I would also consider getting a quick change vacuum secondary kit so you can tailor the opening rate of the vacuum operated secondaries simply by pulling the cover and putting in a heavier or lighter spring.
At this point you might need a heavier spring to delay the opening.
As far as your vacuum advance goes, you can try either way. I have noticed some engines like full vacuum hooked up and others like timed vacuum. Try setting your base timing around 12* BTDC and hooking the advance up both ways to see which runs better for you. No matter which way you end up going, always set the base timing with the vacuum unhooked. Then hook up your vacuum line and adjust idle speed to what you want. BTW what are your cam specs and such? Depending on the combo it may like more base timing, which usually happens with larger cams.
Also I believe the stock jets in a 3310 are 72 primary and 76 secondary. Being that the plugs are that black I would try a 68 in the front and maybe put your 72 in the back. Then you would only be buying one set of jets to see if this moves you in the right direction.
Thanks everyone for the replies! I'm very anxious to get at this now. Being 25 I've been spoiled by EFI my whole life and am looking forward to learning about carbs.What is the best order of doing these things? If I had to guess I would say set timing, check vacuum at manifold to figure out correct power valve size, change jet w/o changing power valve, use vacuum gauge to set idle mixture screws, change plugs and drive? Does this sound like a reasonable order?
With engine at operating temp, hook up vacuum gauge, and put it in gear. Whatever that vacuum reading is, split it in half for your power valve size. The 68 jet size recommendation sounds like a good starting point. I'd change the spark plugs for sure after jet and power valve change. I always run my HEI on the timed port. They always had a slight miss at idle when I tried full vacuum. I do know a few guys that run them that way. Power valve selection is key with a cammed street engine for off idle acceleration.
I would start by setting the timing. As others have said, the performance cam will likely want more timing than the stock spec. Give it a few more degrees to start. In the end you want as much advance as the engine can tolerate without detonation. Try setting the base timing to achieve best manifold vacuum at idle and adjust curb idle speed as you go. Next set the idle mixture screws to acheive best manifold vacuum. See how it runs. Next I would confirm what jets are in the carb and would re-jet it to the recommendation from crotchss (68/72). Then I would double check timing, idle speed, and idle mixture adjustments and see how it runs. I might put a new set of plugs in it at that point and drive it some and then read the plugs. If it still has the hesitation, I would look at power valve selection. Once the hesitation is cured I would move on to fine tuning the spring in the vacuum actuator for the secondaries, the advance curve, timed or ported vacuum for the advance, etc. Try to do one thing at a time so you can gage the effect.
So I took the float bowl and metering block off to see what jets and power valve I have. The jets in front are two number 69 and the power valve is 4.5. I don't have a metering block on the secondary side of the carb meaning there wouldn't be jets correct? I'm going to leave the power valve alone for now and switch the jets to a 65. When Im done with work im going to put the new jets in set idle to vacuum and hope I can get it timed correctly. I will update tonight with what I find out. I also attached a picture of the paperwork I have for my cam. I don't know what any of it means.
Yeah, I forgot the 3310 uses a metering plate in the back, the fuel orifice is equivalent to a 76 jet. You can change it out to a metering block and jets, but you will have to lengthen the fuel line slightly. In my opinion it is a great upgrade to do to add more adjustability. The secondary jet isn't adding fuel at cruise or light throttle, just when you're "getting on it". Looking at the cam sheet, it's a fairly healthy cam for a 350 street motor. I'm not saying it's too much, because I've run just as much and more in a daily driver before, but I personally think I would run at least a 2200-2600 converter. The engine will like it a lot more getting into its power band much quicker, also won't be so doggy down low.
Saying that, I still think the jetting on the primary side will need taken down like you are doing, getting the idle mix set first is a must like you say and the right timing.
In case you didn't know there are Holley jet sizes that are different numbers but still use the same drill size, I don't think this will affect you in the range you will be working in but I have seen people go down 2 jet sizes and notice no difference since the only thing that actually changed was the number on the jet.
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