A10 Big Valves - Rare?

[dwoodliffe]

I have started restoring a 1962 BSA Super Rocket (North American model) and this is my first post.   The head accommodates the big intake valves (1.5”) and I cannot find a reference to these in my parts book and this resulted in an incorrect valve order.  I believe the code number is 67-0691.  Are these big valve heads rare?  The only place I can find replacement big valves is on SRM. 

Cheers, Doug

[bsa- bill]

Hi Doug
Draganfly do them and I believe C&D Autos also.
There twice the price of standard ones though (lot more money for an extra 40 thou) £26....

I have two going spare, I had forgotten that I ordered these when I had a big valve head (later sold), consequently I fitted them to a standard head and one of them kissed the piston, could find no damage to the piston or valve but don't know if a bent valve is that easy to detect.

Anyway you probably want new

To be honest I don't think you would notice much in the way of benefit over standard valves unless your going racing, shouldn't think there would be much of a problem using standard valves in it, however wiser heads will comment

[muskrat]

G'day Doug, welcome to the forum.
                                               The # for the 1.5" valve is 67-0961. Big valve SR heads are like rocking horse poo.
Bill make that 90 thou, and if seat and port are matched I would be supprised if it didn't give at least 1 bhp more.
Cheers

[trevinoz]

All 650 alloy heads from 1960 are "big valve" heads!
The 1.5" valve was not standard and is an over size valve.

 Trev.

[dwoodliffe]

Thank you for the help.  I have had a steep learning curve learning about Brit bikes after working with a 1974 KZ400.  

I guess the called big valves are poor value considering the cost and must have been more of a marketing ploy.  Can anyone confirm that the smaller valves will fit on the big valve head?  I believe the part number for the head is 67-1549.  

This is the valve set I have:

http://cgi.ebay.ca/BSA-A7-A10-VALVES-AND-GUIDE-SET-/390326849290?pt=UK_Motorcycle_Parts&hash=item5ae14b0f0a

Cheers,


Doug

[trevinoz]

Hi Doug,
                 The part number you quoted is the casting number. The part number is 67-1548.
What is the head diameter of the inlet valves?
Do they fit the seats?
When you fit the new guides, you will have to have the seats re-cut.
Do you realise that the set you have bought, if they are as pictured, are not Rocket valves but are Flash or Shooting Star?

  Trev.

[dwoodliffe]

I gathered that and have contacted the vendor and plan to send them back.  I am waiting for my valve spring compressor to arrive and will evaluate them at that time.  I am actually hoping to salvage the existing valves.  There is some surface rust on the valve faces but it should come off.  A rough measurement of the intake valves and it appears that they are 1.5" in diameter.  I jumped in ordering parts without enough homework on the Super Rocket.  Part ordering was much easier with my KZ400!

[trevinoz]

Someone will give you the original size, it has slipped away at the moment!
Around 1.440", I think.
  Trev.

[bsa- bill]

Beg to differ Musky
This from the Atlantic Green site

67-1549
This head is for the 1960/63 Super Rocket & 1962/63  Rocket Gold Star.  No visual difference from the 67-1126 head was detected.
The valves for 1960 and up Super Rocket were intake #67-1551 1.455" (37mm?), exhaust #67-967 1.38"(35mm?)
The inlet valve for the Big Valve Super Rocket and Rocket Gold Star was #67-961 @ 1.5"(oh wow).

They also state the ordinary Alloy head can be used with the bigger valves - not in my case

[muskrat]

Sorry Bill  I was thinking of the 1.41" valves for '58-'59. My mistake. Sitting in corner with pointy hat.
Cheers

[bsa- bill]

Ah no worries Musky I just noticed that difference too, I got the 40 thou from measuring the big valve inlet with what I got from C&D to replace them, I could still have for the year wrong valves in there.
It's coming together nicely though

[muskrat]

Don't think they make valves big enough for this one http://www.ebay.com.au/itm/BSA-Alloy-Head-A10-Special-/110724597845?pt=AU_Motorcycle_Parts_Accessories&hash=item19c7b34855
    
Cheers

[iansoady]

Sometimes you just have to wonder.....

[bsa- bill]

Ah yes, the long lost development head, somewhere between A65 and rocket three

[chaterlea25]

Hi All,
Musky, Wasnt this the head that was for sale from the USA a few weeks ago 
Isnt the seller a member here??

To the best of my knowledge and practical experience with A10's
The 67-1549 head is fitted with the 1.450in. dia inlet valves,
The ""Big Valve" head with the 1.50.in valves is overstamped on the last two digits to make it 67-1571

When I built my SR engine, I was given (those were the days ) a 67-1571 head,
It needed a lot of work doing to it, I had it sorted by the "cylinder head shop"
I fitted it with their "Nucleus" valves which are modern "penny on a stick" design, these are 1.450 in.dia
as new seats were fitted. Their view was that the modern design would flow more than the bigger valves would anyway
Anyway the result is that it will rev out on the highest gearing that I can fit

Cheers
John O R

[trevinoz]

My two-bob's worth.

              There is a lot of confusion as to what was originally fitted to the "big valve" heads.
I have both, 67-1549 & 67-1571.
The inlets are the same size, 1.455".
I asume that the difference in the heads is the inlet tract as some export machines were fitted with an 1-3/16" carby.
I have attached a page from the factory tuning notes which states that the inlet valves are increased in diameter [1.455"] by fitting valve 67-961 which is listed in some publications as a Super Rocket, '58-'59, 1/16" os, making it 1.5".
I am again assuming that the author means to increase the inlet valve from 1.455" to 1.5".
I think that the Atlantic Green site is wrong in stating that the RGS & Big Valve were fitted with the over size valves as I have never seen a parts book which would back it. Nor the heads in my possession.
Logic tells us that BSA would give a head, with different size valves to standard, a new part number.
My parts book only lists the 67-1551 valve and the book includes all markets machines.       

   Trev.       

[Rocket Racer]

If the valve seats have enough meat on them to cope with the std 1.455 inlet big valve I'd be using that.
I fitted large valves to my earlier '55 head, supplied by draganfly and am now having to fit smaller valve seats on the exhaust so I can go back down on the zorst valve diameter. I didnt have valve to head issues with 8:1 pistons but was getting valve clipping.
My racing oracles opine that the big A10 zorst valves are too big in relation to the larger inlets.
I'm running with a 357 cam and looking forward to better reliability with a smaller exhaust valve.
That triple port head is just sad.

[chaterlea25]

Hi Trevor,
You maybe correct surmising that different size inlets were used for different "export" markets
I compared two 67-1549 heads and one has a 1 3/16 inlet port 30mm) and the other 1 1/8 (28mm) or so
Both did not look as if they had been worked on by "home tuners
The 67-1571 on my SR has a 1 3/16 port and had 1.5in valves fitted when I first got it??

All this tells us is that more or less "anything goes" when waffling on about these heads

Cheers
John O R

[jfligg]

Hi Guys
  My 1959 Brocher advertises a big valve head.  I'll let you guys know when I get it apart.  Jeff