D15 SOHC VTEC Mini-Me: Write-Up

[simplegreen]

Disclaimer!
This is a write-up based on a 1992 D16Z6 head being bolted onto a 1993 Civic LX with a D15B7 block. This information should be used when performing this swap only, because I do not know how much stuff can be applied when doing mini me's on OBD0 D16A6's and OBD2 D16Y7's.

1. The Victim
A 1993 Honda Civic LX sedan with a puny 102HP D15B7. I chose to do a mini-me swap after reading up on them and hearing that they put out a fair amount of power for how cheap they are. I decided to replace just the head for now because I didn't have the budget or the patience to pull the motor and do the transmission at this time, although it is highly recommended that when one bolts a D16Z6 VTEC head on, they add the short-geared D16Z6 transmission as well for better acceleration. It is widely believed that this combination, with a thin Y8 head gasket, will produce a near 11:1 CR. However, after calculating the compression using the d-series compression calculator, I only came up with 10.1.

2. Shopping:
Well, I started out by getting myself a used D16Z6 head. The head came from a 1992 Honda Civic Si with 145,000 miles. I picked it up for $200 (friends are nice), and that included the head, valve cover, distributor, intake manifold, throttle body, fuel rail, etc. Next, I bought a P28 ECU (from a d16z6) to activate the VTEC from a Honda-Tech member (TD accord you rock) for $85 shipped. After that, I picked up the OEM Honda-Parts necessary to complete the swap. It is recommended that you use the D16Y8 head gasket with this particular setup because it bumps up your compression a tad. My 150,000 mile checkup was soon as well, so I picked up some other goodies.

From 1992 Civic LX 4 Dr:
Water Pump

From 1992 Civic EX 4 Dr:
Distributor Cap
Distributor Rotor
Spark Plug Wires
Valve Cover Gasket

From 1996 Civic HX 2 Dr:
Spark Plugs (These plugs are colder, better for the higher compression)

IMPORTANT: I have read that the VX timing belt is the one to use for this swap because it is for a 1.5L VTEC. THIS IS INCORRECT! The VX timing belt is way too tight, and whines when the engine is at high rpm. I unfortunately did not discover this until the entire head was assembled, so I am now looking for the correct timing belt. I have been told that the Z6 timing belt will fit, so I am going to try that one next. PLEASE STAND BY.

After I collected all of the parts, I got some basic maintenance goodies including 4 quarts of Mobil O, oil filter, coolant, and 2 quarts of MTF.

As far as wiring is concerned, Steve (b16a ferio on this board) made me a custom wire harness for the VTEC, so I can't really explain much about that. I am pretty sure all you need is two plugs that will attach to the VTEC solenoid and VTEC oil pressure wire, some wire to wire the plugs to the wires in the ECU plugs, and some electrical tape to wrap things up.

Grand total spent:
$200 Z6 head
$85 ECU
$250 OEM Honda Parts
$20 misc stuff
___________________
$555.00


3. The Swap
The swap actually went fairly smoothly, until we got to the timing belt. Everything unplugged alright, and everything from new head bolted right up (FYI...the D15B7 and D16Z6 head studs are the same, but the valve cover bolts are not). The timing belt was extremely difficult to put on, but, being the 4th of July, and me needing a car, we stuffed it on there :crook: The tensioner was all of the way loose, and the belt was still tight as hell (I have concluded that the VX timing belt is the wrong one, and that the Z6 one is the correct one and should solve the problem of the belt being too tight). Other than that, everything went well. It really is as simple as unbolting the old head, and bolting the new one on. Of course the intake manifold and throttle body were bolted to my head already, so I didn't have to worry about any of that. For some reason, the spark plug wires that I bought did not fit the D16Z6 head! I ordered spark plug wires from honda for a 1992 Civic EX, so that was one thing that really puzzled me, I guess i'll have to make a trip back to Honda later. Although the B7 head spark plug wires didn't feel like a perfect fit in the Z6 head, they were snug in there and were able to give a spark to the plugs. After everything was bolted up...we plugged Steve's custom VTEC wire harness up, and then plugged the two wires into the ecu plugs...and BAM I had a VTEC head.

4. Driving Impressions
To be honest, the mini-me didn't feel that much faster at first than the stock B7. Low end torque is still the same, which is to say basically non-existent, and with the long-geared D15B7 transmission it takes a while to wind to 7200 RPM. However, the more I drove it and went into VTEC, the car started to feel significantly faster. 2nd pulls a lot harder than before, but both 2nd and 1st take a while to wind to redline. I haven't had the chance yet to test highway acceleration, but because the bottom end wasn't modified, i'm not expecting a miracle.

5. Afterthoughts
Well, the entire swap went fairly smoothly, and with the exception of the timing belt, everything is pretty damn good. The car idled normally initially, then idled very low for about 15 minutes. The problem seemed to fix itself, and the idle problem disappeared. The fact that my spark plug wires didn't work, and that the VX timing belt was the wrong one really casts a shadow over this fairly smooth head swap. Within the next week I hope to get the right timing belt and some well-fitting plug wires so that my mini-me will be fully complete!

SPECIAL THANKS TO:
Sander M. - For helping me every step of the way with this swap and for allowing me to use his garage...thanks man!
Steve N. - For his excellent wiring skills and help during the swap