Martensitic "stainless" is in fact carbon/chrome steel like some types I posted above. They have same expansion like silver steel etc. , but we were looking for something with higher expansion factors. For getting an idea I did a quick calculation:
Pushrod length 150 mm roughly, working temperature my guess 100 degrees ?
So this gives 0.20 mm expansion at ss factor 16, not 18 as with brass.
The cylinder plus head is alu, working temperature maybe 150 degrees ?? So expansion is 0.47 mm, so when setting nil cold you get extra valve clearance of 0.27 mm when hot - and you cannot do anything about it when stuck with ss. Even standard carbon steel is only 0.05 mm less expansion, so no big plus for stainless at all.
Unfortunately the common cams in Vincents never got effective quieting ramps for taking care of some more valve clearance and obviously drivers seem to be allright with the typical rattly timing side. And when you see that you cannot avoid 0.25 mm clearance in hot engine , in consequence the minimal quieting ramps don´t get much use at all - clatter.
For better matching heat growth of cylinder and pushrods you want alu but I don´t see a safe mod with original sizes like the solid steel types. Sooo, Vincenteers , look over your confined box and bin your belief that pushrods HAVE to be fed through rocker threads - isn´t so. When you manage to see more clearly you´ll find a lot more options for absolutely safe and durable mods like I posted in my photos : Alu tubes 10x2 mm plus hardened ball ends , for the pessimists get 10x1 mm stainless tube plus end caps. But no reduction of clatter with ss then. Yes, 10 mm will have not much clearance in the shroud at the lower end as there is a 1 mm faulty counterbore offset to match the follower cup. Either rectify this offset with suitable offset o-ring adapter to shift the shrouds to where they should have been from the start. Or fabricate longer end caps for the follower end of pushrod with smaller diameter. In the photo below the 3rd from left is a BMW /5 type with reduced diameter pressed into alu tube, no shifting needed then -would be only second choice for me.
Texts from old motor magazines about the super stainless steel in pushrods are just journalists talk, with no technical proof : The e-modulus (Young modulus??) is roughly same for all steel types and alu is one third of steel. That is why alu tubes want 2mm wall thickness to fight bending loads. Still my alu tubes plus steel ends are 10 grams less than standard - and come with about the same heat expansion - no better choices I can see so far.
I see another flaw with pushrod ends being same both ends- means that sitting in the follower cup gets decent oil collected, not so when the ball on the rocker side points UP into the adjuster cup. Pushrods no. 1 and 2 from left are alu Horex, upper end with the cup in the adjuster so all is well here ! I would not want to run "work hardening" stainless in poorly lubed high load applications. I have not come across that type of pushrods supposedly made from ss , my scrap rods are all very rusty so the ball ends will have been torch hardened I believe. Believe - I am not very religious , even less so with religions circulating in lots of different matters, technical or not. I want facts instead that can be checked and verified by scientific ways,not hearsay.
Vic
