Pre unit B series Cam Identification

[Vince31]

I have recently purchased a Goldyfied 410cc B31. I am interested in making it go better by fitting Gold Star cams. The trouble is I don't know what cams are in the bike. The only marks on the existing cams are a "D" on the inlet and a "V" on the exhaust cam.  I have searched the web and the BOC library but cannot find out how to identify the cams.
From my research it appears that 65-2446 cams are the ones to use but maybe somebody knows better.

Can anybody help please?

[Pete C]

I have a box of standard looking cams with a variety of markings, one even has a D on it. The inlet and exhaust cams are identical and you just use the dot or dash depending on inlet or exhaust.

The 65-2446 cams will be good but I would check that they do not cause the springs to go coil bound at max lift and that the spring collar doesn't contact the valve guide. I had to trim a bit off the top of the guides when I fitted higher lift cams to mine.

[Vince31]

Thanks for that Pete C.

Do the 65-2446 cams have any identification marks I wonder?  It is no good going to an autojumble or looking on fleebay if I can't tell what cams are being offered.

[Pete C]

Gold star cams will have the number stamped on them. There are a few suppliers of new cams (not cheap) if you are in the UK.

[Pete C]

Hi Vince
PM sent 
Pete

[Vince31]

Hi Pete C

Thank you for that detailed description of B31 tuning.  I recently bought my bike with the 410cc conversion but it wasn't running properly and the barrel/head joint was blowing. It also liked to kick back when I tried to start it.
I had the head and barrel off and confirmed that it had a 1.7mm plate under the cylinder. The piston had a small dome but I didn't measure the height or photograph it. After lapping the joint and re-assembling the engine it still didn't go properly but a new 27mm concentric with 260 main jet, no3 slide and the needle at its richest position now has the engine starting and running well.
I am more interested in pulling power rather than more revs and would rather stick a B33 top end on it than tune the smaller engine other than perhaps changing the cams.

[Derek996]

The standard cams (65-2420, inlet and exhaust) usually have no part numbers but may have  a letter on them that must have meant something to BSA. Gold Star cams always have a part number on them.
I run a B32 competition (same engine as the B31) with a 9:1 piston, a 65-2446 inlet cam (Scrambles inlet or exh. or Clubman's exh) and a 65-2450 exh (Tourer exh) Fortunately I had no issues with the springs. It is still on +20 with an excellent bore so I decided to keep it at that rather than bore to accept a T140 piston.
The attached charts will give you all the Gold Star cam information.
Gold Star cams are available from Newman Cams at around £130 each. http://www.newman-cams.com/wp-content/uploads/2022/12/BSA.pdf

[Vince31]

Hi Derek
Thank you for the cam info.  It is the first time I have seen any details of the cam lift.  My cams have 0.3" lift so they must be standard. 
I will trawl the internet for some cams. 
My engine is a 1954 BB31 in a 1954 swing-arm CB31 frame.
If anybody in the club has any 65-2446 or 65-2450 cams for sale please let me know.
Vince

[Rupert]

Nice to see so much info on these cams in one place, thanks for that.
Any idea if the equivalent data for the late 30's/wartime M and B series cams is available anywhere? I have a reference to cam 65-1182 used on both inlet and exhaust and would like to know how it compares with any of the post war cams.

[Derek996]

Sorry Rupert, I've only got the info for the post war pre-unit singles.

[Pete C]

Below is the advice I was given when I was deciding which cams to use.

I went with 2448 inlet and 2450 exhaust as these were what I found in a 25 quid crankcase I bought at Stafford 

You particularly need to check cam information when swapping cams into the 350 engine. (if you have fitted an oversize inlet valve).
You will note some cams are listed to be used with the '10 degree' timing pinion.
Although piston clearance has to be looked at when using a high lift cam the other thing to consider is 'valve to valve' clearance.
With large valves in the small 350 head there is a potential for them to tangle up around TDC...the 10 degree pinion alters the timing slightly to avoid this with particular cams.
If you have fitted a larger inlet valve this could be a factor.
When Gold Stars blow up (both 350 and 500) it is often the case that the valves have hit each other, not that one of them has contacted the piston.
65-2448 is the touring inlet cam is relatively mild and standard valve springs will be ok with this one and you won't need to shorten the top of the valve guide for clearance at maximum lift.
You are very likely to encounter problems if you fit anything 'hotter' to the 350, such as 65-2446, the scrambles cam. In that case further head, valve and guide modification will be required to avoid the problem.

[Vince31]

Thank you everybody for all the cam information. 
I am now looking for 2446 2450 and/or 2442 cams. 
I have found Newman Cams manufacture and sell cams and their prices are less than some of the tatty stuff on auctions sites.
I have screwed the timing cover back on now so I'm not in a hurry until the weather gets warmer.  I will use my bikes with screens and heated grips until then.

[Derek996]

I bought my cams from Newman. It took a while because 2 of the machines the use for grinding these cams were broken so they had to set up another one. If they have a machine set up for their grinding then I'm sure you will be fine. I notice that their prices have gone up a little since I bought them last year, not surprisingly really.