Rocker nut thread?

[IslipMinor]

Phil,

I don't think it is actually a 9/32" BSC thread.

BSC has 60° thread angle, the same as the Unified series, so I would expect a production nut, or bolt, with 9/32" x 26 tpi to accept both UNS and BSC taps/dies.

I think it is more likely to be a 9/32" x 26 tpi UNS, i.e. a 'Special', so not listed as such and created for a specific purpose. The same applies to the crankshaft pulley bolt and the camshaft nut - they are both Unified thread form, but with a non-standard tpi, and so 'Special'.

How can we get a definitive answer to this?

On the rod bolt topic, we have Cooper 'S' rods in our 1380 and they are fitted with ARP 11/32" bolts! ARP part number 206-6002.

[philthehill]

Richard
Many thanks for your comments re rocker adjuster threads.
Whilst the adjusters (Pt No: 12A1215) and nuts (Pt No: 6K654) are available ex stock I agree it would be nice to know the precise thread of the adjuster.
I have after a very extensive search including enquiring at major tap and die suppliers been unable to find a comparable thread/tap to that used for the adjuster other than the cycle thread - so how to go about getting a 9/32" UN Special(?) tap to clean up the threads in pressed steel rockers is beyond me! The 9/32" cycle thread tap cleans up the female threads in the rocker nicely removing the crud without removing metal and that is all I want - therefore the 9/32" cycle thread tap is adequate for my needs as I am not intending to cut new threads. Thankfully I have plenty of used adjusters and locking nuts in good condition for both 9/32" & 5/16" sizes.

http://www.minispares.com/product/Class ... e/Cylinder heads/12A1215.aspx|Back to#mwp

http://arpinstructions.com/instructions/206-6002.pdf
Phil

[bmcecosse]

Rockers and adjusters are so plentiful - I would even consider cleaning up a thread - throw it away and use another if there is the slightest doubt about a nut having stripped on the thread.

[philthehill]

Pressed steel rockers in good condition are not plentiful and are no longer available new from trade unlike the later sintered rockers.
Pressed steel rockers and early steel rocker shaft support pillars can be easily machined to allow alignment of the rocker central over the valve stem unlike the sintered rocker and sintered pillar.
There is a ready market for pressed steel rockers in good condition at even what I consider to be high prices.
I agree that stripped threads on the adjuster and in the nut are a no no as regards reuse but I have yet to come across a damaged thread in the pressed steel rocker but those threads do get full of crud that can make it difficult to move the adjuster - so being able to clean the rocker threads is a bonus.
Phil

[bmcecosse]

I recently sold I think 5 sets of perfectly good pressed steel rockers - for very little money. No more left now - but a box of sintered ones -with adjusters and nuts - or maybe they already got binned - I haven't seen them for a while....