Author Topic: A10 alloy head and valves  (Read 900 times)

Offline Plammimam

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A10 alloy head and valves
« on: 14.08. 2018 16:33 »
I am rebuilding an A10 engine. When removing the alloy head I found all the valves to be 1.38 diameter. I can’t find any information on this configuration of valves. All I find is 1.38 for exhaust and then a variety of sizes for inlet valves. Can anyone advise what head this may be. Unfortunately the casting number has been erased but the combustion chamber is 70mm. Head has single carb with cast in inlet duct.
Appreciate any ideas

Offline duTch

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Re: A10 alloy head and valves
« Reply #1 on: 14.08. 2018 21:38 »
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 Plammimam

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Re: A10 alloy head and valves
« Reply #2 on: 14.08. 2018 22:41 »
Yes been there but nothing covers 4 valves all 1.38 diameter. I can get exhaust valves this size but not intake valves

Online chaterlea25

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Re: A10 alloy head and valves
« Reply #3 on: 15.08. 2018 13:21 »
Hi,
Thats a strange one???
Can you see if there were replacement valve seats put in ?
Some photo's would be good
The inlet seats could be cut out to suit "normal" size inlet valves
Or
Exhaust valves will be fine for inlet fitment ,
(but you usually cannot fit inlets in the exhaust position)

John
1961 Super Rocket
1963 RGS (ongoing)

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Re: A10 alloy head and valves
« Reply #4 on: 15.08. 2018 14:41 »
An A7 shooting Star head perhaps?
2 twins, 2 singles, lots of sheep

Offline Plammimam

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Re: A10 alloy head and valves
« Reply #5 on: 15.08. 2018 16:13 »
Here are some photos of the head. I am thinking this is an A7 head as I believe I can just make out a 22 in the casting number which might make this one a 67-1122. If it is then it has been modified by opening up the valves to 1.38 for all of them and machining out the combustion chamber to 70mm. If it is, it’s a good job. Suppose I could go the next step and open the inlet up to a larger size to match one of the A10 engines. As it happens my serial number is a Spitfire engine but that’s where it stops!

Online chaterlea25

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Re: A10 alloy head and valves
« Reply #6 on: 15.08. 2018 21:37 »
Hi Plammimam,
That looks as though the numbers were intentionally removed?
What size is the inlet port? does it look to have been opened up?

John
1961 Super Rocket
1963 RGS (ongoing)

Offline Plammimam

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Re: A10 alloy head and valves
« Reply #7 on: 16.08. 2018 08:55 »
OK think I figured it out, this has to be an A7 head modified. Looking at my pictures and comparing to the first reply with the link to Atlanticgreen pictures you can see my head does not have the step down from the gasket face to the chamber. More than likely from blending the head out from 66mm to 70mm. Some of the A7 head valves were all the same size at 1.3, therefore have to assume all valves were oversized to 1.38 (or I can’t measure right) now I know why I always call these bikes Bitsa’s. Time to consider what action next

Offline muskrat

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Re: A10 alloy head and valves
« Reply #8 on: 16.08. 2018 12:56 »
G'day Plam.
That's what I luv about these bikes.
When I converted my A7SS (early bolt on manifold "twin carb") to an A10 I chamfered the head to match the bore. Then with a bit of work fitted Super Rocket valves. My plunger has a "57 SS head with 1.41 inlet and 1.38 exhaust valves.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7

Offline Plammimam

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Re: A10 alloy head and valves
« Reply #9 on: 16.08. 2018 18:40 »
So suggestions on what A10 engine to make based on what I have
Modified A7 head with 4off 1.38 valves
67-334 cam
Flat top 7.25-1 pistons
Large journal crank
389/15 AMAL Carburetter (Velocette Venom)
A10 Spitfire serial number CA10 SR 55*
What would you make?

Online chaterlea25

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Re: A10 alloy head and valves
« Reply #10 on: 16.08. 2018 18:57 »
Hi,
I would find a 356 cam, and I think you have too much carb for the small valve head
(I wonder if the previous owner was building an engine for trials/ trail use?)

I built a bike with with flat top pistons, 650 ally head, 1 1/8in carb and a 356 cam  it ran really sweet
It is sooo different to my SR that has high comp, 357, fancy valves and 30mm Mikuni and siamise pipe with
goldie silencer,


John
1961 Super Rocket
1963 RGS (ongoing)

Offline Plammimam

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Re: A10 alloy head and valves
« Reply #11 on: 16.08. 2018 19:48 »
May be he was, here is a picture before I stripped

Offline muskrat

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Re: A10 alloy head and valves
« Reply #12 on: 16.08. 2018 20:47 »
G'day Plam.
I'd look at 8 to 8.5 pistons, 356 cam and 30mm monobloc or concentric carb. Would be easy enough to slot in a 1.41" inlet valve. Keep it looking pretty much as is.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7

Offline Plammimam

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Re: A10 alloy head and valves
« Reply #13 on: 16.08. 2018 21:08 »
Thanks

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Re: A10 alloy head and valves
« Reply #14 on: 16.08. 2018 21:37 »
Keep the flat top 7.5:1 pistons. Just right for modern (and future) petrol and keeps the bike sweet.
2 twins, 2 singles, lots of sheep