This swap is simply a head swap for the 1.5 or 1.6 SOHC engines. If you have a 1.5L or 1.6L non-vtec engine, you will be adding a vtec head from a D16z6 or D16y8. While you're at it you might as well upgrade the intake manifold too. The benefit is upgrading your horsepower. my dx came with 103 stock, and the ex has 127-129 (96-00 1.6L vtec were slightly higher than 92-95).
1999 Y8 Head
A D16y8 will yield higher compression, ~10.5:1 compression ratio, because of its smaller combustion chambers. The CR can also be varied depending on the headgasket you use. A thicker headgasket will give you a lower CR. The Z6 gasket is slightly thicker than the Y8.
Z6 Head Gasket by Mr. Gasket
What does higher compression ratio mean? You'll need higher octane gas. I put 91-92 octane in my Y8 mini-me setup. Also higher compression is not very boost friendly. If you plan on going turbo down the road with your setup, go the lower compression route. High compression ratio is good for naturally aspirated setups. The power increase is through out the whole powerband.
I don't know all the specifics of all the mini-me swap options, but I can tell you all about my combo, a D16y8 head and intake manifold from a 1999 ex being swapped to a 1992 D15b7 block.
A good time to do the swap is when you are due for a timing belt & water pump, I did mine at 135k since I was already going to have the engine half way apart for that maitenence.
I cleaned it up as well for the bling factor:
So what do you need?
- Cyl head from 92-99 SOHC ex or 92-95 si.
- Intake manifold (hopefully this came with your head)
- Distributor (depending on your head combo)
- ECU (P28, not sure about the OBD2 cars)
- Head Gasket
- Use the timing belt that matches the head you will be installing
- Water pump for your block
- Intake manifold gasket
- Throttle Body gasket (although you can probably get by without a new one)
- Spark Plug wires to fit the new head
- Head Bolts or ARP stud kit
- some wire and connectors, possibly a few other misc items from the hardware store.
- Service Manual (for all the specifics, don't start without one)
1. Make sure the Engine is at Top Dead Center (see service manual) Drain the coolant and oil so you will not have a mess later on. Unbolt the header from the head.
2. Disconnect all hoses, sensors from the head and throttle body, also unhook the throttle cable and tranny cable if automatic.
3. Take note and mark where your distributor is positioned, then remove it and the plug wires.
4. Take off the valve cover & upper timing belt cover. Unbolt the 10 head bolts in the pattern described in the Service Manual.
If you are changing timing belt and water pump as well:
- take off accessory belts
- Remove crankshaft Pulley using an impact wrench. Be careful not to lose the Woodruff Key (little square metal piece in the notch on the crankshaft)
- take off plastic timing belt cover
- loosen belt tensioner
- be sure engine is at Top Dead Center (see service manual)
- remove timing belt
- remove water pump & replace
- put new belt on loosely for now
Pull the head & intake manifold from the block.
Remove the oil control jet from the block, the vtec head does not need it. This is located on the top surface of the block between the #2 and #3 cyls, it comes out with a pair of needle nose pliers.
Scrape all of the old gasket from the mounting surface of the block, trying not to get any in the coolant jackets or cyls. I used a shop vac to suck any pieces out of the cyls.
Now is a convenient time to change your oil filter!
there are 2 holes in the bottom of the head, When I pulled the D15b7 stock head off, there are 2 dowel pins that were in the head. They go into 2 of the bolt holes on the block to make sure everything is aligned and the head gasket in the proper place. Well the Y8 head I got did not have the pins and I did not know what they were so I figured they weren't needed. I have never had any problems... but since then, while removing a head from my other civic, I found that they are on the Y5, Y7, and Y8 heads as well as the Z6 and B7 heads. They are only a couple bucks from the dealer, replace them for a piece of mind.
I used the Z6 head gasket from Mr. Gasket. It is a Multi-layer Steel gasket. It was about $45, or you could save a few bucks and het the oem one from the dealer. The Z6 head gasket is slightly thicker than the Y8 one. If high compression is your goal then the Y8 will be what you want. The Z6 will not give you as high of compression, but lower compression will allow you to use a lower octane and be more boost friendly (although the compression of this setup with either head gasket is high for boost)
Head Bolts. This is a grey area for me, my solution is not the best but when I was doing this swap in 2002, it was the only option. I had a Y8 head to I figured I should use the Y8 Bolts... Nope most of them were too short, only the 2 in the back corners reached. All 10 Y8 bolts were something like $28. So back to the dealer I go to buy D15B7 Bolts- they were almost $9 each! The D15b7 head bolts are stretch bolts, meaning you should not re-use them. So I went to Summit Racing and got an ARP Head Stud Kit for the D16z6 (the only one they had for SOHC civic at the time). And they worked, except for the 2 bolts in the back corners! So I used 8 of the ARP studs and then 2 of the Y8 bolts for the back corners. This has not caused any problems at all.
headstuds, the 2 rear corners required Y8 headbolts
Y8 Intake Manifold is the best flowing intake from Honda for the SOHC Motor. the Y5 intake manifold from the civic HX looks similar to the Y8 but it has an EGR (exhaust gas re-circulation) valve incorporated into the runners of the #2, #3, and #4 cylinders. You don't want that. The only extra step is finding a place to install your AIT (air intake temperature) sensor. The AIT sensor was located on the back of the #2 runner on the stock manifold, but the Y8 manifold has no bung for it. You can either extend the wires and drill a hole in your rubber or aftermarket intake tube, or drill a hole in the back of the #2 runner as I did. Apply some JB weld and stick it on.
I also had to trim the "feet" on the bottom of the runners to clear the mounting bracket on my D15b7.
Another important note is that the 99-00 Y8 had what Honda calls "Cold Start Assist" I found out my intake Manifold wad from a 99 when the Intake Manifold gasket I got for a 96 left a huge vaccum leak between the head and manifold. The Cold Start Assist has 4 tiny holes on the flange of the manifold, which go to a vacuum line leading to the thermostat housing. I did not even try to bolt the Y8 thermostat housing on my D15b7 Block. I capped off the plugs on the intake and called it a day. I'm not sure if this was the right solution, now my intake makes a significant hissing sound as soon as I put the car in drive (yeah its an automatic... for now).
I also had 1 extra coolant line, probably something to do with using my stock thermostat housing. I just spliced it into another line with no problems.
The hissing might also be the result of using an intake manifold from a manual civic. It did not come with a throttle body, but the all the SOHC throttle bodies are 55 mm so I used my stock one. I also had to hack saw part of the back of the intake manifold to get my stock IACV (idle air control valve) to fit. I mentioned above I had a vacuum leak after the swap, so I put one on from a D16z6 because the symptoms of a vacuum leak are the same as an IACV not functioning properly. Later I found the leak and after I fixed it the engine idled fine. So I'm not sure if I needed to use the D16z6 IACV or if the stock one would have worked fine. I do know that the OBD2 IACV's are manual/automatic specific. The manuals have 2 wires where as the automatics have 3. (the automatic IACV can be spliced into 2 wires easily though.)
Unless you can twist your arm into engine compartments as I can, I suggest bolting the intake manifold to the head before putting the head back on.
Torque the head bolts or studs to specs and order specified in the manual or instructions with the stud kit.
Water Pump. I researched and read that the D15b7 pump had 27 teeth while the Si pump had 29 teeth. The 2 extra teeth would mean less resistance on the accessories which would mean a little less power loss. However the Si pump did not fit so I used the D15b7 pump with no problem.
Re-assembly time. Be sure everything is at TDC. slip the timing belt over the cam gear and tighten the tensioner. Crank the engine by hand and check to be sure the cam gear and Crankshaft pulley are still both at TDC
The D15b7 Distributor will fit the Y8 head, however it will not fit the Z6 head. I see questions and wrong answers about this all the time. Why Honda made the Z6 bolt pattern different I don't know, but you will only get one bolt attached if you try with a B7 Distributor. If your Y8 head came with a Distributor, it will have the OBD2 harness on it and wont plug into your OBD1 harness without much modification. So if your mini-me swap is with the Z6 head, get a D16z6 distributor as well. Also the D15b7 plugs will not fit right on the Y8 head, so get some Y8 plugs.
The distributor will only go on one way because the part of the shaft that connects to the cam is slightly off center, so no need to worry about putting it on 180? backwards.
Your stock ECU will not know what to do with a VTEC head installed. The wrong way is to install a switch or RPM activated switch to actuate VTEC. These switches are not able to adjust the fuel curves like an ECU should. So spend ~$100 and buy a P28 ECU from a 92-95 Si or EX. Get one from a car that has the same type of transmission as yours. (It's possible to convert an ecu to work on a different transmission, but requires very precise soldering.) The P28 will plug into your factory harness. If your car is automatic (as mine was) be sure to get a P28 from an automatic Ex.
Once you have everything back together it is time to install the new ECU and additional wiring for vtec. The ecu is behind the carpet on the outside passenger foot area. Looking at the ECU pinout, you'll need to run the vtec solenoid to the A4 pin.
Vtec solenoid on a stock D16z6
There are 2 wires on the Oil Pressure sensor.
on a stock D16z6
The black wire is ground, orange goes to D6 on the ECU
Looking straight into the back of the sensor, the wire in the bottom of the pic will run to the D6 pin on the ecu, the top wire is just run to the chassis as a ground. Just be sure you have the sensor the right way when determining the D6 wire from the ground, hold it and compare the tabs on the outer edge to those in the pic. Use some connectors and heat shrink, do it right. If you can't get the harness clips to connect to the sensors, you can use a small butt connector and cover it with silicone as I did. I filled that back area of the sensor with silicone to make it weather proof.
Here is where you wish you had a 1992 hatch. All 92 hatches were pre-wired for vtec up to the passenger shock tower. Just look at the color of the wires for the A4 and D6 pins on the ecu and find them at the shock tower. Tap into them there and connect your sensors. Otherwise you will have to run the 2 wires through your firewall to your ECU.
I had to slightly trim the top section of the timing belt cover to fit.
You're all done now. Double check everything. If you start the car and it revs up and down, you probably have a vaccum leak.
When I did mine using the Y8 manifold, The positioning of the throttle cable bracket kept the throttle body from opening all the way under full throttle, never revving high enough to experience VTEC. The remedy for this was to adjust the cable under the dash, where it meets the pedal. The slack was removed and everything worked perfect!