Head stud installation height
 

hello

I understand that the installation height of the head stud should be 135mm, but is it from the plane of the spigots or from the top of the stud hole?

Logic tells me it's from the plane of the spigots but the figure 3-34 on page 137 of wayne's book shows that a ruler is measuring from the top of the stud hole..

Please clarify.

You need to measure from the stud hole surface.

Cheers

The measurement is made from the top or machine edge on the cylinder spigot hole.

The reason you measure from that point is because stud length is a factor of cylinder length, head deck and spigot height.

The measurement should actually be changed based on machine work performed.
That is one good reason the run after market head studs.
With the best head studs, installation height is irrelevant.

Hi

As Henry says 135mm is the factory height but machining will shorten it, I did a test install at 133 (As I had skimmed heads and case spigots) and that worked fine, what you have to avoid is having the studs to long (as they will push the allen socket out of the nuts) or too short (where you don't get enough sthread on)

HTH

My Bentley clearly shows the height measured from the hole for the stud. I can't find it just yet in my factory manuals. I am open to the fact that the Bentley may have an error..... If you reface the spigot surface you would probably use a thicker shim to get your deckheight back. This would not require changing the height of the stud. Plus how much are we talking about taking off here? If you skimmed the heads, you *may* once again use a thicker gasket to regain deckheight or valve clearance or CR that was altered by skimming the head. Once again, this would not change the height requirement of the studs. Plus, a few of the motors I checked that had the factory studs had variances of +/- at least 1mm anyways!

You are right, with the factory studs and nuts you do not want the head stud to poke throught he barrel nut. But, like Henry said, if you use aftermarket studs that do not use a barrel nut, this is not a problem. Your only concern is making sure there is enough thread to get the correct torque. This could be a problem with studs like the ARP that I have as you may set them too high. But, it sounds like this is not a problem with the Supertec studs which I am thinking are probably a better product!

Cheers

131.5 mm from the seating surface of the cylinder.