Preparing For Honda K24a3/AST5 6spd Conversion

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

  1. lookforjoe

    lookforjoe True Classic

    Looking at your pics, I assumed you were utilizing the covers for (potential) load transfer, they look great. I didn't catch the addtional plate reinforcements in the firewall work. I'm assuming the vertical plates were added prior to the horizontal sections.

    I'm thinking I'm going to use box section across the top of the rear crossmember. On mine, the existing stock lip/flange that secures the access cover has a decent amount of rust, so I'll just cut that out, add a crossmember & add the lip back on top.

    I'm curious how the right forward corner was dealt with beneath the surface plate, where the original inner vertical panel was removed. Since that area carries the right control arm mount, did you add any additional support or bracing in that 'well'?

    Screen Shot 2019-02-04 at 9.15.13 PM.png

    Initial prep work 09.jpg
  2. darwoodious

    darwoodious Darin Nelson

    Seattle, WA
    I'm guessing you mean the front of the engine bay? Yeah, I know that a large (stock) box section can be strong and when you go smaller as is needed for clearance on the K20 fitment you need to have a stronger box-section. So once the cuts were made, I added a layer on the insides - the more substantial one you saw in my pic which is the forward facing side of the box section. I also added to the backside on the inside. Digging up some photos...

    Before adding anything:

    Next, this is probably the same you saw earlier - the front part welded in but you'll notice I added in a gusset over the suspension/subframe mount here.
    WP_20160528_13_17_46_Pro (2).jpg

    Here's another, better photo of it.
    WP_20160528_13_18_00_Pro (2).jpg

    Not sure if you can see it all that well, but here you can see the inside of the back part of the frame has been "doubled" in a couple of places - both on the long middle run as well as the back part of the passenger side subframe. I put some arrows to assist. The two red arrows show the doubled sections. The green arrow is the added vertical gusset:
    WP_20160528_13_18_15_Pro (2).jpg

    All I did for that is to use two plates and weld where the original vertical section intersected the cut. You can kind of see it here if you reference the before photos.

    I dunno, but I'm pretty sure this is WAY stronger than stock. I did of course add a few pounds of metal to the car over stock, but not too much (I hope).

    That's the fun part of this project - you get the MWB K20 conversion instructions and it pretty much gives you course map of what to do, but the specifics are up to the builder. Until you get cutting and welding, you're not really sure. Once you're in there and give it a few minutes of thought, it becomes pretty clear on how to match or even improve the strength of the chassis. I know lots of folks here thinks it's crazy but honestly I really can't imagine any scenario where a well done K20 conversion isn't stronger than stock. You do of course add a bit of weight, but hey - you're getting a bunch more power right?

    Have fun with your build Hussein!

    Attached Files:

    lookforjoe and nichol01 like this.
  3. lookforjoe

    lookforjoe True Classic

    Thank you for the detailed photos & suggestions, that is most helpful. Making the crossmember double wall like that seems to be the most practical approach, I'll follow your example on that, I think. I would expect the weight differential is not that great, given how much is also removed. Not going to matter much with the over 100% power gains :D

    EDIT: what weight magnets did you use for all this? Are they the 10 or 25lb version?



    One thing I haven't been really able to gauge accurately from yours, Rodgers or Tim's pics is how much the right frame rail is relieved. Also if you can give the measurements you settled on for cut height of the crossmember I would be most appreciative :


    Attached Files:

    Last edited: Feb 6, 2019
  4. darwoodious

    darwoodious Darin Nelson

    Seattle, WA
    Sure - no problem. I couldn't easily get to the front to measure your #2 in the photo, but took a measurement at the right side of the cut from the top of the existing box section to where the cut ends. Please do note though that I did what Rodger did - I wanted the access port a bit lower in the car so I located that lower. You can't really cut until you get the MWB kit (unless you make your own which is totally doable, but hey - you're already gonna pay for it!)

    Hope these help. Love seeing your progress. Wish I was making more progress myself!




    #2 substitute

    Bonus images:
    IMG_2837.jpg IMG_2841.jpg
    lookforjoe likes this.
  5. lookforjoe

    lookforjoe True Classic

    Thank you for taking the time to document for me. The orientation of some of them threw me off for a couple minutes :D

    Those will help me gauge best place to make initial cuts. I'm planning on doing the same lowered access entry as you & Rodger. One thing I've been wondering about it is cutting & folding existing metal in some of those areas vs. removing old entirely & having to seam weld so many intersections. Maybe it's just not practical. I'm going to practise cutting on my parts car first anyway.

    Looking through some of my old pics I have added an annoying layer of extra work - I dynomatted the entire exhaust bay, including the crossmember. That's gonna be a fun removal job :(

    Last edited: Mar 10, 2019
  6. lookforjoe

    lookforjoe True Classic

    Thinking about the cuts in the left frame rail. This is the one that honestly gives me the willies when I look at the cuts. Sketches based on Rodger's and Tim's pics.


    Tim's is only notched at the back


    Pic from Rodgers with trans in place. I'll reduce the depth of the cut, and push out the outer skin as he suggested


    From earlier reference of Rodger's, with lesser cut, looks about 1/2 rail depth. I'm going to cut that raised boss off the trans if it means the cut can be reduced in severity.

    Rodger likes this.
  7. darwoodious

    darwoodious Darin Nelson

    Seattle, WA
    Before I really got into it I thought that I would leave about 1/2" as well. I was wrong... Once I put the drive-train in I found I needed it a bit wider, thus all my previously posted photos showing that the wall cuts basically to the edge of the wheel well inner.

    I don't know why there is such consternation about doing that though. The box section is good for "twist". Your subframe will pick up a lot of that. Plus, the twist is the box area of the engine bay. Probably more important is to trasmit the vertical load from the passenger side of the chassis (from the top of the left-rear strut tower to the rear firewall, center tunnel and outer channel.

    Just my 2 cents.
  8. lookforjoe

    lookforjoe True Classic

    Thanks for the input, Darin.

    I guess it's just the visual - with the rail cut to the point where there is only that thin vertical/diagonal connection at the forward end, it just looks like it has nothing but the wheel arch holding it together. I'm sure the new subframe helps spread the load, it still looks 'wrong' :D

    I was referring to the vertical depth of the rail, not the lateral width, which is what I think you are referring to

    "Once I put the drive-train in I found I needed it a bit wider, thus all my previously posted photos showing that the wall cuts basically to the edge of the wheel well inner"

    Maybe add a box section to the forward end

    Last edited: Feb 7, 2019
  9. Rodger

    Rodger True Classic

    Olympia, WA
    My two cents. To me, the whole engine compartment is one big rigid box, with considerable stiffness added by the front and rear firewalls, inner and outer fenders, as well as the front to rear and side to side frame rails. Cutting a large section of the left side rail to clear the transmission will probably reduce the stiffness slightly, but I doubt that it would be of any significance from a performance point of view as it does get boxed back in, plus there is the addition of the subframe. Acceleration and braking loads, as well the twist from cornering, are probably well resisted by the whole box structure.

    I think where cutting out that section could be an issue is in the case of a rear end collision on the left rear quarter that would transmit the force forward along that whole frame rail. I could see the rail bending in the cut area since it is arched and the vertical cross section is much smaller than anywhere else along it. How much of an impact would it take to do that? I have no idea and hope I will never find out. I'm sure that would total the car anyway. Maybe a project for Carl to try with one of his wrecks. Cut out that section and let the car roll backwards into his new utility pole to see what happens. :rolleyes:
    darwoodious and lookforjoe like this.
  10. lookforjoe

    lookforjoe True Classic

    Forgot to ask - what's the pipe for? Drainage?

    EDIT: what's the hold up on yours, Darin? Just life getting in the way?


    My MWB kit is scheduled to arrive tomorrow :)
    Last edited: Feb 8, 2019
  11. darwoodious

    darwoodious Darin Nelson

    Seattle, WA
    Yeah... life and I wanna do all the bodywork (welding, fender folding, etc) myself before paint. That, a full time job, family... I get to it frequently enough but I'm super slow. It's amazing to see the crazy stuff you and others do in what seems record time to me.

    No worries - it'll be in for paint this spring. After that it's all uphill... a very long uphill but thats cool.

    That tube is welded in the forward outer sides under the side cool air vents in the engine bay on both sides. It will carry the fuel lines and the hard brake lines. Fuel will run from the tank across behind the spare tire area (fuel pump location) up thru that tube, into a fuel filter in that unused area under the pre-80 side cover and into the fuel rail. End of the fuel rail has the regulator then back to the other (driver's) side and back to return. I did that after seeing the tight fit on photos for stock brake lines as well as fuel lines. It was easy: a hole saw and an 1.5" tube.

    Back to your build - now that your MWB kit will arrive I'm sure you'll be kicking @$$ on your build and finish before I'm done. All will be very clear now that you have the kit. Have fun and enjoy it.

    PS: I also have a new distraction in the form of a 2018 Shelby GT350 which takes some of my garage time - when it's not snowing and crap weather.
    lookforjoe likes this.
  12. Mechanogeek

    Mechanogeek True Classic

    Jacksonville, FL
    Double thumbs up on that sentiment!
  13. lookforjoe

    lookforjoe True Classic

    My kids are grown & long gone, so it's just my wife & I. As a high school teacher, I have hours of daylight work time after school, when the weather gets a little better :)

    The tube for line routing makes sense. I'll have to look at that. You could consider a "returnless" setup (if you haven't already invested in what you describe), where the return comes off a remote FPR, closer to the tank. Greatly simplifies the quantity of fuel lines & safer, IMO.

    My plan is to do the C30 AWD conversion before I start cutting up the X1/9, or I won't have a car to drive. The AWD donor car still hasn't arrived, and may not be here until end of Feb. So, I'm going to run out of a decent window to get that done before spring gets well underway, which will push the K24 swap back :(
  14. autox19

    autox19 True Classic

    East Lansing, Mi
    are you going to have a place online we could follow that AWD build? I love following your projects.

  15. lookforjoe

    lookforjoe True Classic

    Thank you

    I added a thread on here, I value the input of members here. This one is pretty much cut & dry parts swap though, besides some electronics concerns with fuel gauge and Haldex controller
    dllubin likes this.
  16. Hussein:

    I'm hoping your great example will help motivate me to get started on my T5R engine rebuild.

  17. lookforjoe

    lookforjoe True Classic

    Doing anything fancy?





    Or just stock rebuild? :D
    stingray250 likes this.
  18. Well, I have not quite decided yet. It sounds like I spun the #5 con rod bearing, and the motor is right around 200K so I'm sure it could use a general overhaul at minimum. In current form, I'd say it is running somewhere in the 280 -290 hp range. Problem is that there are turns where it is tough to use all that power with that chassis. It was much worse before I lowered it ~1.5" but even now in a tight reverse banked turn I can still get enough inner wheel lift to loose traction. I'm currently running 215/45-17 Pilot Super Sports which are great as long as they are on the pavement and could probably go up in tire width a little swapping out the fender liners but in the end it is a whole lot of work to get anything wider in there. If I were doing it today, I'd definitely take the AWD route like you are. Back then, that choice wasn't available, and it was about the fastest 4 door sedan you could buy in 1995.
    lookforjoe likes this.
  19. lookforjoe

    lookforjoe True Classic

    Kit arrived a couple days ago. Very nice construction. The only niggling thing I can say is that the shifter detent lever has slop in it, due to play between the bolt used as the shaft, and the lever tube. I took a piece of a guide bushing & bored it out to be a snug fit on the bolt, and a slide fit in the lever pivot. Now, there is only the slightest play, which is between the helm & the slide rod on the main shaft.


    Worked on the cable attachments. Cut the barrels off the provided heims & welded them to the Acura ends. Finished the sleeves that allow the cables to fit in the stock bracket.




    Test fit the one engine support bracket that goes under the waterpump housing area. I thought I might have set the heater hose attachment to far back, and indeed I had. I'll have to revisit that.

    Last edited: Feb 12, 2019
  20. darwoodious

    darwoodious Darin Nelson

    Seattle, WA
    wait... how did you weld this up without melting the rubber? did you pop out the rubber bushings first?


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