Carb question...Dave?

[scumdog]

Tinkered with the carb (4100) on my '66 as the idle was too high and a mate who had been driving behind me reckoned it was running a bit rich.

So I took the top off it to check all was well there - and found out 'somebody' had put the top gasket in back-to-front and it was'nt sealing the small 'tube' between top and bottom half at the rear end.

So can anybody enlighten me as to the effect of the gasket being the wrong way around?

It's in correctly now, I haven't noticed any difference but I've only driven a couple of miles since then.

[scumdog]

Anybody gave any idea re the gasket thing?

[Yadkin]

Not sure what the "tube" at the "rear end" is.

To see if you are running rich, look at the color of your spark plugs. You can always go down one jet size and then re-diagnose.

[scumdog]

Not sure what the "tube" at the "rear end" is.

To see if you are running rich, look at the color of your spark plugs. You can always go down one jet size and then re-diagnose.

I will look into that aspect.

But if you look at the main gasket on a 4100 you will see what I mean - or conversely, if you look at a 4100 with the top off you will see the 'tube' built into the casting in the centre-rear of the carb, it runs vertically.

Fitted the correct way around the gasket seals that 'tube' that runs between the body and the top of the carb

[jopizz]

I doubt having the gasket backwards would cause your car to run rich. The idle mixture screws out of adjustment is the most likely cause of that. You might only notice it at high speed if the path between the primary and secondary bowls wasn't sealed correctly.

John

[Yadkin]

I will look into that aspect.

But if you look at the main gasket on a 4100 you will see what I mean - or conversely, if you look at a 4100 with the top off you will see the 'tube' built into the casting in the centre-rear of the carb, it runs vertically.

Fitted the correct way around the gasket seals that 'tube' that runs between the body and the top of the carb

See the picture from my spare parts collection. The body is on the bottom and the cover is flipped up. The "tube" next to the center threaded hole (for the stud that holds the air cleaner in place) is a vacuum port. That port is vented on the cover by a thermostat.

I'm guessing, but the thermostat probably opens when hot, and could possibly be part of a circuit that changes the fuel mixture.