AMAL 289 questions

[Amal289]

Hello - I'm new on here, searching for knowledge.

I have an application for AMAL289 carbs mounted horizontally, eight of them.
OK it's on a car - please don't throw me off just yet.

The questions are:
a) what is the purpose of the tiny hole in the casting just above the mixing chamber union?
b) when mounted horizontally, how far below the main jet centre line should the fuel level be?

I'm a bit old for bikes now, but went through a 1956 Sun 125, 1953 BSA B31, 1935 Norton Inter, 1938  Vinnie Black Knight (never had it out of third in anger).

Hope you can guide me on the paths of righteousness.
Neil.
www.battenspecial.com

[john.k]

Funny you should ask,Ive been trying to figure this out for some years ,off and on.....Incidentally ,I think the hole you refer to is the air bleed for the idle system...as you should know ,idle adjustments do not adjust fuel ,but bleed air ,fuel is metered by the internal passages in the jetblock............Working out the fuel level is easy enough ,and I did that quite easily by comparison with a bike with a horizontal carb,of which there were quite a few in the 30s ....Triumph ,New Imperial ,Excelsior.etc...........I also found out virtually no one living today can amswer these questions..........Those that have these bikes ,generally bought them restored ,and so are clueless,as are the majority of prewar bike owners now .......cheque book restorations.

[chaterlea25]

Hi
These drawings might help,?
I would think that the bleed hole needs to be upwards if the carb is mounted horizontally ?

Plan to carry a decent fire extinguisher 

John

[R]

You do know that getting eight (!!) Amals synchronized is going to be half a nightmare !

Wasn't it said that the Guzzi V8 never ran on more than 7 cylinders at a time.
They were of course Dell'Ortos, but the same principles apply.

[33d6]

Eight horizontal mountings. Eight times more chance of a slide jam. We all know why the horizontal fitting craze came and went quite quickly.
I deeply respect a man who is willing to try for eight Amal carbs in harmony and horizontally mounted. Obviously someone with titanic patience or titanic determination.
I have to ask, what beast has such a set up? It would have to be some hill climb/sprint special of the 40’s or early 50’s.
Do tell.

[john.k]

I believe the late Freddie Dixon ,of Douglas fame had a Bugatti with eight Amal RN dirt track carbies mounted on it ........but not on their sides,I suspect.......Ive never been able to figure out how the idle circuit would work for starting with the carb horizontal,without spilling fuel all over the magneto mounted underneath.....but Triumph were an adherent of the sideways Amal all through the 30s.....so it must have worked .......Ive never found anyone who could say if the horizontal was different internally ,and how they were different.......Unfortunately ,most millenials who own 1930s Triumph singles paid a large sum for them ,and consequently dont ride them ......fearing sudden devaluation of the investment on contact with an immovable object........or meeting another millenial playing with a device while driving......They will tell you how cool they think their cycle is,and thats about it.

[mini-me]

You would be far better off talking to Burlen who make the carbs.

[Rex]

Be better off fitting more suitable carbs. Those horizontal jobbies, apart from being both very old and rare, would take up a lot of real estate when mounted in a bank. Wouldn't a set of new vertical 289s with one larger remote float chamber per bank be better?

[john.k]

Shoulda looked a bit closer ......not horizontal as in Triumph ,but downdraft with a horizontal slide ........Oddly enough ,in an old car book somewhere I have details of an Amal slide carb mounted downdraft,I know Douglas used one mounted updraft inside an airbox.........Instead of a Bugatti straight 8 ,he s got an old Ford flattie boat anchor...........Id certainly suggest 8 Strombergs ,just the same as my beach buggy of the 70s ,a Ford 292 Customline engine with 8 Strommies from sideplate Holdens.........and a small Blitz diff with aeroplane tyres.

[Amal289]

Thank you all for your interest and suggestions.
I'm stuck with AMALs because that's what the car had pre-war when racing at Brooklands. It's the Batten Special with a side-valve Ford V8 engine from 1933-ish. The special cylinder heads and carbs got lost in the 1950s. I've had the beast almost fifty years and want to re-create the pre-war configuration so downdraught AMALs it has to be!

I don't understand the purpose of what is variously labelled pin-hole or air bleed. If it's important, and I assume it is or it wouldn't be there, it could be moved to another position by careful drilling of the jet block and main casting.

Thanks to John Chaterlea for the drawings - would it be possible to have a copy of the jet block drawing without the watermark? By email, maybe?

The intention is to have one "float" chamber between the two banks of carbs, but without a float - instead the level will be maintained by constant flow of fuel into and out of (back to the tank) a sealed box, always at atmospheric pressure.

Here's the car in action: www.battenspecial.com

[chaterlea25]

Hi
Sorry that is the only image I have, (pilfered from some other website )
Fantastic project  though 

John

[JFerg]

Back at the original question;

1.

[JFerg]

Don't know what happened there....

1.  Holes are for the intake of air at idle, but that's not going to be an issue in this case.
2.  Fuel level in a vertically mounted carb is, in the perfect world, just below the jet in the choke such that when the throttle is opened, fuel will seep into the choke by surface tension.  When the engine is not running, of course.  In practice, a smidge below this is perfect and does not dribble.  With the chokes and jets horizontal, the same principle will apply.  The highest level where it won't dribble out unassisted.  Note that this is the fuel level, not the float level, which is a very different thing.
With the standard type 29/289, there's a drilling through the arm of the float bowl.  This is blanked with a little screw opposite the drilling on the mounting flange of the float bowl.  Replace that with a little adapter screw and a pit of clear plastic tubing tied to the side of the carb and you can see the fuel level precisely.

[Amal289]

1.  Holes are for the intake of air at idle, but that's not going to be an issue in this case.

Thanks for that JFerg, but, forgive me if I'm being thick, there is only one hole under consideration - in the side of the mixing chamber casting just above the thread for the bottom union to screw on. It's a pin hole and appears to feed through the jet block into the cavity around the needle jet. What's it for?

As described above, there will be no float bowl attached to the carbs which will be fed from a common fuel reservoir, but I take the point about a transparent tube level indicator. In the horizontal, downdraught configuration where should that level be in relation to the main jet centre line?

By the way, in consideration of the difficulty in synchronising eight of these wee monsters I have been reminded that in 1938 the approved method was to remove the exhaust manifolds and, in a darkened workshop, tune to the colour of the flame exiting the exhaust ports. Nice bright blue is good. Some Aston Martins had small plugs screwed into the top of each exhaust pipe, close to the cylinder head, which would be removed to allow viewing of the flame shooting past. These days we have Gunson Colortune plugs. Since I already have a kit I asked Gunson to supply just seven plugs to save me having to buy complete kits. They declined, so I made my own 18 mm. see-through plugs to assist the tuning.

[R]

This certainly is an interesting question.
I think you should refer to these carbs as being mounted 'vertically' or 'downdraft'.

I've got a prewar carb thats mounted on its side, and you can see the fuel level marked with the marker pen black line.
I know this is not very scientific, or measurable ...
But it gives an indication the fuel level is just below the horizontal of the jet level.
I wonder if you need to make your fuel arrangement with a bit of adjustment up/down incorporated.
as you may need to experiment a bit with fuel height ?


I can't help wondering though that g-forces are going to interfere a bit with the fuel level,
since cars don't corner like motorcycles.

Also, Amal TT type carbs would probably add a trace more performance (no needle to interrupt the airflow)
and would have been available prewar.  In brass, and uber expensive for a set of 8  !!?  And heavy ...

That hole is covered up when the jet block nut is done up ?

Have fun !!, keep us posted.