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170 Posts
Discussion Starter · #1 · (Edited)
I'll keep this list at the beginning of parts used up to date so theres no more question of what is really needed with the z3, sometimes referred to as the most difficult of the K20 swaps because of the DBW throttle body, CannBus system, and other things that well get into during the thread.

Required (Or something similar of a different brand)
K20z3 out of a 06 Civic SI
K20z3 Trans out of an 09 Civic SI
K20z3 Starter
K20a2 Throttle Body with sensors
K20a2 Engine Harness and Charge Harness
K20a2 Intermediate Shaft and mounting bolts
K20a2 Alternator
OBX Throttle Body Adapter
Chase Bays Clutch Line
Hybrid Racing Swap Harness
Hybrid Racing Tucked Fuel Line Kit
Hybrid Racing Fuel Rail
Hybrid Racing K20z3 Swap Shifter
Hybrid Racing K20z3 Swap Radiator Hoses
Hytech Replica Stainless K-swap Header
Aeromotive A1000-6 Fuel Pressure Regulator
Aeromotive Fuel Pressure Gauge
Aeromotive 15606 ORB-6 to -6AN Adapter x3
Vibrant Intake Filter
Vibrant 90 degre Intake Tube
Vibrant Stainless Steel Worm Clamps
Vibrant 2.5" to 3" Reducer Coupler

Optional Stuff:
AP1 Cluster with Pigtails
Glowshift DC2 twin gauge cluster
Hybrid Racing K20z3 Oil Cooler Hoses
Hybrid Racing 06 Civic SI Shifter Bushings
Autometer Sport-Comp II Oil Pressure Gauge
Autometer Sport-Comp II Water Temp Gauge
Karcepts Cruise Control Delete Kit with GSR Cable
91-95 MR2 Electric Power Steering Pump
Perma-Cool Power Steering Cooler Kit
Tyco V23232-A0001-X003 12V Diode Surpressed Relay
Rebuild trans with newest Honda gear set to prevent 2/3 synchro going, new 2/3 synchro, new 3/4 synchro, new axel seals, and new TOB fork seal
OEM Honda Water Pump: 19200-RBC-013
OEM Honda Thermostat: 19301-RAF-004
OEM Honda Timing Chain: 14401-PNA-004
OEM Honda Tensioner: 14510-PRB-A01
OEM Honda Head Gasket: 12251-RBC-004
OEM Honda Spool Valve Assembly: 15810-PRB-A03
OEM Acura RDX Injectors/Clips:
ACL Race Main/Rod/Thrust Bearings
3/8ths Vac Plug for Idle Air Assist Bypass
3/8ths NPT Plug for Idle Air Assist Bypass
Walbro 255 In Tank Fuel Pump
Walbro Fuel Pump Install Kit
DEI Reflect-A-GOLD Tape
Exhaust Manifold gasket
Front Main Seal
Rear Main Seal Kit
Accessory Belt Auto Tensioner
Fuel Injector O-Ring Set x 3 for an extra pair
Valve Cover Gasket Set
Valve Stem Seal Kit
Oil Pan Gasket
AEM Power Alternator Pulley

Wire Harness/Sensor Layout/Sensor Pinnouts - Page 1
Fuel - Page 1
AP1 Cluster - Page 1
Water - Page 1
VSS Wiring - Page 2
Harness De-Pinning - Page 2
Radiator Cooling Fan Wiring (as per FlackoNAEG's request) - Page 3
Inector and Injector Clip Differences - Page 4

I got the K20z3 for a rediculously good price from a Honda dealership that pulled it due to a bad water pump that potentially could have blown the headgasket. Since these are usually things I look at and replace during my swaps, no problem.

I decided to clean it up a little bit just so it wasn't so dirty when I was trying to see what I had to work with:

The K20z3 trans I got from another dealership that pulled it due to the 2/3 syncro being bad. As anyone knows this is very common on these transmissions. Again, I always have my transmission rebuilt before swaps, so no biggie. I actually just got an update from the place I take all my transmissions to (Probuilt Transmission in Bulter PA) that they were going to be throwing in the revised Honda gearing and syncro that was released to address this issue. It'll set me back $795 bucks to rebuild it, but the way I see that is I now have under a grand in a completely rebuilt and known good z3 transmission. Well worth it to me.

Now that my basis was down it was time to start getting the swap materials together.

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170 Posts
Discussion Starter · #2 ·
First was the K20a2 Throttle Body. The K20z3 comes equipped with a Drive By Wire Throttle Body from the factory. The easiest way to make the conversion to cable driven like our cars come with is by swapping to the a2 cable driven throttle body.

Next is the K20a2 engine harness and charge harness. This is for multiple reasons as far as I can tell. The throttle body swap to remove the DBW, power steering pump, as well as little things such as ECU location are small reasons for the need for this harness. Theres more reasoning to it, but just know that you NEED the a2 harness for this swap.

K20 belt driven power steering pump. The K20z3 powered Civic SI's used electronic power steering pumps. Again the easiest way around this is simply to install a K20 belt driven power steering pump. The idler pulley on the K20z3 unbolts and the K20 belt driven power steering pump bolts directly on to the same bolt locations, even using the same bolts. Therefore this is a true bolt on swap for power steering.

Any K20 intermediate shaft can be used on the swap.

The interior swap harness is required for integration with the chasis harness (gauge cluster, OBDII port, an ECU plug, etc.

I also chose to go with an AP1 cluster. The K20z3 uses a magnetic Vehicle Speed Sensor. S2000's use the same type of VSS. Therefore, I could have either spent a bunch of money on converters to switch to the mechanical VSS signal the DC cluster takes in, or I could spend a couple extra bucks and put in an AP1 cluster and not require any type of converter. I'm a fan of clean installs and keeping it simple, so I went with the AP1 cluster.

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Discussion Starter · #3 ·
Picked up a PRB-A06 ECU today. According to Hondatas website, the following ECU must be used for them to be able to install K-Pro on it:

PRB A01 - PRB A12 & 305.

Can be found in:

02-04 RSX Type S vehicles
MUST BE MANUAL to use KPro (NOTE: All PRB ECU's are manual. Automatic ECU's have 2 extra plugs in the middle of the ECU. So I'm not sure why Hondata has this on their site...but just figured I'd add it onto my post of why I'm buying the things I'm buying.)

Also as an answer to a question I had and no one on the swap forums really came out and answered is can you use the factory K20z3 ecu? I was looking for a cheaper way out than full blown KPro and questioned if I could use Hondatas Flashpro for civic SI on the factory ECU. I went to Jeff Evans (who inevitably will be tuning it) for the answer. He explained that due to the difference in drive by wire throttle body and the much larger issue that the newer ECU's (including 06 and up SI's) incorporate a CAN bus system present in the chassis. So rather than swapping over basically the whole CAN system somehow...much easier to just get the 02-04 A2 ecu.

I also picked up my tranmission from being rebuilt. Ended up being about $820 after tax and all was said and done. They installed the upgraded 2/3 synchro and gear set to the current updated Honda set that they are putting in at dealerships now to solve the 3 popping out of gear and the just bad syncro design that orignally came in the transmission. They also cleaned her all up, re-sealed everything and even got me a new shift fork booty!

This saturday I'm busy hopefully finishing up the motor work on my 240 but I plan on taking the motor up to get checked out and re-freshed next Saturday.

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170 Posts
Discussion Starter · #4 ·
Alright got to this stuff over the weekend but just getting time to put it up now.

First off was getting launching some un needed emissions BS. The "Install Pipe" with purge control solenoid was yanked off to give it a nice clean look. Purpose of this thing is to prevent unused gas vapors from escaping to the atmosphere when the car is turned off. Its usually linked to a charcol canister. Thus making it optional. haha I

I'm not quite sure why some of these are coming out rotated...they're the right way on my photobucket page so if you need to see them correctly just check them out on my photobucket.

Location on motor:

Whole contraption removed:

I also freshened up the trans cosmetically a little. Don't want to have an ugly K swap! I always keep it simple and do aluminum finish on all of my blocks. Though black and other dark colors look good on some motors, it makes it very difficult to track oil leaks when they occur. So if this is your first rebuild make sure you keep the block and head a nice bright color for contrast with oil.


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Discussion Starter · #5 · (Edited)
Wire Harness/Sensor Layout/Sensor Pinnouts

I just decided to dedicate a section of this thread to whats needing to be done with the wiring. My goal is to update this post through the build so anyone looking at doing this swap can refer to this one post for every bit of the wiring that needs to be altered:

First there is a Service Loop in a white wrap on the Passanger side of the motor usually zip tied to the harness just above the VTEC solenoid. This contains the three wires going to the first Ignition Coil. Feel free to tuck these, or as I did just double them back over themselves inside your new harness to hide them.

Secondly there is a Junction Connector Housing on the Driver Side above the transmission.

This is a black plastic piece with the following wires going into it:
(7) Yellow/Black - 12V Ignition from ECU
(4) Black/White - Into Swap Harness, haven't gotten that far yet
(6) Black/Yellow - 12V Ignition from Swap Harness
(6) Brown/Yellow - Logic Ground from ECU
When you take the black housing off you'll find these wires are just all jumpered together inside the housing.

There is usually 1 or 2 coming from the ECU/Swap Harness and then those are sent out to all the sensors for powers and grounds through this housing. I simply cut off this connector and joined all of the Yellow/Blacks together, all of the Black/Whites together, All of the Black/Yellows together, and all of the Brown/Yellows together. This will eliminate this large piece from your harness.

The Oil Pressure Sensor plugs are different between the motors. Requiring you to either A: do an aftermarket gauge if you plan on doing a built motor...probably recommended. Or B: I'm doing nothing special with mine, so I'm good with the normal high/low oil pressure sensor. Therefore I plan on just switching my plug out from the K20z3 harness onto the K20a2 harness so my factory K20z3 pressure sensor will work with my K20a2 harness.

K20a2 Harness Oil Pressure Sensor Connector:

K20z3 Harness Oil Pressure Sensor Connector:

K20z3 Transmission Sensor/Plug Locations and Pinnouts:

K20a2 Throttle Body Sensor/Plug Locations and Pinnouts:

K20z3 Cam Position Sensor, Top Dead Center Sensor, and Engine Coolant Temperature Sensor Locations and Pinnouts:

K20z3 Coil Pack and Injector Locations and Pinnouts:

K20z3 VTEC Oil Pressure Switch, VTEC Solenoid Valve, and Oil Pressure Sensor Locations and Pinnouts:

K20z3 VTEC Oil Control Valve and Crank Sensor Locations and Pinnouts:

K20z3 Knock Sensor Location (I dont have one yet, but it goes here). NOTE:We will need to use a K20a2 Knock Sensor for our swap.:

After taking the short cut and just talking to Jeff at Evan's tuning who has tuned many of my cars in the past and will be tuning this one as well, he said that the only sensors we will be eliminating as far as Kpro is concerned is the Secondary O2 sensor, Purge Solenoid, and EVAP sensor. Remember this is if you are using KPro. If you are using a type R ecu or some other with an immobilizer bypass deletion of these sensors may throw codes.

The Purge Solenoid has a Yellow/Blue wire going to ECU Pin "B21". I de-pinned this from my plug on mine. The other Black/Yellow wire on the Purge Solenoid goes to the Junction Connector mentioned above. So pull both wires out of the harness.

Intake Air Temperature Sensor will be mounted in whatever intake you decide to go with so it is not in any of my pictures. Be sure to remember to keep its harness around though. Just because its not pictured doesn't mean you can eliminate it.

Below is the list of wiring needed at the ECU. Anything else can be removed if its not listed on this spreadsheet. Should help you remove anything not in the harness. NOTE: this is for people running K-Pro. Not sure what would happen with a factory ECU.

I have this in a full PDF file too so its not multiple pictures if anyone would want to have it e-mailed to them let me know.

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Discussion Starter · #6 ·
I also pieced together a home made Idle Air Assist bypass today. Some of the major companies out there sell these for 20 to 30 bucks, but I've included pieces needed to bypass it for less than $2.

This bypass is REQUIRED if running some aftermarket injectors. The factory K series injectors have two O rings around the tip of the injector to allow this to work correctly. If your aftermarket injectors do not have two O rings on the injector nozzel side you must do this or your car will run not so nice.

This part from the factory allows for a quicker warm up when the car is sitting at idle. When the engine coolant temp is below 147 degrees, the valve is open. This allows additional air to come from the intake manifold directly into each injector port. This in turn artificially leans out your fuel mixture allowing the motor to heat up to operating temperature quicker.

Whats needed:
3/8th's vac nipple
24 mil socket/wrench
3/8ths NPT plug (from plumbing section at Lowes/Home Depot/etc)

I found it easier (since I'm not using it) to just give the sensor to little love taps with a hammer since I don't have a 24mm box end wrench handy. I then was able to easily slide a 24mm deep well socket over the remains of the sensor and easily unscrew it out of the manifold. Add some teflon tape to the threads of your NPT plug from you plumbing store, especially recommended if youre doing boost, and screw that bad boy in.

Next throw your 3/8ths vac nipple from advance/autozone/where ever on the center port of the RBC manifold and throw a zip tie on it. No need for a hose clamp here. You can use one if you want but I've had plenty of boosted cars and zip ties do the job just fine and look a little cleaner in this location to me.

Throw a little paint over the plug and enjoy!

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Discussion Starter · #7 ·
Mini update here...almost more of a product review instead. Got in my OBX throttle body spacer and got it all installed.

Reasonings why I went with this one? Its the cheapest AND it comes with both gaskets needed. No other adapter that I found came with the gaskets for the price range.

This is needed to adapt the cable driven K20a2/z1/type r throttle bodies onto the RBC manifold. Make sure you go with the right one. Different manifold/throttle body combinations require different adapters, so make sure you take your time and get the right one.

comes with needed gaskets
2 extra 1/8th inch NPT vac ports right on the front of it
claims to add horsepower with its Vortex effect
overall looks pretty good.
Good throttle body alignment

one of the bolts had a sign of rust on it right out of the package. I was switching these bolts to stainless hardware anyways.
No directions
Bolt holes weren't threaded for the throttle body. Which is why the no directions thing mattered.

Thing came well packaged and in a timely manner off of ebay of course. I cracket it open and something just wasn't making sense just looking at the piece. There were no threads for the bolts that hold the throttle body to the adapter. I thought something had to be wrong so I did a little research and found that this actually seems pretty common with these. I'm not sure why, but the OBX adapters have said to have come with no threads in them before. No biggy. I figured I could break out the ol' tap and die set to save myself 20-40 bucks.

You have to tap out the holes circled in red. 8mm x 1.25 is the tap needed. This is the thread that the bolts supplied are as well, so you can use them if you tap it out with this size.

Other than that it was pretty flawless and straight forward. Couldn't really ask for much more from a 60 dollar part. As you can see the throttle body alignment was dead on and it will most certainly get the job done. I won't be using the 1/8th inch NPT fittings since I'll be running NA, but thoughtful OBX included two nice plugs for the holes.


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Discussion Starter · #8 · (Edited)

So here we go for the fuel systems needs for a Kswap:
Need a regulator to retrofit the returnless K series to the fuel return system in the DC. More on this later.
Fuel pressure sensor which should be a no brainer when running any after market regulator
Fuel Rail
Fuel Lines - K series use returnless fuel systems. In returnless systems the fuel pressure is regulated electronically by the ECU depending on signals from a fuel pressure sensor in conjunction with RPM, O2 sensors, etc.
The DC uses a fuel return system. The good ol type of mechanical regulation. The fuel pressure is regulated by...well the regulator through manifold vac pressure. The higher the pressure, the more fuel the diaphram keeps in the system. THe lower the manifold pressure, the less fuel is in the system. Easy right?

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Discussion Starter · #10 ·
well to be honest I wasn't updating this thread because it didn't look like anyone was reading it. I'll post all the updates over the next few minutes to bring it back up to date. It seems worth my time now that I know someone is actually using it!

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Discussion Starter · #11 ·
AP1 to DC2 Cluster Install
I'm aware theres a pretty good amount of threads based on this out there but I didn't find a really good one for doing the swap that were specifically for DC2 chassis with AP1 cluster. So I figured I'd make a quick Excel sheet to make it as easy as possible to follow:

Those were all the wires I used. I'm sure that if you wanted you could hook up the dimmer to work with the dash lights in the car, but I figured I had a knob which seems easier to use to me than the dash so I just kept the dimmer hooked up to that.

Constant 12V was just tapped into at the fuse box. I use the accessory plug ports in the top of the fuse box for all my add ons such as this cluster.

Everything works perfect with this wiring setup with the exception of the VSS and ECT. I haven't been able to check that wiring yet due to not having the K swapped in yet. From what I've read though with this wiring there should be no need for any converters between the dash and the sensors. Straight plug and play.

Finally got my dual gauge cluster trim in. You get what yo pay for...what can I say. I got the GlowShift version off of eBay. I'd like to see how much better the Autometer version is. Anyone have experience with one? Its twice as much most places but I would have gladly paid it the first time around. It came in STRAIGHT FROM GLOWSHIFT with scratches and molding bubbles on the bezel. I figured I'd let it slide and try getting it in the car. Fitment is less than desireable too. Theres a decent sized gap the whole way around the dash as if it was molded about an 1/8th of an inch sized down from the factory piece. So I would recommend against it if you're pretty picky like me.

Anyways, we had to work with what I had at the time. I told the cluster and bezel to my buddy who does interiors and audio at RPM Hot Rods (The guys who did the Good Guys Giveaway car this year). So this is how the big boys do it that have abilities to create cars above any of mine. We went to happy hour which...oddly enough too a couple hours longer than we anticipated, so we didn't get back to start working on the thing until about 10 oclock so we were in a bit of a rush to get done that night.

Step 1 - Create a trace of the area you want to show the dash with some tracing paper:

Step 2 - Cut out the S2000 cluster template:

Step 3 - Add in a buffer for a "smallest size possible" that the trim piece absolutely cannot be smaller than in order to cover the gap present in the bezel:

Step 4 - Begin getting your cut on:

Step 5 - Next flatten out the new bezel. Use some tape to make a nice guide line to make the cut as straight as possible.

Step 6 - As a quick, easily reversible adhesive that is just full of all around win, use some hot glue to glue the new trim piece to the S2000 cluster. We then hot glued the cluster/trim piececombo to the modified bezel.

Step 7 - Complete! Should come out looking like this. I only had one s***ball gauge laying around while waiting for my new gauges to come in, so I left the other gapping hole out of this picture.

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Discussion Starter · #13 ·
Another part of the swap that is small that is seldom brought up in any build threads out there.

Hybrid-Racing has pre-formed K20z3 radiator hoses which is what I'll be using. I'll also be using the half rad that came with my integra because its already an aluminum rad. As per Hybrid-Racing's hose instructions, I'll be moving my rad to my driver side. I'll then use their hose with a 32mm adapter to plug an aftermarket coolant temp sensor into. A 32mm adapter is required regaurdless (or just a straight piece of 32mm piping) to angle the lower Hybrid-Racing K20z3 hose for the factory style rad. This step can be skipped if you're using Hybrid-Racing or a similar brands side exit lower rad hose radiator.

For a side note from what I've found D series have 28mm rad hoses, so if you're looking at doing this in an EG/EK and plan on keeping the factory rad you'll need a reducer from the K20z3 32mm rad hosing to the 28mm D series radiator.

Next is the heater core hosing. I do plan on keeping my heater core hooked up because its a DD. Currently my engine is up at the builders so I have no real access to it. My friend is also doing a K20z3 swap in his EG though so I had him pull some measurements for me:
For location reference, this is a look at what will be the driver side of the motor. As you can see the upper housing outlet (the one that goes to the IACV, etc) is 17.28MM OD, the lower hard pipe coming from the thermostat housing on the front of the block is a 20.40MM OD. Another issue is that the top housing outlet is angled towards the driver side of the car meaning youll need a quick and heavy bend in any hose you intend on running to our heater cores.

I've come up with a simple way to get around the idea of tracking down reducers since it is difficult to find the proper sizes needed for the swap over the counter. So heres what I'm doing, and I think it'll be almost as cheap and way easier.

I went to Honda and ordered:
79725-SVB-A00 for about 4 bucks. This is the K20z3's factory transmission side water line from the head to the heater core. This has the reduction molded into it that's needed. This will be on the outlet (Drive Side on the Integra) of the heater core. I'm then going to get a straight through 15.75mm joiner to attach this one to the extra bend I'll need.
As for the other reducer I'm still working with my guy from my local Honda to find where the reduction happens on the other line. Should have that within the next week or two unless anyone else knows off the top of their head where that reduction happens in the factory line. I can say its NOT in the straight coupler like it looks in the parts picture. We got that in and measure and there is no reduction. We're ordering in that line that attaches to the motor side next to see if thats where the line reduces.

After that, we should just need a couple 15.75mm hoses to make the last bends to get those reducers hooked into the heater core and well be good!

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Discussion Starter · #14 · (Edited)
Christmas Goodies!!!!!
Got the Hybrid Racing K20z3 Swap Radiator Hoses, Hybrid Racing K20z3 Oil Cooler Hoses (figured do these while the motor was out), and Hybrid Racing Shifter Bushings. All of these are self explanitory why I got them except for the shifter bushing for those of you that have questions about these because I know I did. But with my typical over-research, I decided to go with the Hybrid Racing ones. So heres some info on these bushings and what to look for when looking to purchase a set:

1) Hybrid gives an arguement for one thing about theirs that seems to make theirs better than any other I've seen on the market: They have a spherical bearing in them instead of just being completely solid. This to me (and to their research) has been shown to increase shifter linkage longevity. A completely solid shifter bushing allows only 1 degree of movement while the sperical bushings on the Hybrid bushings still allow the same 2 degrees of movement as the factory bushings while still offering a much firmer shift.

2) As you'll notice the shifter bushings are dependent on different years. I'm using a differen't year transmission (09) and different year bushings (06). So I was concerned with what year I needed to buy my bushings for since theres one set for an 06 civic SI and another set for an 07 + civic SI. The bushings to buy depend on the shifter cables themselves, not the transmission. The diameter of the bushings is different on the 06 shifter cables and the 07 and up cables where as the transmission shifter assembly remains the same diameter on all years.

Hopefully this shows you what to look for. It was enough to settle me on which set of bushings to go with even though there were cheaper ones. As always, the Hybrid stuff came in quick and along with their great customer service. I'm a lifer to Hybrid Racing now!

Heres the latest picture of the motor making it back to my garage finally! Took a quick little shot of it with the winter valve cover and my RB26 in the backround I had to pull out of my 240 to do some transmission work on....

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Discussion Starter · #15 ·
Yeah man you explain everything perfectly, would hate for this thread to die out.since I'm doing the same swap on my del sol I can use the help.
Ask and you shall recieve! That'll give you something to go over for a day or two. Ask me if theres anything specific you can think of and I'll make sure to record it along the way. I was planning to have it done over winter but with having to do the transmission rebuild on my 240 its basically sucked up my car fund until thats done. I'm part time student for one last semester so I'll have no income too. Doesn't look like I'll have this bad boy in and running until summer sometime. It most certainly will be no later than June 2013 though I can promise you all that.

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Not sure if you seen my progress but it's not very much, I'm waiting on the passenger side motor mount bracket due to the holes on the hybrid mounts being too small and don't really want to drill on to them so I ordered en ep3 bracket for 27 bucks and should be here tomorrow.

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Discussion Starter · #17 ·
Hmmm interesting. U mean the hole in the hybrid mount that the bolt goes through to hold it to the frame rail on the passenger side? Like the hole for that bolt is too small in comparison to the bolt itself?

I was looking at doing the innovative ones since they make the hybrid ones and I can get a lower density than the hybrids and get them in a lot more colors for cheaper. So I'm looking at basically the l same mounts u have so the heads up would be grateful.

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Discussion Starter · #20 ·
Yes the holes on the motor mount are too small for the bolts to go thru, here's a better explanation because I really suck at explaining stuff.
Interesting read! Thanks for the heads p! I'll be sure to put that on here when I get to it, or post up how the whole mount assembly looks once u get the other mount in. Little things like that are exactly what I want to be in here!
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