bulldogSS

So I recently swapped to a 600HP. First I set timing to 12 initial and 36 all in at 2500 rpms. Vac advance hooked to manifold vacuum and limited to 11-14 so I'm seeing 25 at idle( streetfire dizzy with no vac adjustment only limiting plate) Next I moved on to the carb. It came with 70 jets and 6.5 pvs front and rear. I am now at 66 jets and 9.5 pv on the primary. Have not touched the secondary side yet. When I put the carb on I set the transition slot to look like a square and closed the secondary blades. After hooking up vacuum gauge and adjusting mixture screws I am wondering if my set up is correct. I am currently at only half a turn out from closed on all four idle mixture screws and had to close the primary blades a touch to get idle down. So now my transition slot is prob just barely uncovered if even at all able to be seen from underneath. All the carb tuning was done with vacuum advance unhooked. Any input would be great. Thanks

sofakingdom

iTrader: (1)

If it RUNS good, it IS good.

No matter what you changed, no matter what the new part numbers are, no matter what the guys in the McDonalds parking lot say, no matter no matter no matter.

Everything you describe sounds completely normal.

bulldogSS

Thanks for the reply I was hoping you would chime in. After reading the sticky I was concerned about the transition slots being covered more than spec and the mixture screws only being half a turn out. But I guess 4 screws half a turn out may be the same as 2 screws a full turn out?? Also I wasn't sure about advance at idle with manifold vacuum. How much is to much? Again thanks

sofakingdom

iTrader: (1)

Having the throttle blades more closed than "normal" (transition slots as you describe) is typical with a relatively HP designed carb (i.e. one that was built expecting to be installed on a motor that struggles to idle, specifically from a very long-duration cam)) installed on an engine that has no trouble idling (specifically, one with a relatively more like stock cam). As long as it doesn't have the problem where there's NO transition AT ALL as you tip-in the throttle off idle, it's fine.

Same deal with the 4-corner idle. It's meant for race motors, not streetable ones. While it "works" fine on street motors, the extra fuel it can deliver is unnecessary in such a situation, which is why you have to turn the screws in so much. Doesn't matter; all that matters is, how many fuel molecules reach the intake stream per air molecule. As long as that ratio is correct, and the rest of the systems of the carb are working correctly at the same time, then the screw setging just is whatever it is, and that's all there is to it.

As far as "too much" vacuum advance, the only time you have "too much", is if it runs better with less. Remember, if it RUNS good, it IS good. THE ENGINE knows far better than anything or anybody else how much timing is ideal for it. It will tell you in no uncertain terms when a change that you make is to its liking or not. If it keeps running better as you make some particular incremental change, keep making that same change in the same direction until "optimum" is reached and you begin to run worse on the other side of "ideal", then go back until you reach the point where no further improvement can be made. Doesn't matter what the "number" is, doesn't matter what "they" say, doesn't matter doesn't matter doesn't matter doesn't matter. There are only 2 possible states for a tuning adjustment to be in: either it's already the best it can be (quite rare I assure you), or you still have work to do.

"Runs good" is somewhat subjective. You have to decide what's important to YOU, since all of this stuff is to some extent a bag of compromises. Improve one thing, some other thing might suffer. "Best" is up to YOU to decide, for YOUR car the way YOU drive it in the place YOU live on the roads/tracks YOU drive it on with the fuel YOU buy etc. etc. etc. Typically this would involve some combination of snappy throttle response, good gas mileage, consistent idle, low running temp, easy starting, freedom from pinging, and maybe a few other factors as well.

Sounds to me like you're on the right track. Trust your own judgment and powers of observation, don't allow yourself to be sidetracked by the herd mentality.