A65 head modifications

Been perusing the BB boards on later vs early A65 heads and some of the (extreme) porting work being done. Reading Mr Pete's (RIP) advice, it seems that aside from seriously filling the intake bowl and raising the floors, a decent combination may be 28-29 mm intake tracts with the large valve set up of my 70 head. I have some alu tubing I could use to sleeve them. However, pinging Ed V (Michigan) his advice was to leave the 30mm intakes as is, open up bowls around guides, and run 32mm carbs instead.

Looking from some insight from knowledgeable folks here.

a gas flowed BSa ( 750 Trilple ) head here . P 78 picture of intake port .

( also youll see his first exhaust was a woftam , look n figure why , visualise collector flow ) .
Though normally youd ' Vee ' & streamline the guide support , and machine tapered Not shorten the guide .

f 750 NORTON ran 33 mm bore concentrics , so the 32 Id consider a minimum .

the KEEP IT SIMPLE , ' clean up ' - and NO recession on the seats , count for a lot .
You can mess things up tightening the bottom corner , so dont mess it up there .

besides the horribleness , the Recessed ' relieved ' ports IN the CHAMBER are horrible .



Nuther one ruined on the righthand valve - ' relieved ' mass lost flow . VALVE should almost be proud - In Chamber .
Any recession is lost lift . BEST is new hardened seats & no operations on chamber utside the seat whatsoever - -- -
Icrementally off seat , theres unimpeded flowing - not detours .



you can see some wallys ' cleaned up the head ( chamber )

as the valve seats about 1/8 recessed from stock . Oh Dear .



anutha ferkerp .


At Last , you can see the seats still level with the un recessed chamber -
so the flows unobstructed from the get go , lift wise .


Also slight ' flareing ' TULIPING after bend tru to seat - velly good .
tho Guides Unsupported .

Get AHEAD , 1 3/16 ths on a 500 .


nuther one where some ibaciles removed the GUIDE SUPPORT.


ROIT , you can see the ' V ' slitter type ' flowed ' support to the GUIDE . Also this;ll straightn you out , if your wondering . Bouta 1 1/8 port tunnels right on , for a 650 triumph .
Only the pre unit 8 studs unkinked from the head bolts , so flows bettern a 9 stud .

Now , If Hele had worked for B.S.a. . . . .

Look at the foist pitcher ( link ) and laste , moit .

Of Course , it'd Depend ,
if it was a road bike for pottering around , thatd never go above 70 . a road / race bike ( S / C ) Dirt Track , L S R . or a show bike that never runs .
The Budget .
and R.P.M.'s .
of course .
Also those there daytona heads might contradict a thing or two ive said , which proves one thing leads to another , and ya never know unless ya try it .
Tho a educated assumption after a considered evaluation should be maybe within the ballpark . Unless youre trying to break new ground .



Somebody HERE mentions Boring Ports to 32 m.m. which sounds a bit Chis Vincentish , so might be right if you want it to GO .

https://www.bsaownersclub.co.uk/bsaoc_forum/index.php?topic=4269.0 . not mentioning DEVIMEAD or anything .



ARRGHH . https://sites.google.com/site/bsadaytonaa5019661968/survivors

Toitie too , oi seys .


Far Out - https://sites.google.com/site/bsadaytonaa5019661968/1966


\ if youre running at Daytona , you might go for the bigger ports , and bigger carbs .

Be intresting to see a head of this / these . Wot .

And finalally , the OW 72 yamaha is a BSA rip off . https://www.xs650.com/threads/ow72-yamaha-factory-flat-track-racer-truth-rumour-and-innuendo.45687/

Theres period stuff / published on it . Have a ' CYCLE ' mag article on the development , as its the same sizes , the same sizes might be about right .

A earlyish ( 1980's ) Classic Bike . Had a few pages on his engines , pictures'n all . Prattling on about porting & suchlike . If you can find it .
some people say ' latest thinking is . . . ' but a A 65 is NOT ' latest Thinking ' understanding its persona could well be more productive .



Not the latest issue , but still available . 1

The ports on my head measure up at 30mm at the carb flange tapering down to +/-28mm just before the bowls. Ed V noted that the post 66 heads have a lot more material added to the bowl area, and that the earlier heads are better flowing in this regard. Just looking to move some torque down in the power band, hence my question about sleeving. Consensus is that the at .4 lift the 40mm valves can't flow much more than a 28/29mm port delivers, so I guess what I'm after is velocity rather than volume.

Id think its ideal as is , or 32 thru down to 30 , if your looking to tear balls off , with mega carbs .

Id use 1 5/32 Monoblocks .

Thought a defunct head might be the go to slice thru the port vertically , to see where the meat is .
the BOWL & flare to seat is the crucial area . The Yam. drivel would be worth deciphering -
as it is near identical - note he says 36 / 38 carbs - to beat a Triumph . but the Yam broke doing it ,
Wonder on a T 120 crank in a BSA , for a A 70ish , long rods for high rpm's if POWER is the game .
good for 8.000 at least .

Better as youve said , if its for the street - with straight thru glass pack . ' mufflers ' .