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Pro 2 Carb rules

Broncomania

New Member
An e mail was sent to me inadvertently the other day by a Pro 2 driver.Lost the e-mail.It was about running hoses from carb vents to back of truck.His engine sponsor was concerned about tuning issues.Carb vents primary purpose are to provide atmospheric balance in float bowls.mods like this could have catastrophic effect on engine.
 

GEARDOC

Well-Known Member
Engine unlikely to run without atmospheric signal
 

Broncomania

New Member
Sorry I wasn't clear on my post Geardoc.Your right it will not run without atmospheric pressure pushing fuel from bowls through jets.The vents were moved inside the air horn by factory engineers to compensate for the air filters slowly plunging up.This helped keep mixtures correct over time.Remember they didn't have oxygen sensors and the like back then.Apparently the rules people want hoses running from these vents to rear of truck.There are many implications with this including fuel sloshing into tube and laying in a low spot blocking signal.No fuel flow would result.Wind blowing over end of tube or vent filter could cause vacuum.Same result.
 

gawdodirt

Well-Known Member
They were moved in the air filter to keep dirt out of the float bowl. And it was logical for manufacturing. When the filter plugs up, the AFR goes rich anyway as the "compensation" is being made in a vacuum. So no, it doesn't compensate for lack of air. Marine style vents may be what they're looking for.

GD
 
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