Brief remarks on installing the D16Z6 itself

Installing a Z6 is pretty close to dropping a D16A6 (a.k.a. A6) engine in. Alterations that need to be made include:

# Driver’s side engine mount: Replacement of the Z6 driver side engine mount with the one from the A6. The mount for the A6 is wider behind the timing belt cover then the Z6 mount, therefore the timing belt has a better opportunity to hit the mount then it should. Therefore it might be wise to grind some of the metal off the mount. This however is up to the person doing the swaps decision. In my personal experience, after running the engine in the car for about 20,000 miles, it looked as if the belt may have brushed against the mount a couple of times but the belt was not damaged. I however did notice that when the engine was running at high speed, the belt’s whipping (at proper tension) brought it very close to the mount. The A6 mount has an “extra” L shaped piece that wraps around from the front of the engine. This piece isn’t necessary and for that matter, doesn’t quite fit on the Z6 (wrong angle). In order to get the timing belt covers to fit over the A6 mount, some cutting of the bottom cover is required.

# Crankshaft pulley: Because the Z6 crankshaft pulley is balanced for the Z6, use it on the Z6. The A6 pulley fits but there’s the potential for premature crankshaft bearing wear because it’s not balanced for the Z6. The belts on the Z6 pulley are a different groove number then the belts off the A6, but it doesn’t seem to matter as long as the belts are tensioned properly. As for accessory over/under turning, no problems have been experienced in the approximately 20,000 miles put on the car since the swap.

#Manifolds: Both the intake and exhaust manifolds used were from the Z6. If the Z6 manifolds are available and aftermarket parts are not to be used, then using the Z6 manifolds over A6 manifolds will give the best result.

• Intake Manifold: The Z6 intake is ported specifically for the engine therefore it’s best to use it rather than the A6 intake manifold. Slight modifications had to be made to the engine harness by transplanting some of the 93 engine harness plugs onto the 89 harness so the intake sensors could be plugged in. Since the MAP sensor on the 93-95 Z6 is on top of the throttle body, it’s necessary to extend the wires for the MAP sensor plug from the 88-91 location on the firewall to the top of the throttle body. Another manifold that is good to use is the D16Y8 manifold. Breathing was improved over the Z6 manifold. This would be a good manifold to source if the Z6 head did not come with an intake manifold.
• Exhaust Manifold: The Z6 exhaust manifold is a 2-piece 4-2-1 design as opposed to the 2-piece 4-1 design used for the A6 manifold. Although the A6 4-1 fits the Z6, there’s no reason to use it over the Z6 4-2-1.

# Clutch, pressure plate, and flywheel: With the exception of the 88 models (see following paragraph), the clutch, pressure plate (pp) and flywheel (fw) for the engine should be used with it. For example, if you have a 93 Z6, use the clutch, pp and fw designed for the 93 engine. While you have the engine and transmission it would be best to replace the clutch and pp.

The 90+ setups have a wider surface area then the 88-89 therefore offering more contact area and more effective power transfer. The Z6 with stock clutch, pressure plate and flywheel will work with 89+ year transmissions. However, due to the 88’s having a different spline count on the input shaft, it won’t mate directly onto an 88 transmission unless the proper 88 clutch, pressure plate and flywheel are used. (Dave's note: some preludes 87 I think used a 212mm disc like the 90+ and had teh 20 splines making the ideal combo for a 88 transmission a Z6 flywheel with prelude clutch)

92+ transmissions can’t be used due because they are hydraulically activated and the mount positions are different then the ones on the 88-91 transmissions.

# The A6 alternator and A/C compressor mounts bolt right onto the Z6 thus allowing the use of the A6 alternator and A/C compressors.

# The location of the coolant temperature sensor is on the back of the block for the 88-92 engines (88-91 A6 and 92 Z6) and if a 92 Z6 is used, no relocation of the wiring is required. On the 93-95 Z6, however, the temperature sensor is on the thermostat cover and the wiring for it will need to be relocated.

This gets the Z6 into the car.

If you decide at this point to use stock CRX Si (A6) electronics, the following steps have to be completed:

Note 1: It is probably wise to replace any o-rings found in the process of doing the swap as they are several years old and most likely deformed thus can cause leaks. The o-rings might be found (for purchase) at local automotive stores or potentially at places that rebuild engines. Most likely the replacement o-rings will be the same color and make sure that the o-ring are suitable for what they are needed for if they are not the same color.

Note 2: If you have a Dual Point Fuel Injection (DPFI) car (Civic STD, DX, LX and CRX STD/DX) you will have to convert your car to Multi-Port Fuel Injection (MPFI.) Conversion information is available on http://www.hybridgarage.com/. Conversion harnesses are available from numerous sources at this point including http://www.hasport.com/.

# Modification of the distributor mounts: When viewed from passenger side, there are three bolts that hold the distributor. 1 top bolt and 2 bottom bolts (left and right.) Only the top and bottom right (toward the front of the car) mount legs on the A6 distributor will be used since the bottom left leg does not match up to the bolt-in location on the Z6 head. Both of the legs on the distributor will need to be modified (cut or enlarged) to get the timing correct. Large washers will most likely be needed to make sure positive contact with the head is made. Make sure to put a new o-ring on the distributor where it goes into the head to prevent oil leakage. It’s also necessary to use Z6 sparkplug wires.

# Fuel Injectors: As for fuel injectors, you must use the A6 fuel injectors with the A6 computer (PM6). To do this, simply replace the Z6 injectors with the A6 injectors. This is another place new o-rings are necessary. The *green o-rings on the fuel injectors should be replaced to avoid the risk of gasoline being forced out around the tops of the injectors and creating a fire hazard. Note: Refers to the o-rings on the injectors where they plug into the fuel rail. While all the o-rings on the injectors I have experience with have been green, both the originals and new replacements, it is possible that they may come in different colors.

# VTEC: In order to use the VTEC, it’s necessary to wire some kind of activation switch for it. Various methods can be used such as a RPM activation switch or an adjustable shift light. Use of a Zdyne 1 Wire VTEC conversion ECU is highly recommended to ease this process. It gives enriched fuel curves for proper VTEC operation and allows a user defined VTEC activation point and other features.

At this point, assuming an activation switch has been wired up, the engine will run like an A6 but will be VTEC capable.

see Ecu Connections if you want to convert to OBD1 .