Author Topic: Valve sizes for Alloy heads  (Read 495 times)

Online orabanda

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Valve sizes for Alloy heads
« on: 30.05. 2017 13:58 »
        Hi all,
        What is the diameter of the inlet and exhaust valves for:

        • 1954 A7SS alloy head (separate inlet manifold)

        • 1956 onwards A7SS alloy head.

        • Road Rocket head.

        Thanks,

        Richard

Online beezermacc

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Re: Valve sizes for Alloy heads
« Reply #1 on: 30.05. 2017 19:46 »
A7SS  1954/5/6/7 inlet 1.315"  Ex 1.285"
RR with head 67-1126, inlet 1.415"  ex 1.38"
Priory Magnetos Ltd - A10 spares, magneto and dynamo refurbs. www.priorymagnetos.co.uk

Offline muskrat

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Re: Valve sizes for Alloy heads
« Reply #2 on: 30.05. 2017 21:06 »
G'day Richard.
A bit of info here http://atlanticgreen.com/a10dph.htm
I have a 54 A7SS (1102) head fitted with the A10RR (1102/6) valves on the 57RR+ Cafe (1.41 & 1.38). My original 57 A7SS head (1122) is fitted with the same on the 51 plunger. The seats are big enough to take a little porting to accommodate the larger valves. I recently (after the big bang) fitted the early SR valves to the 1102 for reasons of better cotter retention. I had to use the A7SS springs and hardware but modify the top collar to take the SR cotters.
 *work*
Cheers
'51 A7 plunger, '57 A7SS now A10CR, '76 XT500, '77 AG175 '83 CB1100F, '81 CB900F project.
Australia
Muskys Plunger A7

Online orabanda

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Re: Valve sizes for Alloy heads
« Reply #3 on: 31.05. 2017 00:05 »
Gentlemen; thanks!
Was it a worthwhile performance improvement to fit the A10 valves to the A7SS head?

Offline muskrat

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Re: Valve sizes for Alloy heads
« Reply #4 on: 31.05. 2017 13:46 »
G'day Richard.
I'd have to say yes on the A7SS racer. I never did a dyno but she got closer to the pointy end, a lot more 650's & 750's behind than in front. She was 2 mile per gallon thirstyer, I got better mileage out of my 4.2Lt Landcruiser.
I'd also say yes on the A7 plunger. The look I get from modern pilots when I'm only 50 meters behind at the top of Barrengarry Mountain. *grins*
Cheers
'51 A7 plunger, '57 A7SS now A10CR, '76 XT500, '77 AG175 '83 CB1100F, '81 CB900F project.
Australia
Muskys Plunger A7

Online orabanda

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Re: Valve sizes for Alloy heads
« Reply #5 on: 31.05. 2017 16:15 »
Hmmmmmm..... suspect being in front has more to do with the rider, than the bike!

Offline muskrat

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Re: Valve sizes for Alloy heads
« Reply #6 on: 31.05. 2017 20:47 »
G'day Richard.
Bigger valves (ported to suit) means more in, bigger bang and faster out = faster.
I ride any bike like I stole it but I'd guess Casey Stoner riding a postie bike would flog me. *lol*
Cheers
'51 A7 plunger, '57 A7SS now A10CR, '76 XT500, '77 AG175 '83 CB1100F, '81 CB900F project.
Australia
Muskys Plunger A7