This is a replacement Rocker Ball pin, to fit the front (pushrod side) rocker on 1938-1947 type OHV engines. The profile is copied from an original pattern and the ball and shaft are hardened.
Price is Each (i.e. 2 are required per engine)
As can be seen, these 'pushrod side' rocker ball ends were pressed into the front rocker arms on the 1938-1947 type OHV engines. The ball end of these rocker ball pins fits into the corresponding pushrod top cup. It is not unusual on this particular type of rocker box to find the original pin is badly corroded, or just has worn through the case hardening of the ball.
These rocker arm Ball Pads are copied directly from a 1939 rocker pad - taken from the rockers in the accompanyning photos. The profile of this item exactly follows the original - which is quite important, as the side wall profile is also important so as not to fould the pushrod cup on full deflection.
These are CNC manuactured, then are case hardened, in EN32B.
Please Note: wtih 'Press In' Rocker pads - it is very difficult to gauge the correct 'interference fit' into the rocker arm - as tolerances between original items can vary by 1 - 2 thousandths of an inch on originals - particularly those that may have been removed from well used engines, as these can sometimes have slight wear in the rockers. We have emulated what we believe to be the normal 'interference' fit for these rockers in a good original Norton rocker arm. The old rocker pins can be removed from the rocker arm using a studded punch - as per the one in this photo - which has a 'pip' in the centre of the punch that corresponds to a centre hole in this type of rocker pin. We have found most originals have a slight taper at the start of the shaft - that makes it slightly easier to press them in - as that allows the pin shaft to 'just start' in the hole, before it needs fully pressing in.
If fitting one of our rocker pins to replace an original - you should find that the new pin 'just enters' the hole, but requires light pressing in to fully press it home. If the new pin slides all the way in on its own, or only goes firm in the last 1/4" of the shaft length - then it is likely that the hole of your rocker arm has a looser tolerance than required. It is the customers responsibility to satisfy themselves that the new item has sufficient interference fit for their own engine
We do have a few pads with either looser or tighter interfence fit than what we consider to be the 'standard fit', if you are not sure you can email us on sales@racingvincent.co.uk for details or availablity.
Final point on this 'ball type' or rocker pin. These are specifically listed in the 1939 Spare Parts List as Part Number 8908. The earlier 1932-1937 type OHV engines also had rocker balls on the rocker arms - but the rocker ball pad is not listed as a seperate part on those earlier engine types, and I do not have an original pattern in our 'originals' collection - however, it may be that the earlier engine also used a seperate press in ball pad on some models of a similar design . . . again, if you think this type may fit your earlier engine, you can email us for details.
And finally - these ball pads look very similar to the type also used in 1948-57 type OHV engines - but actually, the design of that later ball is slightly different to these balls - the later design also has a side oilway on the shaft that came out at the centre of the ball - to provide an additional oil feed. As of Oct 22: We may be making that later type in the future if required, but will gauge interest first - email us if you need one of the later type
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