D16y8 Into A D16y7

[civic31g]

Written by Dave a.k.a. VTC_Civic
www.makuragi.s5.com

Well we finally got Gabby to swap an intake manifold from a D16Y8 SOHC VTEC Civic EX onto his D16Y7 non-VTEC engine. Why the swap? Simple, if you ever noticed the shape and design of the Y7 manifold, it's clear that power was NOT Honda's intention. The plenum is very small, and the runners long and skinny. Great for low end acceleration, terrible for high rpm operation. The Y8 manifold on the the hand is a completely different design. A horizontally mounted TB, much larger plenum, and shorter, fatter runners make for a manifold far more efficient at producing high rpm hp. Granted, we're not talking about massive 20+hp gains here, but the difference between the Y7 and Y8 manifolds are truly staggering, and the more we compared the two, the more we were amazed at how well Gabby's Civic actually performed when being forced to breathe with such a handy-cap as that Y7 manifold is. Here are some comparison pics, note the size of the runners and even more astonishing, the size of (or lack thereof on the Y7) the plenum.


Here's a list of what was needed:

D16Y8 intake manifold

D16Y8 intake manifold gasket

D16Y8 intake manifold throttle cable bracket

D16Y8 intake manifold brace

1 tube of RTV sealant

1 can of liquid gasket remover

5' rubber fuel hose

Plastic vacuum line connectors

Basic hand tools including 10, 12, 14, 17mm sockets and wrenches, flat-head screwdriver, Phillips-head screwdriver, needle nose pliers, gasket remover/scrapper.



This isn't really going to be a step-by-step walkthrough of the entire process, rather a general guide as to how we did it. Removal of the D16Y7 intake manifold was very easy. All the vacuum and fluid (coolant and fuel) lines attached to the manifold must be removed. All electrical connectors to the TB and manifold must also be removed. On the cabin fuse panel under the steering column, remove the fuel pump fuse. Crank the car over 2-3 times to discharge the pressure from the fuel lines. Remove the fuel line attached to the fuel rail from the fuel filter. Disassemble the fuel rail components such as the fuel pressure regulator and bracket, and detach the fuel rail from the intake manifold via the 2 12mm bolts under the rail. Gently pull back the rail and pull all 4 rubber injector cushion rings out of their seats on the manifold (injectors should come out with the rail). Remove throttle cable bracket and throttle cable from the throttle plate. Unbolt the TB from the manifold via the 4 12 or 14mm bolts. By this time, pretty much everything should be disconnected from the intake manifold, if anything remains, detach it now. Try to remember where every electrical connector was on the Y7 mani. and correlate it to it's equivalent position on the Y8 manifold. From under the car, unbolt the 12mm nuts holding the intake mani. brace to the block, detach the brake from the block. You can now unbolt the 7 12mm nuts holding the intake mani to the head and slide the intake mani right off.



Now prep the Y8 mani. Because of the wiring differences between the IAC's (Idle Air Controller) on the Y7 (3 wire) and the Y8 (2 wire), you're going to use your Y7 TB on the Y8 manifold. Simply bolt the TB onto the manifold using the same nuts and bolts you removed from the Y7 TB. The TB's are nearly identical outside, and are the same diameter, so don't worry about this hurting your performance any. After attaching the Y7 TB to the Y8 mani., you'll now want to unbolt the 10 or 12mm nut holding the throttle cable plate onto the Y8 TB, and swap it onto the Y7 TB you're going to be using. Don't worry about the spring on the plate, it won't come unwound, just unbolt it, slip the plate off with the spring and swap in onto the Y7 TB. Now here's where things get a little tricky. You have the choice of doing one of two things. On the D16Y8, the IAC valve is bolted onto the back of the manifold itself (horizontally placed cylindrical black/silver piece), on the D16Y7 however, the IAC valve is incorporated into the TB. You can either:

A- Leave the Y8 IAC valve on the manifold itself... or

B- Remove the Y8 IAC valve and plug the remaining holes with RTV as such


The blue stuff you see on the upper right hand of the mani. here is the RTV plugging the two holes where the IAC valve once sat. We later wound out replacing the valve on the mani because the RTV took too long to cure, but it's up to you whether or not to have it there. If you do leave the IAC valve on, make sure to run a small piece of rubber hose as a "U" between the two coolant nozzle's sticking out of the bottom of the valve itself to prevent any vacuum leaks. Make sure to bolt on the Y8 intake manifold brace (black piece at bottom of manifold) to the mani with two 12mm bolts. Back on the car now, you'll notice a short length of rubber hose (spilling lots of coolant when you removed it) attached to a long silverish metal coolant pipe on the back of the engine. You'll need to use a piece of rubber fuel hose here (make sure you buy the same inner diameter as the hole you're replacing) to extend this line to reach around the side of the manifold and attach to the small nipple sticking out of the coolant pipe attached to the lower passenger side corner of the manifold.


You're going to notice a second length of rubber hose, this going to a black box sitting just in front of the large coolant pipe along the back of the engine, this is the PCV valve. GENTLY remove the hose from the valve sticking out of the black box, and place a new piece of hose at least 2' in length, this will attach to the upper most vacuum nozzle on the front of the Y8 intake manifold. Make sure the throttle cable bracket is attached to the intake manifold as well. Lastly, on the lower drivers side corner of the Y8 manifold, you're going to see a very small little vacuum nozzle stocking out of the corner. This was intended as a vacuum source for the cruise control units found only on Civic EX's (D16Y8). Because the Civics with the D16Y7 (CX, DX, LX) did not carry cruise control as an option, this vacuum port is useless, therefore you need to plug it up anyway you can to ensure it is sealed. We used a small piece of rubber vacuum line and jammed a screw in the end of it to seal it.


Ok, by now the intake manifold is about ready to go on. Remove the old intake manifold gasket from the cylinder head. If it's stuck on there, use liquid gasket remover to soften the gasket and a metal scrapper to remove the gasket. Be very cautious not to get particles into the intake ports on the head. We just stuffed them with rags while we worked, and upon completion of the gasket removal, I wiped the insides of the port and top of the valves with a thin cloth. Also when scrapping the old gasket off, be careful not to gash the surface of the head. It's aluminum, so it's soft! Place the new gasket on, position the manifold carefully (make sure to clear the manifold brace running down to the block), use two of the nuts to hold the mani in place while somebody goes under the car to #1- bolt the intake manifold brace to the block, and #2- and perhaps the single hardest part of the entire swap, tighten the center manifold nut. You'll want to remove the oil filter to get to it, you could try to do it from the top with a wrench, but the distance between the #2 and #3 runners are VERY close and it will take an eternity if you do it this way! Lastly, while under the car, push the vacuum line from the PCV valve up through the opening in the center of the manifold (where you tightened the middle nut) and attach to uppermost vacuum nozzle on the front of the manifold as earlier indicated.



Things go quickly from here, but you have to make sure to check everything thoroughly!!!! Ensure that all 7 manifold bolts are on tight (I'm not sure what the factory specs are off hand, but I'd suggest working with a Helms or at least a $10 Haynes shop manual to give you the correct torque specifications. After bolting the mani on, you can replace the fuel rail onto the manifold. Coat the cushion rings with a light coat of clean motor oil and push them into the manifold injector holes, then gently slide the rail and 4 injectors into the manifold. There's not going to be a lot of space between the rail and the bolts that hold it on, so you'll need to gently thread the nuts for the rail on while pushing down on the rail, BE GENTLE!! Attach the fuel line to the rail. Reassemble the fuel pressure regulator bracket and bolt onto rail. Run throttle cable onto the throttle plate through throttle cable bracket. Re attach main (large) coolant line from manifold as well as the smaller hose you extended earlier onto the nozzle next to main line. Finish attaching all vacuum hoses to the manifold as they were removed from the Y7 manifold (brake booster line at the back of the manifold, EVAC/Purge solenoid vacuum line directly under the PCV valve line). When attaching the MAP and TPS sensor clips, be careful not to cross the two. For some odd reason, Honda decided to use the same exact plug for the MAP and TPS, so it's very easy to cross the two. Just note, the IAT (intake air temp sensor, looks like a black probe) should be in the same mini-harness as the MAP sensor, so if you confuse the two, just see which one is tapped together with the IAT sensor. We had to cut some of the tape and wire loom from the harness to give us enough slack to run the injector wires to the drivers side of the car, so make sure you're ready to cut some loom and tape, but be careful not to cut the wires! Chances are, you're going to want to go ahead and extend the wires for the EVAC/Purge unit and #4 injector as Gabby did, but this is up to you. Remember to cover up your wires completely when you're done. Ensure all coolant hoses are properly connected and clamped. Reassemble your intake piping for the new manifold, check the manifold bolts over one more time and ensure they are tight. Reinsert the fuel pump fuse into the fuse panel inside the car, turn the key to the "on" position but DON'T START THE CAR. As you turn the key to on, have somebody inspect and ensure that the fuel lines have been properly reconnected and there are no leaks from either the fuel line to the rail, or the regulator. After triple checking all connections and hoses, disconnect the negative terminal of the battery for about 20 seconds to clear the ECUs memory. Don't forget to fill your radiator up to the appropriate level

Reattach negative terminal, fire up the car! The idle may be a bit odd at first, but that's to be expected. What you want to look out for is jumping idle (up and down in large increments) indicating a vacuum leak, and/or extremely high idle indicating a crossed MAP/TPS sensor. Assuming all is well, allow the car to idle for about 10 mins with the heater on full to bleed the coolant of air. At first the car may have a higher than usual idle, possible accompanied by a small jump (2-300rpm), this is because you have bypassed the coolant line to the IAT. The ECU uses this to determine how cold the engine is and adjust idle until the fluid warms, this happens until the thermostat opens and radiator fan kicks on, at which point the ECU now assumes the car is sufficiently warm and ignores the IAT reading. If you deiced to, you can run the coolant bypass into one of the openings on the bottom of the Y7 TB, and the other opening to the coolant line to prevent such erratic cold idle, this is your choice. Make sure ALL vacuum lines are attached, and that the intake manifold itself is bolted down tight, this will save you the 2 hour headache we spent trying t figure out why Gabby's car would either idle at 6000rpm or jump from 1.5-3krpm. If all is done correctly, once warmed up, shut down the car, check for any fluid leaks, restart the car and adjust idle via the idle adjustment screw on the face of the TB. Turns CCW reduce idle speed, CW increase idle speed. Congrats, you now have a Y8 intake mani on your D16Y7! Because it was raining the day we carried out the swap, we couldn't do a lot of hard road testing, but from the limited testing we did, it was a GREAT improvement fro 4k rpm to the redline, especially in 3rd gear where the DX would fall flat on it's face with the older manifold.

[Smooth_Imports]

Credit for this write up should be given to Dave one of our old members because all of the wording and pictures came from his web site.

[imported_tegs]

Man, don't you ever write YOUR OWN stuff. Quit taking other people's stuff just to make yourself look good. Sorry for the vent but seriously already.



Good write up to whoever it really is.

[imported_comutek]

i fixed it, i think all of the DIYs should have the name/username/website of the original creator at the TOP of the write-up in BOLD.

People spend a lot of time writing these up. They deserve to be listed at the top so that it is 100% clear the DIY was done by them, not the poster.

[tooslow]

For some reason I can not see any of the pics. Can you email them to me please @ gregamber@cox.net ; I would greatly appreciate that.

Greg

[Calesta]

Go to the original site if you want the pictures- people aren't going to just email them to you because you're too lazy to look for yourself.

Yes, Dave is one of our old members- I talked to him last week. He finds it pretty interesting that a lot of the old boards still link ot his articles.