Re: 37, 120 carb percolation problems

Posted by PackardV8 On 2012/8/1 14:28:31

Looking at the S'berg schematic i see what appears to be a BOWL VENT. i.e. No such mechanical anit-perc valve. The vent is located in the air horn of the carb. It is a verticle channel on the INside wall of the airhorn and nearest the bowl.

There also appears to be somekind of a cast-in 45 degree baffle very near the top of the airhorn of the carb that subteds with the vent passage.

Be sure that this passage is not blocked either by dirt or a mis-cut gasket between airhorn and carb body.

Note that any high speed or low speed passages thru the carb such as the air bleeds, IF blocked or plugged, would cause either low speed or high speed performance problems, extremely poor fuel mileage. Syphoning is not likely to take place at engine stopped only status but also would happen when ever bowl is ful eve nwhile running. So i doubt the problem is due to any plugged passages OTHER THAN the bowl vent. During the mid-70's (dawn of oil crisis) to present there were often shade trees that would plug such vents in ANY carb. Sometimes plug them by cutting gaskets with no provision to allow venting.

Setting the float level lower is a good idea too unless you're running very high sustained engine rpm under heavy load conditions.