AVS 650 hesitation
AJ's guide to Transfer Port Synchronization
To set the idle fueling; such that the carb does not hesitate on gentle tip-in, you gotta
balance the fuel delivered from the primary low-speed fuel delivery circuit, namely; the transfer slots, TO; the idle mixture trimmers, namely the idle discharge ports.
When you do this, you will find that, to get it right, there is a very small window of adjustment on the transfers . And in most cases, a street cam will idle too fast with the timing all your friends will tell you, has to be like as much as possible until the starter kicks back. But that is not true!
The engine will tell you what it wants for idle-timing; if you just listen to the clues. You should not force what is, IMO, massive amounts of idle-timing on your engine. Below the stallspeed, it simply does not matter. I have run the same ancient Holley 750DP on a 292 cam as on a 270 cam, in the same engine. The only change to the idle circuit, was to the bypass-air.
Now, if the stumble occurs later, after the carb gets up on the mains, lots of good advice has been given.
Never underestimate timing;
Your engine has exactly ONE timing requirement which is to get the max cylinder pressure delivered to the crank at very nearly just one time,in degrees,which is in the neighborhood of 25 to 28 degrees ATDC. Your job is to start the fire,at the right time, under all conditions, to make that happen.
To break it down, your engine has these timing requirements;
A) Idle-timing
B) Power-timing
C) stall-timing
D) Part Throttle timing, and
E) cruise timing.
ok , I'll include; for manual trans cars
F) closed throttle decel-timing, and
G) low roadspeed timing
Of all of these;
Power-Timing is the most important and also the easiest to figure out.
Idle-timing is a little more involved.but
Part Throttle is the toughie.
And cruise-timing will surprise the heck out of you.
Stall timing is often whatever comes out in the wash, but that is not right! Timing at stall is what you are forever gonna be feeling, every time you mash the pedal. Too much and the engine will detonate. Too little and the engine will be lazy. Stall timing to power-timing is where you are gonna spend most of your time in tuning,and where brain is gonna get it's exercise.
Bed time/ I'm passing out while typing!
