Rocker Boxes

[Brian]

I have read somewhere but cant remember where that the way to tell the difference between a rocker box for a iron head and a alloy one is to look at the part number on the underside of the box. The iron head has the numbers cast in and the alloy head ones have the number stamped in. Can anyone confirm this or does anyone know of another way to tell them apart.
                                                                                     Brian.

[RichardL]

Since my engine is apart, I thought it would be interesting to take a look at this. I'm afraid it doesn't answer the question exactly. I have a '55 A10 with an alloy head. My rocker box has 67-260 cast into it. I think this corresponds to a plunger cast head model but my parts books says that would be a 67-259. Regardless. right on top of the 260 is stamped 1142. My parts book lists a 67-1141 for a Road Rocket. Needless to say, this leaves me more confused than before you asked the question. The cast in and stamped numbers on my rocker box both seem to be one version later than the numbers in my parts book.  I looked at two different ebay sales with 260 and 1142 and they are both saying these are for Rocket Gold Star (this could just be loosely stated). Babbling on, there is a possibility that my head and rocker box came from a later engine (Super Rocket or Rocket Gold Star), as it has been noted in this forum that the alloy head would be inconsistent with my engine number being absent an "R" after the "CA10".

OK, I'd better stop so others don't have so much to correct.

Richard

[bsa-bill]

Hi guys - are we remembering that cast numbers were usually one away from part numbers.
However all four of my rockerboxs have 67-280 cast in them, not much use as my spares book (later s/a models)gives the following numbers
42- 0136  A7s/s
42- 0137  A10as/r
42- 0138  A7/A10

a possible explanation might be that all boxes are cast the same and just machined differently, I recall something about the length of super Rocket valve or valve/springs require more clearance.

No doubt no need to warn you about Ebay descriptions, in particular RGS - usually means it might fit a RGS

All the best - Bill

[RichardL]

Gents,

A small detail I forgot to consider, my spares book is for '54 to '57 bikes, which explains much of my ignorance. However, Bill, I wonder if the "8" in "280" could not actually be a "6". On my own rocker box, said number is almost impossible to read under the number stamped over it. A very good photo I have of the backside of a part on ebay looks more like a "6" than and "8". Then, going to the online stores, 67-0280 is listed as a rocker box stud. Apologies for getting too much info from the web, versus experience with multiple bikes (does taking the same one apart repeatedly count the same as having more than one?), but one of the online distributors in question is SRM, so I am fairly confident in the information.

All this being said, I don't think I've contributed much to the question of stamped numbers versus cast numbers. I know that valves and springs changed between '54 and '57, so it makes sense that machining of the rocker box may have as well. I think it also makes sense that in the earliest models there was no need to stamp over the cast-in number. The question is, if Brian is looking for rocker box, and it only has 67-259 or 260 cast in it, with no over-stamping, can he assume it will fit a later model? Without more detail and, maybe, a direct comparison with a known correct part, and based on my limited experience, my answer to that question would be, "no, he cannot assume."

Richard

[trevinoz]

You will find the rocker boxes are listed as "rocker box with studs". Different heads have different studs, therefore a different part no. for rocker box. I have seen written somewhere that Rocket boxes are machined differently for the valve spring clearance but

[trevinoz]

The parts book shows "rocker box with studs". Different heads use different studs therefore different part number. I have heard that Rocket boxes were machined differently to clear the valve springs but I have had no problems fitting iron head types to alloy heads, I just change the studs.
Trev.

[G/F DAVE]

I have had rocker boxes with half cast/half stamped part no .These are for alloy heads with the big valve springs ie rgs & super rocket,  BSA also used this type of markings on big valve rgs & super rocket cylinder heads. Although I could not see the difference between these and other rocker boxes I have apart from longer studs as per alloy head. Dave......