Hybrid.honda-perf.org is a great place for swap info *click here*

D16Z6/D16Y8 engine swap to 88-91 4G/2G civic/crx

text by Mechanic_b
Last updated: April 10, 2002
Sohc vtec engine bay
  • 1.6L D16Z6 92-95 EX/Si (5G) or 96-00 D16Y8 EX (6G) is one of the easiest bolt-on engine swap for your tired 2g crx/ 4g civic 1.5L or 1.6L. With the popularity of Dohc Vtec swaps into 5g civics, there's a lot of sohc vtec motors available out there just waiting for you. It's cheaper than Dohc swaps, availability of the engine, lot's of bolt-on parts and you could even use most of your old go fast goodies from your stock non-vtec engine. Basically you could either just use the long block of a sohc vtec (less modification) or use the whole 5g parts (more complicated). Me ,Mechanic_b and Lagboy chose the easiest and most convenient but effective route which is just using the vtec block, external vtec controller and use the rest of our existing 4g parts. A lot of potential hybrid swappers think that you'll loose performance and reliability of the engine just using the block and not use the rest of 5g parts like ecu, distributor, intake manifold, harness etc. But results speak for itself , with an e.t. of 14.1 @ 94 "all motor" e.t. and 13.1 @ 104 mph e.t. with Nos 60 shot single fogger is much more convincing than saying you have more top end power or I could feel the low end torque much better than my old non- vtec engine, right. Most of the cars we've worked on with this set-up brought home some high and low 14's and even high 13's All Motor, high 12's with single fogger Nos 60 shot. These time slips were done running on slick tires, of course and with just basic bolt-on ( I/H/E ), no P&P head and non-built stock block. Sorry no Dyno results here, my dyno is the 1320ft(1/4 mile). Now Smog Referee Certified even with the use of 4g intake manifold, throttle body, distributor, harness and ecu.

  • Parts list
  • Tools and stuffs needed for the swap
  • Recommended parts to be changed
  • Preparing your engine
  • Preparing your tranny
  • Preparing your distributor
  • Preparing your vtec controller
  • Tech tips

    So here's the list of the parts that you need and options if you're gonna use just the VTEC long block for Dx,Hf or Si model:

  • 1) 92-95 D16Z6 (9.2:1)or 96-00 D16Y8 sohc vtec block (bigger intake/exhaust ports and higher compression (9.6:1)as shown below second and third photo compared to a D16A6 non-vtec block. Notice the combustion chamber similar to 94-up Integra GSR. Beware, 96-00 sohc block are prone to main/rod bearings failure. Most of the 96-00 sohc engine I've worked on had the the same problem. But 96-00 D16Y8 heads are a good VTEC head upgrade to 92-95 D16Z6 short block. It will bump extra compression about .5:1 with the D16Y8 head on D16Z6 short block.
  • 2) 4g Si/EX intake manifold and throttle body IF 1)you already have aftermarket throttle body and p&p intake manifold, 2) you have an Si model to begin with, or 3)the sohc vtec block didn't come with intake manifold or throttle body. Which ever convenient for you.
  • ADDED Due to tons of email concerning dx manifold being used instead of a Multiport injection. The dx manifold tends to have problem to compensate for the extra fuel needed when the vtec activates. Si/Ex Multiport injection manifold, harness ,distributor ,ecu and Throttle body are much more desirable.
  • 3) Or 5g intake manifold & throttle body IF came with the long block.
  • 4) 4g left/driver side engine mounting bracket and engine mount
  • 5) 4g stock Si/Ex/Dx/hf tranny and mounts note: again preferably 89-91 Si model for performance reasons. will explain later.... For tranny mounts upgrade to get rid of engine/tranny flexing toward the fire wall. Get 88-91 civic/crx Energy Suspension mounts insert to stiffen up the mounts.
  • 6) 4g stock axles (DX and Si models are the same except for 4 spd and HF model)
  • 7) 4g Hf,EX or Si distributor for 88-91 PM6 civic/crx ecu or 88-89 PG7 integra ecu ( 92-95 ex/si OBD1 distributor won't work with non OBD PM6 or PG7 ecu, it only works w/ 92-95 ex/si OBD1 P28 ecu and vice versa )
  • 8) 5g or 6g Ex/Si/Vx ignition wires note: 4g ignition wires will work too with slight mods
  • 9) 4g Si/Ex engine harness for Si/EX intake manifold/ecu/distributor or 4g Dx engine harness if you're gonna use 4g Dx manifold/ecu/distributor. If you have DX model and want to use 4g/5g manifold, you need to convert your Dual Port dx harness to Mulitport injection. For DX to Si wire harness conversion click here.
  • 10) 4g Si injectors & fuel rail for 4g harness & 4g intake manifold, 5g EX/Si injectors & fuel rail for 5g manifold. note: 5g injectors won't plug in to 4g harness but you could use it by swapping the 4g injector connectors w/ 5g injector connectors with no problem.
  • 11) 5g or 6g fuel pressure regulator
  • 12) Homemade external vtec controller and 30 amp automotive relay * more info below*
  • 13) 4g or 5g alternator belt depending on what year alternator you'll use. 4g has 3 rib belt while 5g has 4 rib belt.
  • 14) 88-91 civic/crx PM6 1.6L Si ecu (7,500 rev limit)or 88-89 Integra PG7 1.6L LS ecu (7,800 rev limit and the engine runs rich A/F ratio if you use this, good for turbo & Nos)
  • 15) 4g stock clutch kit and flywheel or better , same year as your tranny * more clutch upgrade info below
  • 16) And 4g coolant hoses and heater hoses
    d16a6_port.jpg88-91 civic/crx si intake port
    d16y8_port.jpg96-00 civic ex D16Y8 intake port
    d16y8_combustion.jpg96-00 civic ex D16Y8 combustion chamber

    Tools and stuffs needed for the swap:

  • 1) Honda factory manual for torque specs and wiring diagram
  • 2) breaker bar and flywheel stopper or just air impact to take off the crank pulley
  • 3) torque wrench
  • 4) lot's of metric wrenches and sockets
  • 5) butt connectors or electric tape
  • 6) turn signal bulb and holder with 2 wires ( to check the vtec activation)
  • 7) Dremil tool or air grinder with metal blade/grinding stone for modifying the distributor

    I recommend to change the following while the engine's out & to avoid some head ache later on:

  • 1) 5g/6g timing belt
  • 2) 5g/6g water pump
  • 3) 5g/6g head gasket (clean the pistons and combustion chamber while 'ur at it )
  • 4) 4g/5g/6g intake manifold gasket depending on what manifold you're gonna use


  • Assuming that you already have the engine pulled out of your car, your vtec block is already cleaned up. Install the new intake manifold gasket and then transfer the intake manifold and then torque the nuts at 17 ft. lbs.

  • Transfer the Si or converted Dx to Si harness to the vtec block. On 96-00 block , ignore the (CFK) crank fluctuation sensor located inside the timing belt cover and the knock sensor at the back of the block on 96-00 civic Ex (D16Y8 block). Tip: Don't forget to bolt the ground wire of the engine harness to the thermostat housing or else your engine will not start.
  • Replace the 5g left/driver side engine mounting bracket and rubber mount with the one from the 4g block. Trim the timing belt cover on the front side of the engine underneath the transferred 4g bracket to clear the timing belt cover to the mounting bracket. In order to do this you have to remove the crankshaft pulley and then torque back the crank pulley bolt to 134 ft. lbs.

  • 5g block have the radiator fan switch at the thermostat housing compared to the 4g which is at the back of the block . You could either just extend the two wires blk and yel/green and then connect it using the 5g connector for the fan switch at the thermostat housing or on" 92 block only", there's a hole plugged up by a bolt on the same spot where the 4g switch is located. Just transfer the 4g switch to the 5g block but be careful not to break the two prong connectors and put high temp sealant before installing it.

  • Replace the 4g fuel pressure regulator ( rated at 35-41 psi ) with 5g pressure regulator ( rated at 41-47 psi ). Don't forget to do this upgrade or else you won't have the extra fuel to compensate for the extra air once the vtec activates. This will bolt up to the 4g fuel rail plus with the help of an adjustable clamps 'coz 4g fuel return line is bigger than 5g return line.


  • Si and DX has the same gear ratio from 1st gear to 5th gear except for Hf model which is designed for fuel economy. And one of the significant differences between models are the final drive gear ratio. Si has 4.250 best mated for higher revving powered engine and better acceleration, cruising speed of 3,400 rpm at 70 mph. Dx model has 3.888 , little better gas mileage compared to Si but will slightly hurt your acceleration, 2,500 rpm at 70 mph. Hf has 2.954 (49 st) 3.250 (California) , has the best gas mileage but I don't think you want to swap to 5g vtec and put Hf tranny just for the gas mileage.Click here for tranny gear ratio comparison.

  • If you have an 88 model or tranny, you need to use the same year clutch disc, pressure plate and flywheel to either stock from the Honda dealer around $180 for the clutch kit ( or Clutch masters,ACT, etc) and 'bout $25-30 to resurface the flywheel. Only 88 model trannys have different # of teeth on the splines (21) compared to 89-00 tranny's which have (20).
  • If you have a 89-91 tranny, you could upgrade it even if with just a stock 92-00 Ex/Si clutch disc, pressure plate and flywheel. If you use the 92-00 Ex/Si clutch upgrade, you have to use the Ex/Si 92-00 flywheel. This is a good clutch upgrade if you're on a budget and not only is it larger in diameter which means more friction material, but better heat dissipation and stiffer springs in the hubs to handle torturous aggressive launches and shifting. It didn't show any signs of slippage at the time when I was using the set-up especially when I was "squeezing" considering I was pulling low 13's all day. Tip: while you're at it, replace your throw out bearing because eventually it will cause you some problems if you do not replace it.


  • By using a 4g Si/Hf (they're the same), you need to modify the mounting holes on top and bottom front of the distributor. Ignore the third hole 'coz you only need two bolts to hold the distributor from not leaking any oil and to align the distributor to stock ignition timing as shown on the pix.
  • On 96-on block , the 4g distributor will just bolt right up without any modification .


    There's lots of ways to activate the vtec. You could use a tachometer with shift light from Autometer combined with a 30 amp relay($125) Msd rpm switch ( $55) with Rpm module or module selector combined with a 30 amp relay($59) , Field SFC vtec controller ($250) or just plain ol' toggle switch ($2) but might fry up the vtec solenoid.
  • You don't need to hook up the oil pressure switch for the vtec by the vtec solenoid if you're using the 4g ecu.
  • MSD RPM switch
  • Field SFC vtec controller
  • new! Apex-I V-AFC vtec controller


    TIPS: Now after you've dropped in the engine like just dropping in 4g engine. You'll notice that the driver side mount is a lil' off and tilted to the radiator side of the engine bay. Don't be alarmed 'coz it's normal for this swap. The mounting holes for the bracket is not perfectly in favor to 4g bracket even though it bolts right up. Install the 4g axle and torque the spindle nut to 134 ft. lbs. Double check all fluids (oil, tranny oil, coolant ) check ignition timing, ground wires on the tranny and valve cover and engine harness main ground(-) bolted to the thermostat housing.

    To determine if the vtec controller works, you can either use two wire auto light buld holder with auto light bulb( like the one from your corner turn signal) or use the technique below.

    To use the light bulb, connect it in between the #87 wire from the 30 amp relay and (-)ground. Set the rpm switch at desired rpm (preferably lower rpm for testing only). Start your engine and rev it pass the rpm you've selected at the rpm switch. The light bulb should light up. If not, re-check your wiring from above wiring diagram or ground.

    Or set it at high rpm like "5,200 rpm" at the module selector and then take off on second gear instead of first. Or barely use 1st gear like shift at 1,500 rpm and then pop it on 2nd right away and then floor it. It's gonna lag a lil' bit and might even die but the key here is the floor it all the up to 7,500 fuel cut off. You'll feel a slight pull or G's from 3,500 to 4,400 (lower cam profile)and then drop but once it hit 5,200 rpm (high cam profile) you'll feel another set of G's if the vtec controller works. Sohc vtec low cam profile power starts dropping at around 4,500 to 4,600 rpm so if your vtec is not working , you can tell if the engine is not making anymore power beyond 5k rpm.

    Or you can hook up an l.e.d. light (like the one from your car alarm) "in between" the relay (#87) and the solenoid permanently installed at the desired location , by the instrument cluster or center console to be assured that your vtec works all the time when rev at the desired rpm.

    We set ours at 4k at the track since we launch at 4k to 5k on slick tires of course so that vtec is activated already .But for everyday driving, set it at 4,400 or 4,600 for smooth switch over of the vtec effect. The results might be different on other cars depending on your set-up.

    Good luck and enjoy your vtec powered civic or crx,

    Mechanic_B and Lagboy 1