VHA 1952

[david.anderson]

The quoted figure in the 1950 handbook for a VH is 24.6bhp
The quoted figure in the 1952 handbook for a VH and VHA is 24.6bhp
The quoted figure in the 1953 handbook/supplement for a VH and VHA is 24.6bhp
The quoted figure in the 1957 handbook for a VH is 26bhp
Somewhere, although I cannot find it, the figure for a 1950 VH with 7.5 piston is 27bhp
On the flow bench the iron VH head slightly out flows the others and as such will perform better.
While I did not put my VHA head on the flow bench I can say that the port floor is too low for both inlet and exhaust ports. (While my head may have been ported and not be original, I believe it is original as it is the same as another VHA head that I looked at). There is no way that the flow would turn the corner at the port floor, rather the flow would separate and the result would be a lower overall flow figure. There is inadequate support for the valve seats and I would not be surprised if they were to move. The spark plug location on the VHA head is further from the centre of the combustion chamber than with any of the other heads.
The 54 alloy head has a turbulent flow and with minimal work to reduce the turbulence, will match the iron head.
The 56 alloy head as supplied by Budgen has a very turbulent flow and as a result the overall flow figure is less than it should be. The iron head both flows better and is less turbulent and as such should perform better. The iron head can also be ported (have material removed from the roof turning into the bowl) a little to improve flow but in the same area the Budgen head must be filled in with weld to improve the flow.
The inlet port in the original 56VH alloy head is better shaped than in the Budgen replacement and flows a little better.
While these heads were advanced for their period, they can be greatly improved with modern technology.
It was actually common at one time to fit iron VH heads to a Harley for a considerable performance increase.
David

[Leejm]

In the ariel story book it does say the VHA gave over one more horsepower for the same piston as it's iron counterpart. I have also read it in another place which I can't remember right now, but in the sales brochure the VHA is just put with the Vh for the same figure of 24.6.
There is no doubt the ports are different to the iron motor what difference if any it makes. And the spark plug location is also different to any other single built. There must be a reason they did this. Lee

[ben.mitchell]

This is indeed Lynne's VHA and Neville maybe could have recognised it from the Australian Ariel rally in Tamworth NSW in 2015. From the other posts, you guys appear to know more about the VHA then me (or Lynne for that matter!). She only used the VHA for the 'round the world via the colonies' trip as we wanted parts compatibility so we were both on all alloy 500 singles, but Lynne's reduced stature makes an s/arm frame a bit tall so it had to be a VHA for her...in an Anstey Link frame to give some riding comfort. As far as I can remember the tank was the original one but I could be wrong...Adrie, may I ask why you think it is an Indian one? I can only tell the difference when I try to fit the tank badges..as the hole spacing is sometimes incorrect on the pattern Indian tanks.
In respect of colour, I understand that Ariel had a standard colour for each model in each year but you could otherwise have whatever colour you liked. Her Majesty was crowned in 1953 and her favourite colour was (and still is as far as I know) Wedgewood blue, hence the more desirable Ariels in 1953 (VHA, KHA and 4G) had this as the standard colour. Lynne's VHA is actually from 1952 in any case! Funnily enough, the Archbishop of Canterbury who popped the crown on Liz's head in 1953 had previously been the headmaster at Repton School while Roald Dahl was boarding there and Roald secretly kept a Red Hunter in a lock-up garage in the neighbouring village of Willington...every day you learn something new!
While Lynne is now enjoying a more modern 650cc single (with electric start etc.) she wants to keep her '49 rigid MKI square four but her '52 KH, '50 VCH (magnesium c/cases but Anstey link frame) and her '36 cammy will all be sold to make way for a planned house move as I do not want to have to move all the bikes.

[adrie.degraaff]

Adrie, may I ask why you think it is an Indian one?

"It could be an Indian one or the bottem taken out for repairs" becouse the bottem ridge welding is uneven like a treesaw.

But if the the tank has left the factory this way than i am so ashamed .

[nevhunter]

The Iron Sportster heads have very large ports which don't help till the engine is increased in capacity. the velocity is too slow for maximum performance. Bigger is not always better with ports. . A set of tracker based heads with the valve angles reduced and smaller posts, flowed and swirl ground valves gives more torque over the whole range with a 43% increase at one point without any cams being changed. The alloy material allows a much higher compression ratio without detonation. That's the main advantage of the alloy material. On the downside, you will have much more trouble with seats moving guides moving and the holes in the head close around the "Bolts" when the metal softens IF the material isn't right up to scratch. Many considered the ALLOYs of the period were a problem with some bikes. The iron head is relatively trouble free and does port well. All those hemispherical heads are not the best for High compression as they are too deep and a HC piston has to have a high crown and exaggerated valve relief cutouts resulting in a bad combustion chamber shape and a large area exposed to the hot gases, requiring extra piston clearances. Nev

[paul.jameson]

David,

You say that the iron VH head performs best on the flow bench but can you clarify which head this is please? Is it the early head without the head gasket or the later one which used a head gasket? The late Bob Brassington used to swear blind that the later (iron) head had been detuned by BSA to prevent Ariels from out-performing the parent company's bikes.

Ben,

If you need help in moving out Lynn's bikes or any spares, etc. let me know and I will come along with a very large van to do all I can in clearing your old premises!

[david.anderson]

Paul
I am referring to the early VH head, no head gasket and factory ported. I have never had a big fin iron head in my hands let alone on a flow bench.
I just opened the carb on my VHA and had a look down the inlet port as well as a caliper. It is certainly bigger than the iron VH port but I can also see the edge of the valve on the seat. In this regard it is similar to the iron NH inlet port. I could not get the iron NH inlet port to flow as well as the alloy NH port.
David

[ben.mitchell]

Paul
Thanks for the kind offer..do you need any iron KH or MkI square four engines..? Have you finished your s/arm four yet?

Adrie
Thanks for the tip, next time that I go to the shop that is selling the VHA for Lynne then I will have a look at it again.

[Simon.Gardiner]

David,
The late Bob Brassington used to swear blind that the later (iron) head had been detuned by BSA to prevent Ariels from out-performing the parent company's bikes.

I've got a '51 'small fin' iron VH head and the '53 'big fin' equivalent and if there are any differences in the porting it's very difficult to see!

SG

[paul.jameson]

According to Bob, the valve guide gets in the way of the flow far more on the later iron VH head than it does on the early one. Quite what he meant by that I don't know, never having had a late iron VH head either, and it is fast coming up to 10 years since the last opportunity to ask him.

Ben,
I have no need of iron KH or Mk I Square engines at present, but many thanks for the offer. The swinging arm Square has been somewhat overtaken by my Healey project but I get more and more tempted every week to get seriously started on it. As ever, cash flow is the main issue and cash is flowing into the Healey project in rather greater quantity than I had hoped!