|The MGA With An Attitude
Driving With Only ONE CARBURETOR - CB-113
On 09 October 2008, Mike Ellsmore in Victoria, Australia, wrote:
>A club member's car was noticed to be leaking fuel profusely at a recent clubhouse night meeting. Closer inspection revealed the grommets on the front carby holding the float chamber to the body had failed. No one had a spare so a tray truck was called to cart the wounded car home rather than risk a fire.
>This incident got me thinking (dangerous!). Could the tow truck have been avoided by making it a one carby set up. Remove both banjo bolts that connect the fuel hoses to the carbys and swap over the banjo unions so the single entry is on the back carby - connect up the fuel line to the rear carby only. Release the coupler on the front carby throttle shaft and away you go on one carby! They run okay on one carby when tuning - would this set up work in an emergency to get you home? Has anyone done this?"
The anwers and yes, and yes. Next time if you think quicker you can save the towing bill. The original fuel hose running from rear carb to front carb can indeed be installed between the metal fuel pipe and the rear carb, plenty long and all the same threaded fittings.
The engine will run fairly well on only the rear carburetor if you disconnect a clamp on the throttle shaft to leave the front carb closed. I did this once many years ago when I inadvertently left the shaft clamp loose after a tune up. Behavior of the car was almost normal with engine speed under 2500 rpm, just requiring a bit more pedal to make it go. It would still cruise about 60 mph on a level road, given enough time to get up to speed. Unfortunately I was autocrossing that day and didn't have time to figure out what was wrong with it until I was back home at day's end.
At higher engine speed the torque will suffer dramatically. It can be tough to get it much over 4000 rpm in 2nd gear with full throttle. At that speed it will seem to be running on two cylinders due to air flow restriction in the cross over tube of the intake manifold, and of course only one carburetor passing air. But it is certainly good enough to get you home without a tow. This doesn't work as well with the other carburetor, as the throttle cable and arm are connected to the rear carb, not to the the intermediate shaft.