Making new tappet adjusters.

Andrew I think you have your wires crossed, the spanner size is 7/16 which makes the thread 1/4

Well you live and learn! I have had just about every A series engine except for the 803! These all had 7/16" UNF tappet adjusters!

Thanks for that Bernard, I should have more success looking for those..

Andrew.

Hello Bernard,

The tappet adjusters on the Petter are 1/4" UNF, checked with measuring the diameter of the adjuster and a thread gauge.

For the A series tappet, I inadvertently typed 7/16". It should be 5/16" UNF !!!!!! Thanks for correction. The adjusting nut is 7/16" across flats and the very later A series had 1/2" across the flats, adjusting nut.

Thanks,

Andrew.

Edited By Andrew Tinsley on 20/02/2023 21:30:33

The tappet adjuster screws, and threads in the rockers, on the 803 cc A Series were 1/8 BSP from memory

1/8 BSP ,is 28 tpi, same pitch as /4 UNF, but different tread form. 

Indeed that is where I inherited the drill and tap from my father., or was he wrong?

Howard

Edited By Howard Lewis on 21/02/2023 15:17:49

Edited By Howard Lewis on 21/02/2023 15:18:25

I rather doubt they would be BSP as that is 0.383 diameter, just a touch over 3/8”. 1/4” BSF is 26tpi and quite likely was used before the motor industry moved to UNF and UNC.

Mike

Definitely 28 tpi, so probably Dad was wrong and they would be 1/4 UNF like the Unified threads use elsewhere in the engine.

Howard