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Today at Atelier Kaz - Private NSX Enthusiast, ex-Honda R&D engineer with F1, Indy/CART background

Eng Refresh + LMA, Health Check, etc 27

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As keep cleaning the engine with one's head in similar position makes shoulder stiff, decided to change the rhythm of the activity.



The first package for the extra parts arrived so started replacing auxiliary components.

















New bearing for the a/c idle pulley.

You can see the partial crack on the pulley itself at the lower section of this photo.

Overlaid the new belt and the cracked section didn't touch any part of the belt so happy to re-use it.



















New rectifier. Apology for the poor focus....

Looking fresh and installed.

















As reported earlier, the rear header was hitting the sub-frame so decided to take a look at this stage.

And yes indeed. It was hitting for quite some time.


Considering the design/material/shape/etc, I don't have enough confidence in making big enough changes to the header side to
prevent it from scuffing the sub frame and obviously, you don't want trimming off the sub frame so
going to see how much changes the new front eng mount can make.



















By the way, the owner was still using the NA1 spec stud bolt, gasket and nut with the header.

I always recommend using the NA2 spec ones but these are something 'better' and not a MUST process.

The diameter of the NA2 gasket is just a bit larger (overlaid NA2 spec over the NA1 in the photo, about 1 - 2mm wider so less friction but
considering the exh gas speed, by how much???) and the nut has better treatment against the future corrosion.

The stud bolt is shorter so it won't heavily corrode all the way.

After discussing with the owner, we are going to replace the gasket and the nut to NA2 spec.
The stud bolt looked to be replaced in the past and all 14 of them are in very good condition so just going to leave them.









Comments

  1. greenberet's Avatar
    Dear Kaz,

    If you hold the NA1 gasket up against the NA1 cylinder head, do you feel a slight step between the two? Is the cross section of the NA1 gasket a bit smaller than the cross section of the NA1 exhaust port?
  2. Kaz-kzukNA1's Avatar
    Hi, greenberet.
    Yes, that's part of the reason why I spent long time before deciding on the aftermarket header selection.

    Even for NSX engine, it's just a production car and not race engine so the intake/exh ports are not polished.
    Also, the accuracy is not super high that you will even notice tiny difference in the geometry of the exh port between the front and rear cyl head when you overlay the exh gasket.
    Some heads are fine but others will show tiny amount of gasket sticking out over the exh port in one direction.

    This is also highlighted on the flange material/design/accuracy of the aftermarket header.
    Some of them showed not perfect alignment against the gasket that it will restrict the gas flow although as in my post above, not sure how much effect it will have when the exh gas speed is so high.

    Machining/welding thick SUS at the flange is not cheap/easy depending on the SUS material used.
    Thus, reduced accuracy.
    Some of the aftermarket header can move in several directions even after the flange was inserted over the 7 x stud bolt.

    On the other hand, the gasket has very little tolerance that unless you line it up perfectly against the 7 x stud bolt, you can't even place it flat.


    Kaz

    Updated 12-09-2017 at 11:06 AM by Kaz-kzukNA1 (extra info)
  3. greenberet's Avatar
    Dear Kaz,

    Thank you very much for the answer. I installed NA2 gaskets in my NA1 the last time my headers were off and didn't think they would help much. However, your explanation is very clear and now I'm glad I installed the NA2 gaskets after all. Thanks again for the answer and thank you for all your valuable contributions to the NSX community!