Schedule (Maintenance)

[Tom239]

About http://www.nsxprime.com/wiki/Schedule_(Maintenance):

The wiki page recommends valve clearance inspection/adjustment
every 15,000 miles, which is consistent with the 1991 service manual.

Honda's recommendation for later model years (e.g., 1995; I don't
know when it started though) relaxed this to 30,000 miles.

Is there a consensus about whether 30,000 is an okay interval
for older cars as well? Any thoughts about how to best note on
the wiki page how the recommendation changed from year to year?

 

[Daedalus]

Since there is virtually no difference between a '91 and a '95 engine, I think a 30k interval would be fine. My '94's valves at 52k, never adjusted prior, were only .001-.002 beyond inspection range worst case. The '94 owner's manual shows a 15k mile interval, so '95 must have been the first year with the "official" extended schedule.

 

[HondaHeat]

Since there is virtually no difference between a '91 and a '95 engine, I think a 30k interval would be fine. My '94's valves at 52k, never adjusted prior, were only .001-.002 beyond inspection range worst case. The '94 owner's manual shows a 15k mile interval, so '95 must have been the first year with the "official" extended schedule.

This is incorrect information.
The heads on 95-96, the first "fly by wire" NSX's, are different from the 91-94.
The throttle body, of course, is different as well.

 

[Tom239]

This is incorrect information.
The heads on 95-96, the first "fly by wire" NSX's, are different from the 91-94.
The throttle body, of course, is different as well.

But do any of the changes associated with throttle-by-wire have a bearing on valve clearance?

1994 and 1995 have the same part numbers for valves, rocker arms, and many others.

 

[HondaHeat]

But do any of the changes associated with throttle-by-wire have a bearing on valve clearance?

According to the manuals the valve clearance specs are the same throughout NSX production, that is, both NA1 and NA2 motors, so the answer to this question is no.

You will notice some service intervals were more conservative in the first years of production. As time went by, and as the cars aged, Honda gathered more data and they have accordingly made adjustments to some of the intervals.

1994 and 1995 have the same part numbers for valves, rocker arms, and many others.

I'm sure that's true but as I stated before, the heads are different.
The bottom of the 95-96 motors are the same as the 91-94.

 

[Daedalus]

This is incorrect information.
The heads on 95-96, the first "fly by wire" NSX's, are different from the 91-94.
The throttle body, of course, is different as well.

Perhaps your definition of "virtually" differs from everyone else's. I could also argue that the throttle body is not actually part of the engine, as it was not a part of the "engine assembly" listed in the catalog. Regardless, the throttle body is immaterial to the question asked.

Second, if "fly by wire" [sic] engines are so radically different, why do the rear heads have the same part # for all '91-96? The front heads have identical internal parts (except for longer exhaust studs), which suggests only minor differences in the castings. But even the front heads have different part numbers between '91 and '94.

 

[HondaHeat]

Perhaps your definition of "virtually" differs from everyone else's. I could also argue that the throttle body is not actually part of the engine, as it was not a part of the "engine assembly" listed in the catalog. Regardless, the throttle body is immaterial to the question asked.

Second, if "fly by wire" [sic] engines are so radically different, why do the rear heads have the same part # for all '91-96? The front heads have identical internal parts (except for longer exhaust studs), which suggests only minor differences in the castings. But even the front heads have different part numbers between '91 and '94.

I would agree the throttle body is not actually part of the engine, didn't say it was, just that it also was different on the 95-96.
(so was the transmission )

Virtually:vir·tu·al·ly
Pronunciation: \ˈvər-chə-wə-lē, -chə-lē; ˈvərch-wə-lē\
Function: adverb
Date: 15th century
1 : almost entirely : nearly
Yes, the engines are nearly the same.
If it suits you to be "nearly" or "almost entirely" correct it's cool with me but it doesn't help when your trying to build a Wiki with good, solid information.

Now were getting off topic here but..

If you take a set of heads off a 1991-1994 and want to bolt them on a 1995-1996 or vice-versa, they will not work. Please, let's not go on forever here. Just ask someone like Shad, Mark Basch or LarryB, someone you believe, trust and who has been there and you'll find out it's true.

This would be good information in the WIKI as people may need to replace a set of
heads on a 1995 or 1996 and should know when shopping used parts what will and won't work.

The adjustment to the valve clearance would be the same.(Back to topic) and I agree. I think 30k is fine.

 

[Daedalus]

If you take a set of heads off a 1991-1994 and want to bolt them on a 1995-1996 or vice-versa, they will not work. Please, let's not go on forever here. Just ask someone like Shad, Mark Basch or LarryB, someone you believe, trust and who has been there and you'll find out it's true.

I will take anyone at their word if they say they've tried it. But I still think the rear heads at least have to be interchangeable since they have the same part number. Unless, of course, the parts database I'm looking at is incorrect. It happens.

 

[Larry Bastanza]

Front Head - 1991-92 12100-PR7-A00
Front Head - 1993-94 12100-PR7-A01
Front Head - 1995-96 12100-PR7-A02

Rear Head - 1991-96 12300-PR7-A02

Here is what is interesting. Originally the rear head also had an A00, and an A01, and was bumped to A02, AND A02 is compatible for 1991-96.

Edited Correction Below

In regard to the maintenance schedule, my OPINION, and nothing more then that, is that the changes are purely "marketing driven", due to pressure from the industry at that time for a "100K Major Service" interval. Typically engineering would sanction these changes.

HTH,
LarryB

 

[HondaHeat]

I just assumed that you had done this or attempted this head swap Larry that's why I mentioned your name.

It was Mark Basch that personally told me that it would not work when I wanted to do such a swap myself. He specifically told me that the head set (pair) had to be from a 1995-1996 to go on a 1995-1996, that they were different due to the "Fly By Wire".

I took it as gospel since he usually is spot on with this stuff.

 

[Larry Bastanza]

I took it as gospel since he usually is spot on with this stuff.

As you well should have!! Mark is correct, and in fact the numbers are different for a reason. Pbassjo and I were discussing this tonight and he too recalled the discussion with Mark, based on his 1995-96 engine. So the above part numbers are correct, and the parts catalog states there are three versions for the front andthey are not interchangable, but I do not really know the exact difference.

Now I question the difference between the 1991-92 and 1993-94 heads as well.

Regards,
LarryB