Building the Naturally Aspirated Honda K Engine Part 3, Assembling the Engine

By Mike Kojima

In the previous two installments of our engine build, you were able to take a look at the parts we will be using to build the bottom end and the cylinder head of our Ariel Atom. Notably, we went with a Dailey Engineering dry-sump system, since the Atom has a lot of aero-enhanced grip, and we want to avoid oil starvation.

We also got rid of the horrible K24 Z7 head and are using a much freer flowing K20Z3 cylinder head. It's CNC ported and prepped by Drag Cartel and stuffed with some of their billet Stage 4 camshafts.

Although we tailored our engine's parts selection conservatively for reliability, we are hoping to make at least 80 more wheel horsepower than the stock K24 Z7. This is in no way all of what the amazing Honda K motor is capable of doing, but compared to other makes of engines with the same level of modifications, the K will amaze you in the ease that it makes power!

So, we will now put our moderate engine together. There are a few details that we are addressing using the right combination of OEM parts to reach our power and reliability goals. Check it out!


Good bearings are essential when building a high performance engine, and like we told you in the introduction to the series, we will be using King XP bearings. We have had extremely good luck with these in many really hardcore racing applications. 

The first step in assembling the engine is to check that the clearances are correct.  

We measured our bores with a bore gauge and our pistons with a micrometer and determined that our bores were fine. We used a fine flex hone to break the glaze on our cylinder walls to help the new rings seat.

Next, we installed the main bearings so we could determine if the bearing clearances were adequate. Note that the interior of the block has been gone over with a die grinder and cartridge rolls to knock off any loose casting sand that could break loose and cause some damage to the engine. 

With the bearings in place and the engines bed plate torqued down, we measured the inner diameter of the bearings and subtracted the crank journal diameter to determine the bearing clearance.

King bearings come in different thicknesses, so we put together some different combinations of bearings to set the final clearance. We do the same thing to the rod bearings as well.  Direct measurement with the proper tools is far more accurate than depending on something like plastigage.

Aluminum blocks grow with temperature considerably, so the normal main bearing clearances are very tight compared to old iron blocks. Some modern ones specify less than 0.001", so you can see how critical this is to maintain oil pressure, control windage, and for long service life. 

After applying some oil to act as an assembly lube, we place the crank into the main bearing saddles in the block. 


Read Part One Here!

Read Part Two Here!

Read Part 3 Here!

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Tuesday, January 17, 2017 8:45 AM
Is there something I'm missing, or did the terminology change while I wasn't looking? I see 2 bolt mains, not 4.
Tuesday, January 17, 2017 10:57 AM
+1 on that, I only see 2 bolt mains. Small detail also, it was mentioned that a Karcepts Throttle Body Adapter was used, however that is not the case. It clearly shows PRL on the top of the plate. I don't think they even make a RBC IM to ZDX TB adapter. Only other one I know of is SiriMoto.
Mike Kojima
Mike Kojimalink
Tuesday, January 17, 2017 11:15 AM
Good Catch, you are right, I messed up on the throttle body adapter and fixed it.
Mike Kojima
Mike Kojimalink
Tuesday, January 17, 2017 11:23 AM
I clarified the point on the main attachment, there are two large bolts that act like traditional main cap bolts but there are two other smaller bolts per main (and sometimes more) that bolt the bedplate to the block that carry a lot of the load as well.
Tuesday, January 17, 2017 3:54 PM
Is that a ferrous insert in the bed plate?
Mike Kojima
Mike Kojimalink
Tuesday, January 17, 2017 6:03 PM
Yes it is.
Thursday, January 19, 2017 9:57 AM
V6 balance shafts? Been looking around for information about deleting it, I'm also building a higher revving M272 engine. I'm simplifying a lot of components and wondering if its even worth deleting? Any info would be much appreciate.

Justin M
Tuesday, January 24, 2017 8:52 PM
"Like the mains, different thicknesses of bearing halves can be swapped around to get the clearances perfect."
Wouldn't that mean that measured from top to bottom there is the correct clearance, but left to right, the tighter bearing half would dominate and the clearance less? Not an issue because it is not on the main force axis where the oil film is required?
Mike Kojima
Mike Kojimalink
Tuesday, January 24, 2017 10:25 PM
It's a common trick that even the OEM's use in factory assembly.
Mike Kojima
Mike Kojimalink
Tuesday, January 24, 2017 10:30 PM
HPGJustin- Balance shafts just affect the shaking moments of the engine, not the dynamic balance of the rotating parts. They are deleted from performance builds mostly because they spin at 2x engine speed so their bearing life can become pretty critical on a performance engine. For instance, if an engine is modded to spin at 9k rpm, the balance shafts will be zinging at 18k rpm! The bearings could fail and the shafts seize which could cause catastrophic valvetrain failure or worse. Also by spinning so fast, they can contribute a lot to windage and frictional losses as well as a lot of heat to the oil.
Wednesday, February 01, 2017 10:04 PM
Thanks Mike, Is this something you would recommend deleting if the car is still street driven on the regular? All the info is much appreciated!!!
Mike Kojima
Mike Kojimalink
Wednesday, February 01, 2017 11:34 PM
If you don't mind the vibration, you can hardly feel the difference.
Wednesday, February 01, 2017 11:47 PM
ha ha, thanks again for the information. Now the fun process starts on the strongest way to delete it.
Wednesday, March 01, 2017 11:26 AM
Where's part 4 this is some good stuff? I just pick a free k24z7 off a friend of mine and would like to build a something close to what your building (not really just it will be for dd and maybe some track time). What do I need to do to put the k20z3 head on? I've looked around online and you guys are really the only people showing any info.
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