Hello I’m running a 6x2 multi carb set up on my engine Chevy 350 I got matching Holley 94s. I need help on what power valve size I should start off with as a base line currently thinking of putting 2.5 HG power valves and .047 jets. What are you guys running or what would you recommend? Any information helps thank you all for the help
Too generic to answer. Need some more info: What intake manifold? Are you running all six carbs? How are the carbs configured? Do all have idle circuits? Straight or progressive linkage? What camshaft?
The intake is some what a log manifold set up that I casted will have three carbs for one side of the engine and three for the other. I will be running all 6. I read online that the center carb should have the idle circuit and the outer two should not but then I read other post where people have idle circuits on all of them. I will have progressive links. The cam is 212/22X, .552/.552, 107 LSA
OK. What follows is my opinion based on my experience. I do not profess to be an authority, expert, or anything of the like. I will start by saying that almost any engine will put out more useful power with a decent intake and a four barrel carb than most multi-carb setups. I accept that, but I love the look and challenge of the multi-card setups. Especially the 6X2s. But they are absolutely NOT a set it and forget it proposition. You need to like pulling carbs apart and changing stuff until you find the elusive sweet spot. You need a well thought out fuel pressure management system that will give you consistent pressure that does not exceed 3 lbs. The typical major hurdle is getting enough air flow velocity through the carbs so they meter correctly. This is influenced by manifold design and camshaft selection impact on manifold vacuum. In some cases it can be improved by carb spacers. In your case perhaps the vacuum loss by that tight LSA will be helped by the short duration. I prefer keeping idle circuits in all of the carbs. It's sometimes hard to get perfectly sealed throttle plates. It provides some tuning flexibility if needed. If everything is tight, just turn in the adjustment screws and don't use them. I typically have the slightly open to smooth things out. It also gives you the option of which carb positions do what: two center primaries and dump the ends; four outter primaries and dump the centers; etc. Myself I prefer straight linkage vs. progressive. I just find it easier to tune and keep adjusted. My typical 6X2 starting point is two center carbs jetted two numbers above the other four. Center carbs have power valves and the outter four do not. All carbs start with same accelerator pump setting. Straight linkage. You won't know the correct power valves number until you get to drive the car and know your part throttle cruise manifold vaccuum. A uni-sync and a vacuum gauge are basic required tools. If you have some type of AFR meter that's a plus, but you can manage without. I think your numbers that you listed are not a bad starting place since it's pretty much a guess until you get some actual vacuum numbers and see exactly what type of idle manners the engine has. Good luck. I am sure there will be some frustrations, but just keep at it.
Thank you for the knowledge jmountainjr I greatly appreciate you sharing this information with me. I know it’s going to be a long learning curve to get the right setting down but it will be worth it can’t beat the look of a 6x2
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