How much RPM drop from park to drive with stock type 340 convertor
1) What is 'transfer slot sync' ?
2) Is it the 'off idle' circuit - idle air bleed ?
3) How does drilling holes in the primary throttle plates work ?
As to #3; Yur getting ahead of yourself, that cam may not need any additional bypass air to what the PCV will supply.
As for #2; no, none of those
As for #1; if you have a Holley, remove the carb, drain it and flip it over. Look into the primary throttle bores up where the mixture screws are. Close by, you will see a couple of vertical slits. These are your transfer slots. These are your main fuel supply for low-speed operation. The mixture screws are basically just idle enricheners. But if your throttle blades are not in the right place on the transfers, at idle, you can make it idle with the trimmers, but as soon as you open the throttle, the mixture is wrong, and so the engine complains about it right away.
At idle, your engine will like lots and lots of advance, maybe mid 20s to even 30s. To see this, just tug on your Vcan until the rpm peaks, then read the timing.
But you can't set it there with a non-computerized timing, vehicle, because the Power-timing will be all wrong, and the thing will likely detonate itself to death.
So, I usually recommend the transfer slot exposure, underneath the blades, with the throttle on the curb-idle screw; be adjusted to a lil taller than wide. In your case with a more or less stock engine, Ima thinking closer to square will do it; but it's just a best guess. We can figure that out later; the engine will tell us as we go along.
Now, when you put this carb back on, the idle-speed is apt to be way too fast, and to slow it down, you will have to reduce the timing.
Once the T-slot exposure is set, Do NOT Mess with it. Use the timing to change the idle rpm.
Don't even look at the timing, just push the Vcan back until yur speed is in the ballpark. Mattax likes 750 in N/P, which is a good number, but I like 600/650 in gear. We'll let the engine tell us what it wants as the tune progresses.
OK here is the theory;
By retarding the idle-timing, we are reducing idle power, which with a fixed throttle blade, stabilizes the airspeed past the transfer slots. Now you an use the trimmers to compensate for the airspeed loss when you put it into gear. If your trimmers get out of range, either too far open or too far closed,
THEN, we will change the transfer slot flow, to get the trimmers back into a working range.
If it should come about that we cannot get into range
Then, we will have to find air elsewhere, which we will call idle-air bypass.
I had a 4-speed type cam in my 360; a Hughes HE2430AL. the specs were 270/276/110, and 223/
[email protected]. I put a Holley 750DP on it and it required NO idle air bypass.
Your engine may vary,lol.
