I've read many of the past threads and all have great information. I have tried a few things and had some success already but I really want to get my engine idling perfect with excellent driveability. I refuse to settle for just good. Problem is I am only a mediocre carb guy so I could use some pro advice.
I had my 383 running great with a 3310 Holley. When I put my ram charger airbox and air cleaner set up back on, I was forced to go back to the lower profile iron intake and original style Holley carb. Not sure on CFM but it is no doubt smaller than the 750 I had. The carb is perfectly rebuilt but I am not able to get it as smooth as the 3310 I had. I am thinking the older carb has limitations an cannot overcome the hot cam I am using.
When setting idle speed, in order to get the proper idle speed, the blades were open pretty far and it uncovered the transition slot. Idled perfect but as soon as you tipped the throttle just a hair, it would go lean and die. Stabbing it was the only way to overcome the off idel stumble. Not only this, I found I had to open the idle mixture screws to 4 1/2 turns to get it right. I knew something wasn't right.
Next, I adjusted the stop screw on the secondary blade (the one accesible only from the bottom side). By opening up the secondarys (which were completely closed), I was able to close the primary side a bit and this helped alot. I found that the more I opened the secondarys, the more I could close the primary side. The transition slot was no longer wide open and I also found the idle mixtues screws could come back in.
The problem I found now was there seemed to be no perfect balance between the two blades. When the rear blade was open enough to get the front blade in the right spot, I lost the ability to set idle mixture. In fact, the best spot for idle and driveability was when the front blades were nearly closed and the idle mixture screws were completely closed. Another thing I found was that I could not adjust the mixture. By idling more on the back, it seemed a bit too rich. I could open a vacuum line to let in air and the engine speed rose 200 rpm.
So next I tried closing the secondarys a bit but I drilled two small holes in the upper part of the blade to match what the manufacturer did on the primary blades. My thinking was by letting in a little more raw air, it might help balance the fuel mixture a bit. I chose to do it on the secondary side only because the primary side already had two small holes.
What I found was it ran terrible so tomorrow, I will epoxy the new holes back up and try something different.
The only thing I can come up with to try next is to open up the idle feed restrictions in the metering block to richen it up a bit at idle. Then I can close the secondary blade more and try again. Since I originally had to open the idle mixture screws 4 1/2 turns, maybe by opening the idle feed restrictions, I can accomplish the same thing with out using the secondary blade?
By the way, many of these ideas came from Holley books or articles about Holleys.
Any thoughts please? Am I trying to re engineer an old carb to do something it really wasn't designed to do? This carb is clearly not as advanced as the 3310 I removed. I am experimenting on an old Holley replacement style carb the factory used rather than my original from the car so I don't mind drilling.
