Gary Lewis Posted August 7, 2018 Share Posted August 7, 2018 Mercy sakes alive it's HOT down here in the Gee... fortunately I had a spare PV 6.5 whatever that means. No remote vacuum on this one so I'll change it and check back in shortly. 105 heat index yikes! 79 degrees here in 'took. And a t-storm. 6.5 is the point in inches of vacuum where the power valve opens. Above 6.5" it is closed, but below that it'll be enriching the mix for power. Link to comment Share on other sites More sharing options...
JMUBullnose Posted August 8, 2018 Share Posted August 8, 2018 Interesting - I have potentially blown PV on my trouble shooting list as well for the 2150. I worked on the truck over the weekend and haven't driven it since Sunday. Last two days as it sat in the driveway I would occasionally get whiffs of fuel when walking by it while working in garage or in yard. No puddles under the PV that I could spot but that could also help explain some of my hard start issues as well. Link to comment Share on other sites More sharing options...
Gary Lewis Posted August 8, 2018 Share Posted August 8, 2018 Interesting - I have potentially blown PV on my trouble shooting list as well for the 2150. I worked on the truck over the weekend and haven't driven it since Sunday. Last two days as it sat in the driveway I would occasionally get whiffs of fuel when walking by it while working in garage or in yard. No puddles under the PV that I could spot but that could also help explain some of my hard start issues as well. PV's, and fabric accelerator pumps, are the achilles heel of Holley or Holley-type carbs, and the 2150 is one of those. The original design was flawed as it allowed manifold vacuum or pressure to get directly to the power valve such that a backfire through the carb would frequently blow the PV. A fix for that error was finally applied to new Holley carbs as of 1992 and is available for retrofit to the bulk of carbs that don't have it. But I don't think it was ever applied to the 2100 or 2150 as they were out of production by '92. Sitting at the bottom of the bowl, as the PV does, when the fabric is blown two things happen. First, when the engine is running the vacuum usually can't overcome the spring and the valve stays open. At first blush that would seem like it just causes the mix to be rich by however much fuel can flow through the PV's orifice(s). But, the second thing is that there is now a direct path from the bowl of the carb, through the power valve & its diaphram, and into the intake. So, when the engine is running gas is being pulled directly into the intake. And when the engine is off gas runs out of the bowl into the intake and the bowl is dry when you try to re-start the engine. Link to comment Share on other sites More sharing options...
BeagleRock Posted August 11, 2018 Author Share Posted August 11, 2018 PV's, and fabric accelerator pumps, are the achilles heel of Holley or Holley-type carbs, and the 2150 is one of those. The original design was flawed as it allowed manifold vacuum or pressure to get directly to the power valve such that a backfire through the carb would frequently blow the PV. A fix for that error was finally applied to new Holley carbs as of 1992 and is available for retrofit to the bulk of carbs that don't have it. But I don't think it was ever applied to the 2100 or 2150 as they were out of production by '92. Sitting at the bottom of the bowl, as the PV does, when the fabric is blown two things happen. First, when the engine is running the vacuum usually can't overcome the spring and the valve stays open. At first blush that would seem like it just causes the mix to be rich by however much fuel can flow through the PV's orifice(s). But, the second thing is that there is now a direct path from the bowl of the carb, through the power valve & its diaphram, and into the intake. So, when the engine is running gas is being pulled directly into the intake. And when the engine is off gas runs out of the bowl into the intake and the bowl is dry when you try to re-start the engine. Very in depth explanation, I appreciate it and need all the help I can get. Heading to my old Hometown of Webbers Falls tomorrow to work on a lawnmower, something I KNOW about lol. I hope the Bluebird of Happiness gets me there and back safely! Link to comment Share on other sites More sharing options...
BeagleRock Posted August 11, 2018 Author Share Posted August 11, 2018 Interesting - I have potentially blown PV on my trouble shooting list as well for the 2150. I worked on the truck over the weekend and haven't driven it since Sunday. Last two days as it sat in the driveway I would occasionally get whiffs of fuel when walking by it while working in garage or in yard. No puddles under the PV that I could spot but that could also help explain some of my hard start issues as well. Join the dry bowl syndrome club 😉 Link to comment Share on other sites More sharing options...
Gary Lewis Posted August 11, 2018 Share Posted August 11, 2018 Join the dry bowl syndrome club 😉 Good luck! Link to comment Share on other sites More sharing options...
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