Bienvenidos to part 3 of our journey to build an “Everyman” 1.5L Honda turbo engine capable of supporting 400 WHP. In our last blog (part 2) “we started from the bottom now we here”. Part two covered the lower part of our engine block build going into detail on the rods, pistons, oil pump, crank, etc. In this blog, we take you up top and explore the cylinder head and valve train and wrap up the build. 

Before we get started it's worth mentioning again that we are building the Everyman engine. We did our best throughout to build an engine with readily available parts that do not cost an arm and a leg to acquire. So with that let us dig in.

We will strategically work our way up from the deck of the cylinder head (where our short block ends and our long block begins). Starting with the head gasket there are really only two options here. Do you stick with OEM or go with the one from Cometic? The Cometic head gasket is a nice piece but in this case, we stuck with OEM. We have learned that the OEM head gasket is not really the weak point. Nearly every case of a “blown head gasket” that we have seen was not because the head gasket failed but rather because the cylinder head lifted from loss of clamping (head studs). 

So that leads us to our first upgrade, HEAD STUDS. We upgraded to some ARP Head Studs. Now as of this writing, ARP does not have a specific kit for the Honda L15 engine. However, we have found that ARP Kit part #271-4701 works for our engine. This kit is actually for a Suzuki GSX 1300R Hayabusa. Yes, you read that correctly, we used a head stud kit from a motorcycle for our tiny little engine. But it works “mostly”. Let us explain.

In order to use that ARP head stud kit we need to run some spacers. The head studs supplied in the kit are about 10mm too long. The spacer allows for proper clamping onto the cylinder head. MAPerformance has a kit that combines the ARP Hayabusa kit and the required spacers in one easy-to-purchase package. This kit has everything you need for a successful upgrade of the head studs and ensures that when pushing north of 32+ psi we won’t lose a head gasket due to the cylinder head lifting.

Moving up the head we make our way to the intake and exhaust ports of the cylinder head. It is not an uncommon practice to see builders start to go wild on cylinder head porting for built engines and in many cases that has its place. Not with our build! Why? Well, really it comes down to two things. First, we are reusing the OEM camshafts. Second, we want to keep the integrity of the cylinder head

1. A crazy ported cylinder head that operates with OEM camshafts does not really make much sense. When you spend the time to open up the ports, clean up the bowls, and make everything smooth it's normally because you are stuffing a big cam into your car. The bigger cam gives longer duration and more lift than the OEM cam and your porting exploits that. They work together to take in as much air as possible to help increase volumetric efficiency with the goal of making more power. Keeping our stock camshaft profile does not really merit us touching the head.

2. The single port around the exhaust head is pretty close to some cavities and water jackets. We don’t want the porting to be cutting into those and making them too thin. For that reason we keep the OEM ports untouched for the Everyman build.

Rounding off our cylinder head upgrade is a set of performance valve springs, keepers, and retainers. These parts replace the OEM components and seal up right over our OEM intake and exhaust valves. These are made of high-grade silicon alloy and have a greater seat pressure than OEM. We upgrade our valve springs because, with the bigger turbo, we want to carry the RPM on the engine out further. OEM redline is 6500 rpm. With basic tuning on a stock engine, we can get away with 7000 rpm. However, we know the W series line of turbochargers can keep on delivering the boost well into 7500 rpm so we need the hardware to support that. If we tried to maintain those high rpms on stock springs the OEM valves could float and cause some serious head damage. To put our minds at ease we went with the full kit from Brian Crower that can be had for less than $300 bucks. These springs are not too soft or too stiff and are just right for this build.

With that last piece of the puzzle in place, our engine is finally ready to come together. We marry the top and bottom half together and then drop in this fresh build into our nice and clean engine bay. Then we load up our new engine with every 27WON bolt-on you can imagine. CAI, FMIC, Full Exhaust. TIP, I mean the works all in the pursuit of 400whp. Oh and remember that big surprise that I mentioned back in design blog part 1?

With the combination of 91oct and E30 along with some outstanding tuning, and our biggest turbo yet the W3 we safely eclipsed the 400whp mark as measured on our Dynapack dyno. Our built engine can take this horsepower and torque without even trying and with more fuel and turbo pressure we can take it well beyond the numbers you see in the graph below. The Everyman engine can take this extra pressure and is an engine you can easily build for yourself.

Side Note: We developed this engine to test the biggest turbo we’ve developed, the W3. The W3 is now available to purchase right here. While the W3 is a great turbo, it’s not for everyone. Looking at the graph below, you can see it sacrifices low end spool for some major top end. It’s really meant for drag, roll racing, or someone who just wants a massive drop-in turbo for bragging rights!

It’s worth remembering that in order to get 400whp on the L15 you not only need a built engine but you also need the right turbo, the right tuning solution, and adequate amounts of fuel. It’s our hope that you have found this series of blogs useful and we can’t wait to make power with you!!!

Vincent 
Co-Founder