SpAriel MkII aka The Hermanator

[Vincent.vanGinneke]

Lunch almost ready !

And who recognises this oil line ? is it Ariel?
I want to cut out the twin banjo in the middle, but maybe it's a rare part.....

[Vincent.vanGinneke]

Bought this nice bit of casted alloy today at the Central Classics show in Houten, Holland.
Vendor told me he had bought it about 40 years ago, but never had a use for it, now I can have a go with it.
Plan to make a intake manifold that takes centre carb needle and centre valve stem 7 inch apart.
I dont remember where I got this info from but now I'd like to experiment a bit with the '40 RH engine.

15cm long so I can even screw up the first one!

and add some Roland Pike venturi sauce to it :

This was discussed a while ago on the forum, sorry no link
Plan is to have the Pike bit nearest to the head, rest of the inlet track ( 64mm minus 24.5mm = 39.5mm ) is straight

[john.whiting]

The oil line is the rear cylinder head oil drain from a preunit Triumph twin,maybe a Speedtwin

[Vincent.vanGinneke]

Thanks !

[david.anderson]

Vincent
The optimum tuned inlet length varies with the engine revs and the cam duration etc. When fitted with a HS cam a computer program gave me the following optimum lengths measured along the port centre-line from the valve seat to the carb inlet.
7000rpm - 8.38”
6000 rpm – 9.9”
5000rpm – 12.1”
4000rpm – 15.56”
So it is not a case of one size fits all. And there is of course the possibility of doubling a length to work on every second pulse.
I have made up a couple of extended manifolds. One uses a series of pieces and different length carburetor studs to suit. With the other one I curved the manifold down to stop the carb from getting too high.
On both I used the tapered venturi as recommended by Roland Pike and I reduced the manifold dia from 32mm down to 25mm at the venturi. As I considered flow may be detrimentally affected I tried the manifolds on a flow bench and found flow was unaffected by the venturi. As it is difficult to fit in a long manifold I also made a velocity stack for the carburetor to give an overall longer inlet length. The velocity stack as shown however did detrimentally affect the flow. The problem is the square end on the stack reduces flow. If I pack plasticine around the end of the stack and form a radius into the stack flow returns to normal. I will be turning a radius piece and will weld it to the stack. But as most of my bike work is on hold that will have to wait.
On the road the seat of my pants was unable to tell any difference in performance with the various length that I tried but a dyno may show a small improvement.
David

[Vincent.vanGinneke]

Thanks David, that gave some facts to think about.
If I get this correctly these lenghts are from the entrance of the carb inlet manifold up to the port centre-line.
What is the lenght of the manifold between the carb and the head in the first picture ?

[david.anderson]

Vincent
The manifold in the top photo is 52mm long. In the bottom photo each piece is 20mm there are 2 installed and one in my hand.
David

[paul.jameson]

My RH500 has a racing pedigree. Sadly, I don't have the original engine or many of the parts from it which were spread to the four winds when we were young kids and failed completely to recognise what we had in front of us.
But, I do recall that the inlet tract was extended by means of longer carb studs and a series of tufnol spacers between carb and head. What the total thickness of the spacers was I don't know and my guess after almost half a century would be unreliable, to say the least, but they were about 1/4" or possibly 5/16" thick. Variation of the number of spacers would give you some control of the variables described by David Anderson.
If anyone happens to own EGR 351 here in the UK, the long studs and spacers may still be fitted. But don't get too excited - they are (as far as I remember) the only bits from the racing engine on that bike.

[Vincent.vanGinneke]

Yep, the older I get the faster I was

[Vincent.vanGinneke]

found this bit of text on a metering rod inside the oil line on a KH.