Exhaust Stud Bolts (1994) - Need Part Number Confirmation

[mwagner10702]

Can I get confirmation this part number is the exhaust stud bolt = 90020-PH1-000 (1994). I want to order some ahead of my header installation.

Thanks in advance.

Mark

 

[chudson1549]

I believe that's right

 

[Larry Bastanza]

I think it is this: 90021-P0G-A00

Look in the parts catalog under "cylinder head"

HTH,
LarryB

 

[mwagner10702]

Looking at the parts catalog that I downloaded via the Wiki (http://www.nsxe-repair.com/files/acuraparts.zip) I found two different part numbers for different years, see below. Appears the differences are length; 43mm (1991 - 1994), 41mm (1995 - 1996). Not sure why the change since the actual exhaust manifold didn't change until 1997. In any event it looks like 90020-PH1-000 is the correct part for my 1994.



Thank you Larry for the parts catalog suggestion.

 

[Kaz-kzukNA1]

I believe you are referring to the stud bolt at the exh port on the cyl head.

If installing header on NA1 engine and unless the header is using extremely thick flange for some reason, then I recommend replacing all stud bolts to the NA2 spec, 90026-PV0-000.

It's shorter and has better chance of surviving against corrosion/rust over years as the threaded section is protected by the nut.
If you look at your existing 91-94 spec stud bolt, you will understand it especially if they are all rusted.
The longer exposed thread section would be very rusty and some cases, you would take out the stud while loosening the nut (not a problem).

Even the 95+ NA1 spec stud (-P0G-) is bit shorter than the 91-94 one but again, unless the header flange is massively thick, go for the NA2 -PV0- one.

At the same time, for the same reason, I recommend replacing all the nuts to NA2 spec 90217-657-000.
Unlike the split design of NA1 nut, this one has better treatment and will survive longer against corrosion.

Ideally, you should replace the metal gasket between the header and the cyl head and if doing so, again, please select the NA2 spec 18115-PBY-J02.

The exh port size and the geometry on the cyl head as well as on your header are not accurate and not consistent.
You won't be able to see it but quite often, the geometry of the header port opening doesn't necessarily line up properly against the exh port on the cyl head.
It's a tiny difference but NA2 gasket has slightly larger hole size than the NA1 one so you may gain just a tiny bit of non-disturbed extra flow.
In the above photo, overlayed NA2 gasket over the NA1 one and you can see the tiny difference in the hole size.

Good luck.


Kaz

 

[mwagner10702]

Thank you Kaz for the recommendations. I will check the flange thickness on the headers to determine if I can use the studs you suggested. I will order up (14) nuts (90217-657-000) per your recommendation. The headers come with cyl head to header gaskets so I will check the port size against an existing set of NA1 gaskets I have on hand. If the port size is the same I'll order up a set of NA2 gaskets (18115-PBY-J02).

Fortunately (future) corrosion is something I don't need to worry too much about. I am one of those "crazy" owners who only drives their car on dry days and I probably put only a 1000 - 1500 miles a year on it. Not to despair as I accumulate these miles on the race track (HPDE) and summer driving events (tours, road rally events, etc) so the car gets used as it was intended to be used.

 

[Larry Bastanza]

Kaz,

Thanks for your comments. Funny I happened to look up the 1995, since I was looking for another part, and thought to myself, same manifold, 1991-96 so that should be the same stud. Proably will never know why they are different....

Regards,
LarryB