Toyota uses "lobular" studs and flang nuts to mount the oil filler neck to the valve cover.

It looks like crap.

So...

LS430 Cam pulley covers and plastic engine cover use acorn flange nuts...


LS43O (3UZ-FE) inatalled in my LS400. Studs are the way to go in this application, but Toyota should have dressed it up with acorn flange nuts.

For illustrative purposes, the OEM nut on right is used on plastic engine cover and the left is from cam pulley cover. The first can accommodate the stud length but it's rotating flange hangs over the filler flange, while the second is a better fit, and has a fixxed flange will require shortening stud.

Will select one type and paint to match.

 

Yes so now you can't get any sort of penetrating oil on the threads......and the contact is made further away from the center-line of the stud.

 

Sorry Yoda I don't see any benefit whatsoever, not even on an aesthetic level.
That coil pack bolt is GORGEOUS though!
To each his own...

 

Confucius say
When one is concerned about the aesthetics of oil cap bolts one might need to re-evaluate life priorities

 

Wasn't Confucious a Chinese philosopher??..yet this is a Japanese engineered and built Automobile...

Sorry, in view of global situation, at the moment not feeling charitable to China...

Design details and aesthetics is an attitude.


Polished 3UZ-FE cam cover(s)

Before and after (in process)

Mustn't forgot the valve covers..(in process)