I have a 350 blower motor with mild to radical cam. It had two carter afbs 500 that were a little too small. I just bought 2 brand new holley HP doublepumper blower/supercharger carbs. Series 4150, Holley # 80575 (2)600 CFM carbs These are boost referenced. I plumbed the new vacuum to the carb boost refenced (4) tubes sticking out of the carb bodies. It fired right up. It idles extremely fast at around 2800 rpm. No linkage is hooked at the moment and both (primary and secondary) idle screws are backed all the way out on both carbs. The (8) mixture screws are 2 turns out each. I do not think there are any vac leaks as everything is new, tight and torqued. Please give me advice as to what to do next. Help I need it to idle!
Hi, You probably need to close up the secondaries on both carbs. I put a 750 HP on my 400 and couldn't get it to idle until I removed it and adjusted the secondaries closed. HP's are set up as race carbs and want to idle fast although it sounds like you may have more of a vacuum leak than just the secondaries. Rick
Might want to pull a carb and look at the base plate, make sure there aren't any p***ages that could be leaking air in with the gasket you are using. or unplugged vacuum holes. 2 turns out? maybe the new ones work different, the older ones like about 3/4 turn each I wonder if there's something in the vacuum reference circuit you have to plug if you use the external reference? I don't know anything about the carbs you have...just a guess.....I get by with the old 4777s on my blower motor.
Well, I could be wrong but my understanding of a boost referenced carb is for the PV. If you dont connect a manifold line to the carbs, the power valve will see ambient air pressure always and will never have vacuum to close the power valves. But again- I could be wrong. When I ran blowers, I didn't run carbs.
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