Alternative to auto choke?

[cswagon]

I've have just fitted a pair of N.O.S. Stromberg 175CD carbs (4027L/R) to my Rover 3.5 which is in a Landrover Series 1.
These carbs are normally fitted with the F.A.S.D. auto choke system but didn't come with this unit when I bought them.
After talking to various people I'm more than a bit reluctant to use it anyway due to it's supposed poor reliability, so I'm looking for an alternative.
Apparently, you can't fit a normal manual choke to these carbs because, although the body looks the same,they don't have the necessary internal drillings to suit.
Does anybody therefore have any suggestions or experience of fitting a different method of choke?
Would fitting some sort of flap in the air cleaner intake port to restrict the air flow when cold act the same as a crude choke?
Any help or suggestions will be greatfully received thankyou.
Many thanks
Graham.

[Paul B]

I've have just fitted a pair of N.O.S. Stromberg 175CD carbs (4027L/R) to my Rover 3.5 which is in a Landrover Series 1.
These carbs are normally fitted with the F.A.S.D. auto choke system but didn't come with this unit when I bought them.
After talking to various people I'm more than a bit reluctant to use it anyway due to it's supposed poor reliability, so I'm looking for an alternative.
Apparently, you can't fit a normal manual choke to these carbs because, although the body looks the same,they don't have the necessary internal drillings to suit.
Does anybody therefore have any suggestions or experience of fitting a different method of choke?
Would fitting some sort of flap in the air cleaner intake port to restrict the air flow when cold act the same as a crude choke?
Any help or suggestions will be greatfully received thankyou.
Many thanks
Graham.

I've removed the choke mechanism entirely off my last two carbs, a Weber 500 and a Weber 38dgas. A couple of squirts on the throttle before starting the motor, then keep it running with your foot for a minute, and it is okay.

That might not be to everyone's taste, but I found trying to adjust the stock chokes so they worked, yet revved within neighbour-friendly noise thresholds, was a ball ache.

[cswagon]

Thanks for the reply Paul.
I'm not sure if you get any fuel when you hit the pedal on Strombergs without the engine running,do you?
What are your views on the "choke flap" method,do you think it might work?
I suppose the easiest way to check it would be to tape a piece of cardboard partially over the intake opening and see if that works.
Thanks again.
Graham.

[katanaman]

whatever you do you better make it strong as there will be a hell of a force on it, a cardboard flap is probably going to end up in your engine somewhere. Proper choke flaps are sprung so they can spin out the way when the engine is under load. Assuming you have an electric fuel pump you should get fuel on pressing the throttle, engine running or not. Have to admit I don't know the first thing about these carbs so if they don't have an accelerator pump then ignore me.

[ChrisJC]

Strombergs & SU's do not have an accellerator pump. They rely on the damped piston moving slowly up to provide enrichment. So pumping the throttle will do absolutely nothing!

The way the choke worked on the older SU's was to lower the jet, on later ones (HIF) it had an extra choke jet. Note sure about strombergs.

I found FASD perfectly reliable when I ran it for a year or so in my landie, but I ditched it when I went for SU's.

You could try bodging it with something stronger than cardboard!, but your best bet might be to fit a pair of manual choke carbs of some sort.

Chris.

[cswagon]

If I hadn't just laid out sixty of my hard earned on these n.o.s. Stroms then I probably would try some others ,or if I'd known when I bought them that they wouldn't run on a manual choke then I obviously wouldn't have bought them.But that's a lot of if's, and now I have them and they are on, and do actually run very well once you can start the engine from cold, then I will try all avenues to overcome the choke problem if at all possible.
I take on board what you say about cardboard and will probably try a jam jar lid or something just as solid to test the theory.It's purely just an experiment to test whether the vehicle will actually start just by restricting the intake of air and if it does then I can start on designing something a little more suitable that can obviously be controlled from the cab.

[Paul B]

Strombergs & SU's do not have an accellerator pump. They rely on the damped piston moving slowly up to provide enrichment. So pumping the throttle will do absolutely nothing!

What happens to enrich the motor when you stamp on the throttle big time at low rpm?

Something has to give a squirt of juice, else it'll run like a sack of spuds under hard acceleration.

I thought the piston moving up was to slowly open the throttle mixture as you accelerated, for economy?

Or is all this the very reason people don't use them on performance motors.

[ChrisJC]

When you stamp on the gas, the piston starts moving, but slowly. The increased airflow through the venturi causes extra petrol to be drawn in. As the piston rises, the airspeed drops (because the venturi gets bigger), and thus less extra fuel gets drawn in. Eventually the piston will reach an equilibrium position at which point the needle & jet are providing the designed mixture.
http://en.wikipedia.org/wiki/SU_carburettor

Chris.

[kiwicar]

with regard acceleration enrichment
with regard the choke it is done with an internal choke circute on the stromberg, it is why they are thought by many to be inferior to the SU as the drillings that are made for the choke always get bunged up with crud (oh and that they are die cast in cheepo zink/ally "white metal" rather than ally that is then machined).
Before you go modifying them I would consider putting them on Ebay and see if you can get your £60 back (or as much as you can) and either get the ones that will take a manual choke or invest in some SU's. If it were me I'd go for SU's if you can find some in good condition, but don't buy ones that are worn as they are just huge amounts of grief.
Sorry rambling again.
Mike

[cswagon]

Hello Mike
That's exactly what I've done.
Cheers Graham.