When one carb cuts out...

[Boink]

Just a curiosity question from a friend with a dual HS2 set-up (like mine - so I'm curious but am unwilling to "test" it). If one carb cuts completely out (even for a few seconds), what might one expect in performance? Would there be a massive loss of power? A sputtering decrease of performance? Would pushing on the accelerator do anything to compensate? I'm curious too.
Asked another way, if you were cruising at, say, 40mph and one carb ran dry or stopped its flow, how would an A-series behave? I realize that the intake manifold wouldn't be optimal for a lop-sided carb set-up, but, still, what would one expect?
Inquiring minds want to know.
Thanks.

 

[JPSmit]

I presume it would behave like it was running on 2 cylinders, ie. massive loss of power, I don't believe you there is any opportunity for even the slightest bleed over of mixture from front to back or back to front is there?

 

[dklawson]

I would describe it as a sudden and severe loss of power. The car will idle but is hard or impossible to rev and the car will be difficult to drive as the throttle will let in the same air with much less fuel.

I have experienced this a few times when the float valve would stick closed on one carb but not the other.

 

[Boink]

Thanks guys. Yes, I figured that drafting to the other 2 cylinders would be severely compromised (given a standard intake manifold). Hadn't really thought that, yes, there would be twice as much air (what with the non-functioning one letting in the same amount).

Related curiosity question. In such a situation, would there be a substantial increase in oil pressure?

 

[JPSmit]

Shouldn't affect oil pressure at all as oil pump spins with the engine so, it might go down if revs drop but not up. Sounds like you are trying to diagnose something. What syptoms were there?

 

[Boink]

Thanks. No, actually, I'm fine.

The other set-up I was referring to had a major loss of power as if a carb was cutting out... but then it would catch and come back. High speed (over, say, 50) wasn't possible without some sputtering. Can't help but wonder if there is a float-bowl difficulty and/or clogged line at a carb (since the fuel-pump is producing a good flow). Interestingly, there is never a problem when not under load. Carbs are allegedly rebuilt. Owner is flummoxed.

As I understand it, car drives pretty good but on load at about 40mph will suddently start to cut out with a major loss of power. After a pause (and some letting off acceleration), power is back - sometimes back suddenly. Again, never a problem going, say, down-hill. High speed (over 50) not possible without some sputter.

When it was "over-driven" in this state there was oil blown out of the oil separator. But I don't know much about that part.

I figure that maybe one carb is misbehaving in an intermiitant way. As I understand it, electrical system is fine.

 

[Billm]

Sounds like the tank has crud in it and pieces are covering the inlet in the tank when there is a long continuous draw (easy to simulate if you pump a gallon or two into a bucket in the garage)
--or--
a piece of crud is blocking one of the carbs on hard draw (during high speed running)
BillM

 

[Boink]

Sounds like the tank has crud in it and pieces are covering the inlet in the tank when there is a long continuous draw (easy to simulate if you pump a gallon or two into a bucket in the garage)
--or--
a piece of crud is blocking one of the carbs on hard draw (during high speed running)
BillM

Makes sense. As I understand it, the flow at the first carb (out of the filter) was good. Might be wise to check at the second one. Thanks!

 

[JPSmit]

Sounds like the tank has crud in it and pieces are covering the inlet in the tank when there is a long continuous draw (easy to simulate if you pump a gallon or two into a bucket in the garage)
--or--
a piece of crud is blocking one of the carbs on hard draw (during high speed running)
BillM

Makes sense. As I understand it, the flow at the first carb (out of the filter) was good. Might be wise to check at the second one. Thanks!

may also be as simple as needing oil in the dashpot. Mine stumbled badly accelerating but then was OK at cruise. First the oil was too light, then discovered the oil needs to be replenished.