Welcome to my D15 SOHC VTEC Mini-Me Writeup!
This is a write-up based on a 1992 D16Z6 head being bolted onto a 1993 Civic LX with a D15B7 block. Like Spade’s SOHC Upgrades thread, this is a continual work in progress. If you are thinking about doing a mini-me swap on your 92-95 Civic using a D16Z6 head, then this is the place to be. I will do a complete walkthrough of the mini-me, including a shopping list of parts, tools needed, how to perform the swap, important things to look out for, what to expect when you finish, and ideas for future modifications. These instructions are for 92-95 Civic D15B7 DX, LX mini-me’s, but most of the stuff can be applied to CX’s with pistons with reliefs for 4 valves as well. If you have a question about doing a mini-me on a non-OBD I car, you can PM me and I’ll see if I can help. Note: DO NOT ATTEMPT THIS SWAP ON A CIVIC VX, THE PISTONS HAVE TOO LARGE OF A DISH AND THE COMPRESSION WILL END UP BEING TOO LOW.
Well…enough already let’s get to it!
1. What exactly is a “mini-me”?
A “mini-me” is an informal name for a D-Series SOHC VTEC head mated to a D-Series SOHC non-VTEC block. Most mini-me swaps consist of D16Y8 or D16Z6 heads onto USDM D15B, D16A6, or D16Y7 blocks. JDM D15b VTEC heads will work as well
2. Why should I do a mini-me swap?
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. It is widely believed that this combination, with a thin D16Y8 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 10.1:1. To bump the compression a few more tenths, you can remove the middle layer from the Y8 head gasket. Theoretically, a stock mini-me with a Y8 head gasket should put out about as much power as a D16Z6, give or take a few horses. The raised compression makes up for the difference in displacement.
3. Okay, what parts do I need to buy?
For a Z6 mini-me swap you’ll need four basic things: a D16Z6 cylinder head (including valve cover, distributor, spark plugs, spark plug wires etc), D16Z6 timing belt, D16Y8 head gasket (D16Z6 works well also, but Y8 is a better, metal gasket) and P28 ECU (make sure you get an auto ECU for an auto, manual for manual).
Several places on the net and several people on Honda-Tech say that the VX (D15Z1) timing belt is the one to use for this swap because it is for a 1.5L VTEC. THIS IS INCORRECT!
When I did the initial head swap, I used a VX timing belt. The VX timing belt was WAY too tight, and whined when the engine was at high rpm. I unfortunately did not discover this until the entire head was assembled. The VX timing belt has 103 teeth, where as the Z6 timing belt has 104 teeth, and the B7 belt 106 teeth. I was finally able to replace the VX timing belt with the Z6 timing belt, and the Z6 timing belt fit much better and didn’t whine. THE D16Z6 timing belt is the correct belt to use with a B7 block / Z6 head combination.
Note also: The D16Z6 and D15B7 spark plug wires are NOT interchangeable. You will need D16Z6 spark plug wires with this swap. Also, the 96-00 Civic EX’s have a 9.6:1 compression ratio, so the spark plugs from that motor will better with the higher compression than the stock Z6 ones. Honda Part # 98079-5614P, NGK ZFR6J-11.
You can use your stock intake and exhaust manifolds with the mini-me. All d-series manifolds are interchangeable. However, both the D16Z6 intake manifold and header flow much better than the D15’s…so if you can pick them up for a real cheap price, then definitely go for it. In addition to the main things, you’ll need little things, coolant and wire (to wire the VTEC solenoid and oil pressure to the ECU).
I however, wanted to make sure that the swap ran perfectly once I got it running so I picked up a few general maintenance things as well, such as a new distributor cap and rotor, new water pump, new spark plug wires, and a new valve cover gasket.
List of Parts:
D16Z6 Cylinder Head (Including distributor cap, valve cover, plugs/wires, VTEC solenoid, etc)
D16Z6 or D16Y8 Head Gasket
D16Z6 Timing Belt
Wire and plug for VTEC oil pressure switch
D16Z6 Intake Manifold
D16Z6 Exhaust Manifold
*If you remove your manifolds, make sure you get new gaskets
Water Pump (for the block you are using)
Spark Plugs (EX D16Y8)
Spark Plug Wires
Valve Cover Gasket
Distributor cap and rotor
I spent about $550 total when all was said and done. I paid $200 for the head, and $85 for the ECU. Random stuff kept adding up after that. $550 is comparable to a full Z6 swap, but remember this included a new timing belt, head gasket, etc.
4. What tools will I need to do the job?
Well, 95% of the job can be done with a 3/8 inch ratchet, 10-19mm sockets, and a set of screwdrivers. However, you will need a torque wrench so that you can torque the head bolts down correctly, and you will also need access to an air wrench when you do your timing belt to get the crank pulley off. You will also need wire cutters, and some electrical tape for the wiring part.
5. Okay, I got all of the parts and tools, now how do I swap the heads?
Alright first what you’re gonna need to do is remove the cylinder head.
Here are the step by step instructions on how to take your head off (Taken from helms. I recommend you have the actual manual in front of you because it includes detailed pictures and diagrams):
1. Disconnect the negative terminal from the battery.
2. Drain the coolant.
3. Relieve fuel pressure (take the gas cap off)
4. Remove the air flow tube (intake)
5. Remove the fuel feed hose and charcoal canister hose from the intake manifold.
6. Remove the throttle cable at the throttle body.
7. Remove the throttle control cable from the throttle body (A/T only).
8. Remove the fuel return hose and brake booster vacuum hose.
9. Remove the engine wire harness connectors and wire harness clamps from the cylinder head and intake manifold (Basically any hose or plug that’s connected to the intake manifold or head, needs to come off)
10. Disconnect spark plug wires at spark plugs and remove them from the distributor.
11. Remove the engine ground cable on the cylinder head cover.
12. Remove the power steering belt and pump (Do NOT disconnect the hoses)
13. Remove the power steering bracket (4 bolts)
14. Remove the emission vacuum hoses and water bypass hoses from intake manifold assembly (included in step 9)
15. Remove the radiator upper hose and heater hose from the cylinder head (included in step 9)
16. Remove the water bypass hose from the thermostat housing.
17. Remove the intake manifold bracket.
18. Remove the self locking nuts and disconnect the exhaust manifold and exhaust pipe A.
19. Remove the exhaust manifold bracket.
20. Remove the PCV hose, then remove the cylinder head cover.
21. Remove the timing belt upper cover.
22. Loosen the timing belt adjusting bolt 180 degrees to release the belt tension.
23. Push the tensioner to release tension from the timing belt, then retighten the adjusting bolt.
24. Remove the belt from the cam pulley (gear)
25. Remove the cylinder head bolts, then remove the cylinder head (loosen bolts starting from the outside, then coming in).
If you have a D15 block (or any D-series block with an oil jet for that matter), you need to make sure that you remove the oil jet between cylinders 2 and 3 when you do this swap. If you don’t, you won’t have VTEC. I forgot to pull the oil jet out the first time. You won’t get a code, your ECU will say your solenoid is fine and everything is working great but VTEC will not actually engage. Make sure you remove the oil jet. I took a screw, screwed it into the oil jet, and then pulled it out with a pair of pliers.
After you’ve pulled the oil jet, you’ll need to sand down the block surface so that no gasket is left caked on the block. (You won’t have to worry about this anymore because hopefully you’ll be using a Y8 metal gasket). If you get shavings in the cylinders, then fill the cylinders with warm soapy water and float the shavings out. You’ll do this by turning the crank over a few times with a 17mm until all the water is out. Make sure that there is NO liquid in the cylinders or head bolt holes when you put the head back on (If there is, you can crack your block when you torque down the head bolts). If you are using the manifolds from your stock motor, all you’ll need to do is unbolt your intake manifold (with throttle body) off of your old head so that you are ready to put it on the Z6 head. It’s only 8 bolts.
Now, let’s put your new head on (Taken from helms. I recommend you have the actual manual in front of you because it includes detailed pictures and diagrams):
-You can reuse your D15B7 head bolts with the D16Z6 swap…they are the same size
-Always use a new head gasket
-If you are using your old intake manifold with the new head, make sure you use a new intake manifold gasket, same goes for throttle body. If you removed it, you need a new gasket.
-Cylinder head and engine block surface must be clean (no water or dirt…even in the head bolt holes)
-Turn the crankshaft so that No. 1 piston is at TDC.
1. Install the intake manifold and tighten the nuts in a criss-cross pattern in 2 or 3 steps, beginning with the inner nuts.
2. Install the exhaust manifold and tighten the nuts in a criss-cross pattern in 2 or 3 steps, beginning with the inner nut.
3. Install the exhaust manifold bracket.
4. Install two dowel pins, head gasket, and cylinder head
-Apply clean engine oil on the bolt threads and washer contact surface
-Always use a new cylinder head gasket
-Turn the cam pulley to TDC before installing
5. Install the bolts that secure the intake manifold to its bracket but do not tighten them yet (optional, I decided not to do this because the intake manifold bracket is a bitch to get to)
6. Tighten the cylinder head bolts in two steps, working your way from the inside bolts to the outside bolts.
-Step 1: 22 lb ft
-Step 2: 53 lb ft
7. Install the exhaust pipe A on the exhaust manifold.
8. Tighten the bolts for intake manifold bracket (again, optional)
9. Install the exhaust pipe A on its bracket
10. After the installation, check that all the tubes, hoses, and connectors are installed correctly.
11. Adjust the valve timing.
12. Apply liquid gasket to the head mating surface of the number 1 and number 5 or number 6 cam holder then install the cylinder head cover (you can neglect this because you need to leave it off for the timing belt install)
13. Install air intake.
14. Fill radiator with coolant.
Alright, we’re getting there. Now all we have left to do is the timing belt, and the VTEC wiring.
timing belt and water pump replacement thread by Poison, GREAT info:
Lets do the timing belt first (Taken from helms. I recommend you have the actual manual in front of you because it includes detailed pictures and diagrams):
1. Remove the splash shield
2. Remove the power steering pump (should already be done)
3. Remove the A/C compressor adjust pulley with bracket and the belt (with A/C), then remove the alternator belt.
4. Remove the P/S bracket (should already be done)
5. Loosen the alternator adjusting bolt and pivot nut, then remove the belt.
6. Remove the cruise control actuator and the P/S tank bracket.
7. Remove the engine support nuts. Loosen the mount bolt and pivot the engine side mount rubber out of the way.
8. Remove the cylinder head cover (should already be done).
9. Remove the timing belt upper cover (should already be done).
10. Remove the special bolt and crankshaft pulley (you NEED an air gun for this).
11. Remove the timing belt lower cover.
12. Loosen the timing belt adjusting bolt 180 degrees to release the belt tension (should already be done).
13. Push the tensioner to release tension from the belt, then retighten the adjusting bolt.
14. Remove the timing belt from the pulleys.
I recommend that since you are replacing your timing belt, you go ahead and replace the water pump as well. It is not that expensive, and is only a few bolts. If the water pump fails, you can kiss your motor goodbye so it’s a good thing to get.
Okay, now that you’ve taken the old timing belt off (and hopefully put a new water pump in), lets put the new timing belt in (Taken from helms. I recommend you have the actual manual in front of you because it includes detailed pictures and diagrams):
1. Install the timing belt in the reverse order of removal; only key points described here.
2. Position the crankshaft and cam pulleys at TDC.
A. Set the crankshaft so that the No. 1 piston is at TDC (top dead center).
NOTE: Align the groove on the teeth side of the timing belt drive pulley to the lower arrow pointer on the oil pump.
B. Align the TDC marks on the cam pulley with the pointer on the back cover.
3. Install the timing belt.
4. Loosen the adjusting bolt, and retighten it after tensioning the belt.
5. Rotate the crankshaft (w/ 17mm socket) about 4 or 6 turns clockwise so that the belt may fit in the position on the pulleys.
6. Adjust the timing belt tension.
7. Check the crankshaft pulley and the cam pulley at TDC.
8. If the cam pulley is not positioned at TDC, remove the timing belt and adjust the positioning.
Make sure you adjust the tension the alternator and A/C belts, as well as the power steering belt. Look over everything and make sure it all looks good, because you’re almost done.
6. I’m done swapping the heads, now how do I make my VTEC work?
The P28 ECU plugs right in, you all you’ll need to do is wire the VTEC up. First, you’ll need to get an engine plug from a junkyard for the VTEC solenoid oil pressure.
You’ll need to run the blue wire (or whichever color is from the plug) to pin D6, and then run the black ground wire from the plug to anywhere on the motor. You then need to run the green wire from the VTEC solenoid to pin A4.
THAT’S IT! YOU’RE FINISHED! Make sure you’re not throwing any CEL’s, if you are, go back and check your work.
7. How much faster will my car be once it is done?
Well, my car definitely felt much better overall. The lower end will be a bit torquier, and your car will pull much better in the higher RPM’s (5000+). I feel the most difference on the highway, having the extra HP is very nice when you need to merge. The one downfall to a mini-me is the long transmission. The DX transmission is much longer than the EX, and the VX/CX is even worse. I did some calculations, at 7200 RPM here are your shift points with respective transmissions (using 195/50/15 tires, stock tire size):
46 - 85 - 140 - 175
37 - 68 - 102 - 132
35 - 60 - 91 - 126
The gear ratios were taken from Mista Bone's tranny page. Emerika stated that the EX transmission shaved 7 tenths of a second off of his quarter mile time in his hatchback, you DEFINITELY want to get the EX transmission
I was finally able to run my mini-me in the quarter mile. As you can see, with the VTEC working and with the 20” tires (as well as some better driving) I was able to pull off a 15.9@86, a full second faster than with the B7 with I/E. I know my motor has even more potential than this because that run was with the long *** DX tranny
1993 Honda Civic LX Sedan (Weighed in at 2320 lbs without driver)
D15B7 Block and Tranny
D16Z6 Head / Intake Manifold / Exhaust Manifold
Full Interior with Spare Tire, Tools
Short Ram Intake w/ removed headlight
Welded-on straight through eBay muffler
Stock Cat/Exhaust Piping
Original Clutch w/ 160,000 miles
No PS belt
175/50/13 All-Season tires on 13" VX Wheels @ 23psi
8. The mini-me is nice, but I want to make it even faster. What mods should I consider?
The number one modification you should do is the EX transmission. You can pick one up in the Honda-Tech classifieds or in a junkyard for about $200 bucks. They are worth their weight in gold. The usual intake/header/exhaust combination works very well. Exospeed, ZEX, and Skunk2 make very good SOHC VTEC camshafts that will add a good bit of power as well. If you want to take it even farther, you can use D16A1 Integra pistons (P29) that will put your compression way into the 12’s.
For more info on SOHC upgrades, click here - http://www.honda-tech.com/zerothread?id=335078
Sander and Steve of Mixed Motorsports for all of their help
MistaBone for knowing everything and helping me whenever I had a question
Spade for all of his knowledge
Poison for his awesome timing belt / water pump writeup
Comments/additions are welcome