Author Topic: A10 alloy head and valves  (Read 905 times)

Online chaterlea25

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Re: A10 alloy head and valves
« Reply #15 on: 16.08. 2018 22:43 »
Hi All,
Quote
May be he was, here is a picture before I stripped

 It always helps to see an "overall picture"  ;)

John
1961 Super Rocket
1963 RGS (ongoing)

Offline coater87

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Re: A10 alloy head and valves
« Reply #16 on: 17.08. 2018 08:08 »
 Holy cow,

 My eye sight is not what it used to be.

 I wondered what the metal loop was coming out of the handlebars for about a minute before I realized it's the mower handle.... *eek*

 Lee
Central Wisconsin in the U.S.

Online morris

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Re: A10 alloy head and valves
« Reply #17 on: 17.08. 2018 08:41 »
Holy cow,

 My eye sight is not what it used to be.

 I wondered what the metal loop was coming out of the handlebars for about a minute before I realized it's the mower handle.... *eek*

 Lee
*lol* *lol* *lol*
Don't push it to far Lee. You guys already invented the apehanger. That'll do...  *smile*
'58 BSA A 10 SA
'52 BSA A 10 Plunger
'55 MORRIS ISIS
The world looks better from a motorbike
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Offline duTch

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Re: A10 alloy head and valves
« Reply #18 on: 17.08. 2018 09:10 »

 Yep- I'll second flat-tops, I have them on mine, but with a 357 cam and bigger valves (can never remember the size, but both much the same I think ?/??), goes fine....My El Plungioe is also the Scrambler style which I like, and sooo fun to ride
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
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Online muskrat

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Re: A10 alloy head and valves
« Reply #19 on: 17.08. 2018 14:02 »
I just thought if Attol wanted it to go as good as it looks higher comp pistons would give it a bit more punch. 8:1 wouldn't stress anything and still easy enough to kick start. (says the man with 10.5:1's) *shh*
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
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Muskys Plunger A7

Offline Plammimam

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Re: A10 alloy head and valves
« Reply #20 on: 17.08. 2018 14:54 »
Hmm, when you have size 7 feet and weigh 145 pounds another .75 of compression ratio can be difference between starting the bike or laying in the hedge. Or I could wear divers boots🤣
When I was 16 a pal of mine had a 1959 500 Goldstar. We would have competitions with all the lads to see who could start it. Even with valve lifter and decompressor I never got any noise!

Offline duTch

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Re: A10 alloy head and valves
« Reply #21 on: 17.08. 2018 19:22 »

 Those fork-shrouds almost give it the look of modern 'upside-down' forks  *wink2*
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
Australia

Offline Peter Gee

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Re: A10 alloy head and valves
« Reply #22 on: 21.08. 2018 17:56 »
My A7SS head has almost identical valve sizes, the difference between exhaust and inlet needs a caliper to tell. The head is standard.

Obviously an A7 head can take a lot bigger valve , though you would have to have someone knowledgeable and with  a Sardi type machine to do the job proper. Then you would need port work and to step up the carb to maybe a 389.

I always wondered why BSA did not put more punch into the A7SS by opening out the inlets and etc. Maybe they just wanted to keep it as the very sweet engine it is.

Offline Sluggo

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Re: A10 alloy head and valves
« Reply #23 on: 21.08. 2018 20:36 »
Valve size alone does not determine performance, and neither does compression.  Its all about the total package.  Personally I feel 7:1 seems rather anemic, but what do I know? 

I know a guy up in BC Canada who helped get TRIBSAs legal and into a popular race class in AHRMA MX racing here in the US.  (He is from UK Originally and has a lot of race history including ISDT).
So Ken, and a few others finally got the race organization to allow the TRIBSAs and he and others went to work feverishly building what they thought would be the ultimate race bikes.
A10 SA frames, Preunit Triumph motors and most wanted the 500cc twins, although some went big into 750 big bores (Different classes).  In Kens case got the alloy close pitch fin cyls and heads and then had head work done, and HIGH Compression pistons and big lumpy cams.

It was a beast, snarled and bucked, fearsome.

However he had a lot of trouble with it, It pulled out cyl base studs and other hardware issues, and basically every race outing was a DNF or serious other mechanical problems.  From a variety of inputs he finally concluded to redo it and De-Tuned the motor, Lowered the compression, different cams and it turned out in the lower state of tune it had more than enough  power but importantly was instead of raw power he finally dialed it into low end grunt and mid range that was more useful, especially on West coast tracks where high speed was not a factor.  Most importantly the bike didnt try to kill itself and he started winning races.

When I was in my 20s I owned 2 Chevy Hot rods, Both Novas, a 1972 Rally Nova and a 1964 SS.  I was convinced after years of research and all the popular magazines that bigger was better and built a variety of Small blocks trying to push the envelope, Big cams, big valves and heads and all the Go-fast parts my meager budget would allow.  I finally got the opportunity to get a Big Block motor and it was a 454 and rectangle port heads and a variety of performance parts on it.   It WAS fun! And had more power than any person could use on the street.  But it was VERY expensive to build, and run, not to mention it had poor manners in driving.  I actually took a young lady out in a date in it and she concluded I was an idiot, why would you want to own a car like that?  (Lets just say City driving was a challenge).  (There is a substantial weight gain with a BB over a SB as well)

In my daily driver hotrod, the 63 SS I had a 283 SBC and I learned to love that motor.  For a small car it had a ton of power, I could beat many other cars on the road, but behaved nicely in any traffic or conditions.  It had stock compression, very small valves and the intake ports in the heads and manifold were small as well.

What I learned was for low end USEFUL power, it was about velocity, not mass, Small was better. Chevrolet knew this as well and this was called the "Power Pak" option.  While I still love building big motors, The little 283 in a light weight car is one of the best versions out there.  Some racers knew this as well and slightly tweaked them into 302 and 305 configurations and they dominated SCCA Trans AM sports car racing in the 1960s and early 70s.

I would surmise that this head with the small valves would be interesting to do some testing with, as well as try with a variety of cams and I bet in the right configuration of cams, compression and carb (Assuming timing and spark quality are optimized) that this could be a very powerful engine for certain applications.   I doubt anyone will do Trials bike riding with a PU BSA Twin, But dialed in right it could be a potent street or Dirt racer.  Dont overlook the exhaust pipes, They need to be optimized for this configuration as well.

Much like the 283 Power pak vs a 454 BB, I would look into it before hogging out the head and changing parts.  Many of the best and brightest who used to build performance versions of these motors are either deceased or one foot in the grave, So not a lot of resources to ask anymore, but perhaps some documentation exists on alternatives to monster motors.
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Offline Plammimam

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Re: A10 alloy head and valves
« Reply #24 on: 21.08. 2018 21:02 »
Thanks, that’s a really useful read. My plan is to leave the head, valves and pistons as they are and add the 356 cam which seems to gel with most thoughts on the forum and off
Thanks all

Offline Sluggo

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Re: A10 alloy head and valves
« Reply #25 on: 21.08. 2018 21:41 »
I looked at my favorite supplier for valve train parts, Kibblewhite Precision Machine and I prefer their products over anyone else's.   However they dont stock valves in your sizes.   Their quality however is excellent and I have been using their products for nearly 3 decades.  (Guides, springs and valves).
Nortons especially have a lot of suspect products in the supply chain both OEM and aftermarket and stock valves have a habit of dropping pieces into the rotating assy. (There was bad batches and no way to tell, simpler to replace with a known entity) Being that the KPMI  are Stainless valves, Problem solved.

But I have not researched much on BSA valves availability, but I have a friend who runs a shop that does machine work and specialized engine building and he often has to build using non stock parts reconfigured  for obsolete applications.   Perhaps there are other applications that use the valves you need for a rebuild?
I looked at just valve sizes alone, and it appears some of the Unit singles for BSA might be close?  I am sure someone has figured this out.   I have a lot of misc British Bike parts and if you post the dimensions I can compare to some of mine.   See the KPMI catalog for a print diagram of critical dimensions. 

I used to be a dealer for them, But dropped my dealer status when some bright bulb decided to retain my status that I & others had to order the entire product line, not just the narrow applications I used.  I was not prepared to stock parts I would never use.  (This is not a uncommon problem)  However I still love their products and assume that idiot moved onto a new company.

See: https://www.kpmi.us/catalog.html

They DO carry a wide variety of BSA valve train products and you will find the BSA range on pages 11-17

(I currently have some of their stainless valves for Triumph, Norton and A65 BSA on the shelf, if you want pictures I can post them, I have always been 100% happy with their products, and built many motors using them, have had 0 problems or failures)
Remember that any advice received on a free internet forum is generally worth about 1/2 of what you paid for it.
We overcharge every 3rd customer to pass the savings onto you.
You can have High Quality, Low price, and fast turnaround. Pick any 2, Never all 3 at the same time.