parts car)
    Modified throttle pedal pivot (Rodgers)
    Modified return spring setup
    Hydraulic slave cylinder hose adaptors
    Brake pedal box mods for Dual Master

    Engine offset/positioning
    Engine Install

    Sheet metal supplies for frame/firewall alterations
    (18ga.) 0.048" T-304-2B Annealed Stainless Sheet 12" x36" x3 (for starters) ✓
    .030" SS sheet 12x36" x3 ✓
    .048" 13x22" for access cover ✓
    .048" 13x31.25 for trunk floor ✓
    Spot Weld Cutter tool
    Cleco 1/8" fasteners
    12' x2", 3'x 1.5" Angle Iron(to make Sheet Metal Brake, in order to make box sections) ✓
    6' x1.25" Square Tube (for cross brace above rear crossmember) ✓
    6' x2" "C" channel (for rear crossmember bracing) ✓
    Firewall Insulation (Dynamat 11905 34"x54", .75") ✓
    1/4" closed cell shielded insulation 1x1.4m ✓
    Much primer & Sunrise Red spray cans
    3M Rocker Schutz 08874
    3M Undercoat 08864
    2" closed cell foam tape to seal apertures ✓
    2x Dynatron seam sealer/caulk
    edge guard for SS panels


    10' 4ga battery cable
    15' 0ga battery cable (taken from Volvo V70)
    Buss bar
    Drivetrain ground strap
    Ground buss
    Alex Tech sheathing, 25' pkg of 1/8", 1/4", 1/2" ✓
    ODBII port
    Marshall Tach & Speedo install

    In place:

    Coilovers (change rear springs - done, OCT '18)
    Front swaybar (Volvo 760)
    Larger brakes (Vick Auto) EDIT: CEIKA brakes
    Modified fuel delivery (Bosch M4.4 FPR with return built in)
    Electronic speedo (need to adjust signal conversion through Speed Healer?)
    Larger all aluminum radiator (custom, HoweRacing)

    (Current) Reference threads:

    Rodger1 (ECU wiring)
    Rodger (Exhaust)
    Fiatmonkey #2
    AC Retrofit post #15
    Compressor mounting and HERE
    LarryC's AC Heater Box

    K20 Swap Australia

    "B" series swap - AutoX1/9

    Clarks' Dash Thread (not K20-related, but need to keep track of it :)

    Resource Forum:
    Last edited: Feb 22, 2020 at 2:31 PM
    PaulD, davejake, Hasbro and 2 others like this.
  2. JimD

    JimD Waiting for Godot... Moderator

    Missouri, USA
    First reply!!! No one can take that away from me!

    I would say "Good luck Hussein!", but in your case, luck has nothing to do with it. Hard work and perseverance. That's the ticket. :)
    lookforjoe and AKimball92 like this.
  3. AKimball92

    AKimball92 True Classic

    An actual BOM is nice to see. I haven't done much research into the K20 swap as its out of my space, budget, and skills at the moment but haven't seen mention elsewhere of a list of items needed to start. Looking forward to following.
    kmead likes this.
  4. kmead

    kmead Over half way.

    I resisted the temptation to be first and clutter up the thread, but there you go Jim, making a mess of things and opening the door to all the rest of us riff raff...
    JimD and lookforjoe like this.
  5. Daniel Forest

    Daniel Forest True Classic

    I'm just disapointed there is no VOLVO parts in there... (yet)
    fiatmonkey, lookforjoe and autox19 like this.
  6. Hey Hussein,

    I'm intrigued as to why you went for the Honda option. In this thread, you seemed to be leaning towards a Fiat DOHC which I'm sure you would have done well with ;).

    I'm assuming that the deciding factor was parts availability in North America. I'd note that the Fiat DOHC was able to achieve 210 BHP in the HF integrale Evo2 variant which won, albeit in a highly modified form, the WRC constructors championships in 1987, 1988, 1989, 1990, 1991 and 1992. I've never seen a Honda do that! Johannes Graversen's X1/9 is probably the ultimate evolution of the SOHC motor as well. That said, I'd admit that a Honda swap would probably be a safer bet in the US.

    Anyway, good luck with it! Looking forward to seeing the progress.

    lookforjoe likes this.
  7. Mechanogeek

    Mechanogeek True Classic

    Jacksonville, FL
  8. lookforjoe

    lookforjoe True Classic

    Hello Dom. Yes, I would have liked to have kept the powertrain Fiat/Lancia. Based on the discussion & info provided, I couldn’t see any practical way to locate parts from overseas without massive potential for error. When it became apparent that Fiat 16V was problematic I lost interest. DOHC 8 valve holds zero interest for me - that seemed to be the easier solution, following Steve’s posts.

    The Honda powertrain is much newer technology, and support for swap related parts is easy to find.
    kmead likes this.
  9. Hasbro

    Hasbro True Classic

    Danielsville, Ga
    Insert popcorn eating smilies here. Would have been nice to have another 2.0 tc build along with mine but I'm thrilled you're doing a K24 build!
  10. Dr.Jeff

    Dr.Jeff True Classic

    Sin City
    I'm sure you considered a complete Volvo swap of some sort? Especially with your knowledge of the brand. I don't know what could be used from Volvo, but that would have been really interesting. Curious what you might have done in that direction? And why you didn't?
  11. kmead

    kmead Over half way.

    Because the only US transverse engine of note was the T5 which is likely a bit wide for an X.

    In Europe I believe they had a 4 cylinder but none here. There always also the preponderance of oh so tragic transmissions ie automatics primarily aside from the early V40/50 and a peppering of C30 manuals.
  12. lookforjoe

    lookforjoe True Classic

    I would have liked to use a Volvo drivetrain. Karl mentioned the T5, which is actually a modular design (like many companies) that was sold in 4, 5 & 6 cyl NA and Turbo configurations here and around the world. The problem in the US is that the 4cyl was only ever mated with an automatic transaxle, and those were only used 2000-mid 2004. I could use the same manual 6 spd transaxle that is in my C30 with one of those 4 cyl, but then the existing 4 cyl EMS won't operate. Since I would have been looking at a complete 4 cyl engine/trans/EMS to drop in (No support for aftermarket tuning with that) there was no way practical to do it. The drivetrain is also heavy & bulky compared to the Honda unit, and of course I'd have to locate a source for hybrid axles, come up with my own subframe design, etc... Beyond all that, I also want to do this in as an expedient a fashion as is possible when the time comes, which the Honda swap with all the support it has provides.
  13. lookforjoe

    lookforjoe True Classic

    What I've been thinking about today (Karl also mentioned this), is either modifying the stock Honda intake manifold or making my own, to reduce the firewall intrusion & funky TB extension housing business. Found this old K20a thread in my search for data on changing runner design / length on these motors. At a glance (looking at Rodger's intake/plenum), it (the K24a3) has much longer runners, which makes sense since it is a (slightly) lower revving motor with more low-mid range torque. I may use a pre-'99 Volvo V70 TB similar to that which I added to the X1/9, as those are throttle cable operated, cheap, and compact in design, and 2.75" ID.

    K24A3 RBB

    K20 (Rodger's) PRB


    Tim's K20 (?):


    The last intake I built was for my old Volvo. That was Turbo-charged. I make the plenum diffuser-style. The shorter ( than stock, 6") runners had zero negative impact on low-mid range torque, on that setup anyway.



    Last edited: Sep 10, 2018
    Hasbro and kmead like this.
  14. Dr.Jeff

    Dr.Jeff True Classic

    Sin City
    Good job on the manifold!
  15. sub-zeroil

    sub-zeroil True Classic

    hollywood fl
    i have hybrid racing fuel rail if you need but its gold !
  16. kmead

    kmead Over half way.

    Nice work.

    In perusing the images of intakes on the web, there are a number of companies I found pretty interesting in terms of their approach. Skunk Racing uses a removable plenum box half which allows one to add air horns into the intake runners. Toyota also took this approach with the Matrix/Corolla intake manifold for the 2ZZ engine, a bit different but similar.

    Skunk manifold, center feed. It looks like the plenum could be flipped top to bottom given that the gasket is symmetrical.
    0E68B415-A58F-41C1-8055-4E4316D930B7.jpeg 7025ECE1-13DF-4757-982E-C434F1F0E5A3.jpeg A2E0FE69-E532-491B-9BB9-FB72ED3A0EC7.jpeg 0528E2B1-F58A-45E2-9D26-FB85E2575B1C.png 135093E2-6332-40C3-A699-FC5CA8198C2C.jpeg

    The Toyota 2ZZ manifold installed in the Pontiac Matrix and Toyota Corolla
    A2F81360-24ED-4BA2-B4DB-AB0B404EA29C.jpeg 7482A882-987D-41D6-A8AC-08FC15722909.jpeg 30659750-33C0-4CD5-AA44-7BADCC2EE7E3.jpeg
  17. kmead

    kmead Over half way.

    A possible approach to the manifold with an upward cant versus downward. The radius into the head is effectively immaterial as the lead in to the valves in basically level with the downward slope to the valves starting beyond where the manifold ends.

    26562FF5-47BE-478A-A5CC-E7B1D10ECF52.jpeg BCA92CE3-666D-4D51-B624-54A6EDE2B671.jpeg 250EBFF8-A0E1-4BA7-B244-5F9AA4C84565.jpeg

    fiatmonkey likes this.
  18. stingray250

    stingray250 True Classic

    From this...


    To this...


    The Saab turbo manifold is half the size of the stock GM composite... All for 34.95 on eBay... Bolts right up to the GM 2.2/2.4.
    I sure love my Ecotec! So many parts that are swappable...
    lookforjoe and kmead like this.
  19. fiatmonkey

    fiatmonkey Tim Hoover

    Redwood City, CA
    Love the idea but clearance maybe? However thinking about it, likely wouldn’t be any higher than the AC compressor or the rotrex supercharger. I was using a 75 engine lid with the red k20+rotrex and I had to raise the hinge side and just used the upper studs (in the lower holes of the hinges). Worked and looked great.
  20. kmead

    kmead Over half way.

    Thanks. I was thinking more of it being a tight winder over the head like the X and its log but you get the idea in any case.
    fiatmonkey likes this.

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