Emissions different in each exhaust pipe

[344739lv]

My 1961 Mk 2 3.8 is fitted with 2"carbs, polished inlet and stainless steel manifold and exhaust.
I have been servicing the car but notice that my CO2 gas tester gives me different readings from each exhaust pipe. The carbs are in balance, and adjusting them seems to make a difference in 1 of the exhausts - the other stays fairly static.

The static exhaust is reading 1.7% the one that changes is set at 6.5% but can be influenced easily.

I am fairly confident there are no blockages so can't figure it out.

Is there a problem?

Tim

[piman]

Hello Tim,

are they HD or HS carburettors? If the former, then possibly there is a problem with the adjustment system, e.g. corroded spring in the base of the carburettor or some such fault. The easiest way to check is to remove the dashpot and piston assembly, adjust the mixture screw and observe the jet, you should see it move as you turn the screw? Another possible fault, although rare, is the needle loose in the piston?

Alec

[344739lv]

Alec,

The odd thing is that any adjustments on either carb will influence one exhaust emission but no matter him much adjustment on either the other exhaust reading remains static

Tim

[piman]

Hello Tim,

OK, that really is peculiar, my first reaction is a blocked exhaust but the car wouldn't run at all well like that?
It may be worth taking the plugs out and compare front to rear, but really this is very odd?

Alec