Alloy heads

[Brian]

Came across this site, assuming the info in it is correct it helps identify the different alloy heads.

http://atlanticgreen.com/a10alloyhead.htm

[trevinoz]

He missed the 67-1571 which was fitted to the last Rockets.
The number "71" was over stamped on the "49" which was ground out.
Trev.

[Brian]

There's one of those on evil bay at the moment.

http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&item=250548216277&ssPageName=STRK:MEWAX:IT

[trevinoz]

I had a look at the head. It is a myth that these heads were exclusively RGS. After all, the RGS engine is just a standard Super Rocket engine.
I may be taken to task over that statement, but I stand by it.
The RGS engine came with 8.75:1 pistons and 357 cam but so did a lot of Super Rockets. Some even came with 10.5:1 pistons. Buyers choice.
The Huntmaster rocker box is a bit different. I have got two of them on the shelf but no Huntmaster.
Trev.

[Joolstacho]

My SR engine was bought from a guy in Kent who told me it had been used for Grass Track racing (and from the valve damage I later found I don't doubt it!) -All fixed now, but I suspect he might have run it on alcohol, and I'd like to check head dimension to see if it has been skimmed. My head measures 21.5mm from bottom (cylinder) face to one of the headbolt inner 'lands'.
My head is stamped 67-1547 1 (not on the AltanticGreen site), valve sizes are IN 1.45"  EXH 1.38"
Interestingly the engine number is A10 5851 - no model prefix, so I assume that they are replacement cases.

Cheers,
Jools

[rocket man]

your right jools a lot of super rockets sent a con-rod throe the case mine did as-well
when my engine was rebuilt by srm engineering they said  it was a good match because everything lined up
without eny  probs  a10 and super rocket cases where the same also have the 375 cam in mine

[trevinoz]

Jools,
              You will probably have a 42-1571 head.
trev.

[chaterlea25]

Hi Jools,
I have just measured the 1549 head that I have bought to replace the A7 head fitted to the SR I am working on
This head was a real find as it is completely unmolested, I dont think it was ever removed from the engine until now!!
I got it from USA!
Depth of front outer bolt holes 60 mm
Depth of inner rear bolt holes 52.7mm
Measurement from rockerbox face to head gasket face 70.5mm

On the 1571 heads the number was changed by BSA from 1549 to 1571 by grinding off the 49 and stamping 71 in its place.
This was done to diffentiate the "Big Valve" heads which have 1.5in inlet valves (and sometimes but not always the
1 and 3/16 dia. carb diamater) **These are my own observations from the different heads I have here in the workshop**
To confuse this a little more I have two 1549 heads one having a 1 and 3/16 inlet  and the head that came from USA has a 1 and 1/8 inlet,
The larger inlet does not look to have been done by "an amateur" so the jury is out on that one!!!

HTH
John O R

[Joolstacho]

That's really useful info John, -Ta.
On my 67 1547 1 head, the 67 154 is cast, and the 7 1 is stamped, Inlet valve is 1.450 so appears not to be a 'big valve' (although if seats and valves had been previously changed I guess it's possible). Inlet port is 1 3/16".

-Jools