Good point. The early A12 kit (ARP 202-4202) does contain one smaller-diameter bolt

but the A14/A15/late A12 kit does not appear to (ARP 202-4203). It looks like all the bolts may are thinner than the early A12 kit?

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  ARP 202-4202.jpg (21.00 KB)


  ARP 202-4203.jpg (51.35 KB)

ive used ARP head studs in my a12 (early engine) and my kit came with 1 head stud of smaller diameter

they may have packaged up your stud kit incorrectly? I would check with your supplier

On the other hand, Datsun engineering thought it was important enough?

* Center bolt: 8 mm diameter
* other bolts: 9 mm

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  Head Bolt thickness 24733.jpg (20.88 KB)


  center bolt A14 23623.jpg (52.07 KB)


  1973_head_bolt.jpg (55.17 KB)

My thoughts:

1) the oil is only used to lubricate the rocker arms and pushrods tips

2) i haven't heard any complaints from those who have used the ARP kits

ARP stud kit #202-4202 is for early engine (all studs same length)

ARP #202-4203 is for late engines (with one long stud)


The engine blocks differ in the oil passages. Either way, the oil goes around the head bolt in the head to the rocker shaft pedestals

For my A15 I'm using ARP head studs this time. What I noticed right away is the stud for the oil hole is the same diameter as the others whereas with the standard head bolts that particular bolt is thinner.

So will this matter? There is still a gap that around the stud that oil would flow through but is that enough?

The other thing I could do is drill out the block to so the oil passage lines up with the hole that is in the GX head.

Thoughts?