Checking and Adjusting Valve Gap

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[BSD, KJ] Special tools required: parts 07MAA-PR70110 and 07MAA-PR70120, about $70 total if you get a discount. One part is a deep socket with a hex end so you can turn it with a wrench from the top end. The other is essentially a stubby flat-blade screwdriver that fits into the socket. My opinion is that yes, you do need the special tool. I tried a socket with a screwdriver inside and it was almost impossible to get the screwdriver to fit in the slot (screw). Further, you need to set the gap, then measure, then reset, remeasure, etc. It is an iterative process and any extra effort or time delay required to adjust each valve is multiplied by 24 times the number of iterations it takes to get the valve set correctly. You do the math. The special tool is well worth it.

Highly recommended: NSX service mat 07MAZ-SL0000A, about $100 discounted.

Start off by letting the engine cool a bit. You don't want the engine very warm to start with and the real adjustment (and all head work) needs to be done when the heads are at 100 deg F or less.

Drape the back of the car with the NSX service mat. The first scratch you don't make will pay for this handy item. It also allows you to neatly arrange the many parts you will remove on the trunk lid. The mat has a hole for the antenna if you decide to listen to the radio or CD while you work. :-)

Jack up car, remove right rear wheel (passenger side).

Remove coil covers and valve (head) covers: There are 4 bolts and 2 cap nuts holding on the coil cover. Remove them. The coil cover will now come off. Then, remove 2 brass-colored cylinders on the middle stems that had the cap nuts on them. (That part isn't in the book.) Next, remove 4 cap nuts holding on the head cover. On the driver's side of the front valve cover, remove the bolt which holds a metal bracket supporting a large wire harness.

Disconnect wires running along passenger side of valve covers. All wire connectors in the engine area (and possibly elsewhere) appear to require pinching a small plastic lever (compare the one on the fuse box cover) until it clicks, then pulling apart the connector.

On front side, you should remove 2 plastic covering parts first so you can get at the 2P (two-pin) connector. Remove 2 bolts for each coil. Then, pull coils up and disconnect connector. Remove coils completely and tuck coil wires out of the way. Pull out the hose/plug in front side head cover. Disconnect air hose running from rear head cover at head cover.

There are 2 more 10mm nuts down on those 2 center shafts on each side. Use a deep 10mm for them and remove the nuts. Then, remove 6 washer/seals on 4 corner post and 2 center posts. You might have to gently pry them loose with a screwdriver. Remove shock tower brace (two 12mm bolts on each side).

Remove bolts holding clump of wires that runs along side of the rear bank (passenger side). This will make it easier to get the head covers off. Remove head covers. The rear one comes out best with the driver's side coming out first.

Now you are ready to adjust the distance between the cam lobes and the plates that it pushes to open the valves. But, you have to find Top Dead Center (TDC) for each cylinder first. To do this, look at the front cam gears. The rear side gear will have a number and an arrow that represents each gear. When the arrow next to the number is pointing right at the center of the front cam gear, then that cylinder is at TDC. The arrow will point right along the timing belt cover which is still on the car. Put another way, when the number on the rear gear has been rotated so it is closest to the front gear, you are there. You don't have to be perfect here because both valves have been closed for 1/2 a revolution when at TDC. To rotate these gears, put a 19mm socket on the crank shaft nut. This is why the rear wheel is off. Rotate CLOCKWISE ONLY, or you risk slipping a tooth on the timing belt.

Once you get one of the cylinders at TDC (doesn't matter which you start with) you are ready to adjust. From the passenger side of the car, the #1 cylinder is the first one on the left. #2 is middle of the rear side and #3 is the far on (driver's side) on the rear bank. 4, 5, 6 go from passenger side to driver's side on the front bank.

The first part of adjusting is to see if the valve is already in spec. There are 2 intake and 2 exhaust valves for each cylinder. The intake valve bank is toward the center of the engine, where the intake plenum is, and the exhaust bank is toward the outside of the engine. Use a feeler gauge between the cam and the plate that is under it for each valve. The feeler gauge goes between the cam and the plate. Intake valves should be between .006 or .007 inches. Use the .006 and make sure it can fit in and should have very little resistance. Then, try the .007. It should also fit but it is ok to be fairly snug as long as the .006 can fit fairly easily.

While you are checking the valve clearances, you can also verify that the center rocker (the one that operates on the VTEC lobe of the camshaft) moves independently of the other two rockers. Just watch all three rockers while you press the feeler guage on the center one.

The exhaust valves are on the other side of the head and angled so you really can't see. But, they are symmetric with respect to the intakes. It is easy to feel around with the feeler gauge and to get it in between the cam and the plate. Contrary to the description in the manual, you will not need a mirror.

Exhaust valves should be .007 to .008 inches. If either of the blades of the feeler gauge fits in and is snug, then it is close enough. Also, you can see the feeler gauge coming from the back side up under the cam and towards you if you have the light just right. Check that the center rocker moves independently of the others, just as you did for the intake side.

If a valve is not in spec, then adjust it. I adjusted most of mine but this was partly because it was fun and partly for practice. Some were in spec and some were close. None were too tight. [Keith says: Mine were *all* too tight to allow the larger guage to be inserted at all, so I adjusted all 24.] Once you get this far, might as well make them as perfect as you can.

To adjust, put the screwdriver part of special tool in the socket part. Then, holding the top of the screwdriver a finger's width above the socket, put the socket over the hex nut on the valve. Then, fit the screwdriver into the slot in the screw head. Use use a 17mm wrench to loosen the socket. Try to keep the screw driver part of special tool from rotating. Once you have the nut loose (1/4 turn is enough) you can loosen or tighten the screwdriver part. Keep the socket and wrench on while you adjust. It only takes a small fraction of a turn of the screw to go a few thousandths. Once you have adjusted the screw, tighten the socket by hand, then more with the wrench. The torque spec is 14 ft lbs. Then, re-measure and re-adjust if necessary.

Once you have done all 6 cylinders, putting it back together is the reverse of the above. Make sure to check your rubber seals for cracks. Replace if necessary. Briefly, for both front and rear cylinder backs, the procedure is: put valve cover back on. Put 6 washer/seals back on. Put two center nuts back on center shafts and tighten. Put coil wire back in. Coil wire has loop that goes around center shaft and fits down around shoulder of center nut. You can do this by feel or use a hand mirror to make sure this is down all the way. Put coils back in. Put coil wires on. Put coil bolts on and tighten. Put brass-colored sleeves around center shafts.

After putting wire holders and plastic wire covers (front side) back on, put the non-shiny cap nuts on the valve covers. Put coil covers back on. Put bolts in coil covers. Put shiny cap nuts on the front coil cover, and non-shiny cap nuts on the rear coil cover. Tighten 6 cap nuts. Tighten 4 coil cover bolts. Connect wires. Re-connect hoses to head covers. Put wheel back on, lower, and torque lugs. Remove service mat.

All in all, it wasn't that hard. Now that I'm good at this, I can probably do the whole thing in 4 hours or less. [Keith: that sounds about right to me, too. Figure 5 to 6 hours the first time, if you have to adjust all the valves, much less later when you don't.]

[DNG] It's VERY straight forward.

  • Take of the coil covers, coil plugs, and coils.
  • Disconnect the O2 sensors.
  • Loosen 4 nuts at each corner.
  • There are two additional nuts in the middle of the valve cover. They are mounted on these 2 long bolts which are part of the cylinder head. Take these off and the cover lifts right up. You might need a flat screwdriver to get things started.

There are two gaskets per valve cover. One covering the cam timming sproket area and the other the rest of the valve cover. Take note which gasket overlaps the other one.

The rear valve cover is a little tricky to lift off because of the tight area. Once all the nuts have been removed, the trick is to turn the valve cover 90 degrees prior to removing.

>Do I need to replace the gaskets ?

It's recommended. Sorry I don't have the part #

>Do I need to buy any silicone or other adhesive ?

On the bottom of the valve cover, there's this plate which is held on my some 10+ 10mm bolts. Once removed,
the plate are sealed with Honda Bond. You'll need the Honda Bond to reseal the plate.

>Do I need to take the spark plugs out ?

No

> The coils off ?

Yes

It it possible to do this without the special wrench?

[AVI] I did mine with a 10mm deep socket (SEARS) and an allen key ground to a screwdriver tip at the long end. The socket was 3/8" drive and 2.5" long and allen key just long enough for the short end to clear the socket. Worked fine but you need to recheck the clearance after using a ratchet to tighten the nut.

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