Valve Adjustment

[NSXBill2]

I searched and the DIY in the Prime FAQ says:

"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. ......

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."

Does everyone agree with this? What if I can get the .006 in easily but not the .007 on the intake. Why is it ok to have either of the settings OK for the exhaust, but you must make sure both of the gages go in on the intake?

The Manual just states the two ranges and says that they should show some resistance - doesn't say the high or low, or either, or both should show some resistance.

For the intake, I'm thinking if either .006 or .007 goes in at all and .008 won't go in at all, I'm good. This is not what the old DIY in the FAQ on Prime says.

Bill

 

[MJK]

For the intake, I'm thinking if either .006 or .007 goes in at all and .008 won't go in at all, I'm good.

That is how I did it.

Intake:.006(smooth fit) .007(very tight fit) .008(won't fit)
Exhaust: same, but add .001 to each

 

[NSXBill2]

That is how I did it.

Intake:.006(smooth fit) .007(very tight fit) .008(won't fit)
Exhaust: same, but add .001 to each

Thanks for the response.

Yeah, but what I'm asking is, what if (for the intake) .007 doesn't fit at all, but .006 does?

Bill

 

[MJK]

You're probably OK, but I re-adjusted mine when that condition came up.

Most of mine were out (>75%) and all that were out were too loose. I went with the theory that they were intended to be set as I described above and would loosen during engine operation until the next adjustment. Hence I figured a little loose would not hurt anything. I don't know what a little too tight would do. Probably nothing, especially if the .006 fits. But, I did not chance it under the rationale above. That doesn't make it correct, but on the bright side nothing has broken yet and that has been quite a while ago now.

 

[Daedalus]

I think all of mine were out of spec, but only by .001 or so. Since they were all loose, I aimed for the minimum of the tolerance range, the logic being they should stay in spec longer. I.e., .006 gauge would pass on the intakes with a good amount of drag, and .007 would not.

 

[NSXBill2]

OK so 1 to1 on answers :biggrin:

Anyone else?

 

[drew]

What if I can get the .006 in easily but not the .007 on the intake. Why is it ok to have either of the settings OK for the exhaust, but you must make sure both of the gages go in on the intake?

If the clearance is too small, then the valve never seats long enough to dissipate heat, knock out debris and/or close properly. Either one will burn through the valve, the seat or both rather quick.

It is much better to have more clearance than less. Make sure the .007 goes through or you are asking for real problems.

Drew

IMHO, it is darn there a waste of time to do the valves on the NSX. Extremely rare to be out of spec and over time the clearance increases anyways.

 

[NSXBill2]

That is how I did it.

Intake:.006(smooth fit) .007(very tight fit) .008(won't fit)
Exhaust: same, but add .001 to each

OK, I followed this from MJK (quote above). Worked well. One cylinder was good as is, one needed all 4 valves adjusted. The other four were varied in between. There was no pattern as to how they were off...some tight, some loose...never more than .001.

Tips: get a good set of feeler gages .006-.009, you need one of each. At first, I got some go/no-go gages that had a machined step in them (i.e. one gage had a .006 thickness and then a step to .008). I thought these would save effort, but the thinner area had machining marks that made it not smooth for measuring the "very tight fit" clearance. So I bought some regular gages:smile: . I actually had a standard set of "ignition gages" before I started this, but they didn't go down to the thicknesses required, so don't assume the ones that came in your Sears auto tool starter kit will work. I removed all the gages except for the four I needed from the set and reassembled it so I would have all four hooked together. This worked well. You get good at it after screwing around with the first one:smile:.

As I rotated to each cylinder, I would visually check all the cam lobes (use a mirror for the exhausts), so afterwards, I had seem most of all the area of all the lobes. Not sure what I was looking for...maybe unusual scoring or wear, chips or pits.

Also remember to check that there is freeplay in each center rocker (intake and exhaust) as you go to each cylinder (see the manual).

Besides the Honda valve adjust tools and feeler gages, you will need a torque wrench with a 17mm crows foot (kinda like the "C" end of a wrench with a square drive made to be put on the end of a ratchet. The crows foot allows the torque wrench to be used on the exhaust because they are so close to the firewall. I had a micro torque wrench (little over a foot long) and it was close-quarters doing the rear head, so not sure how a normal, full sized torque wrench would work there.

Hope this helps someone doing a search.

Bill

 

[MJK]

FYI for anyone planning on doing this, I bought a lot of the tools required on the cheap from amazon.

I used this great neck feeler $3.10, this telescoping mirror for $6.25 and this alltrade 648822 valve adjustment tool for $11.99. Add them all together and you get free shipping and no tax.

 

[Paul]

Here is another good reference for anyone doing this as a DIY.

http://www.danoland.com/nsxgarage/