That's a big cam.
You HAVE to set the Transfer port exposure under the throttle blades just right.
To ballpark yours; Set the T-port exposure to a little taller than wide, but not 50% taller! maybe 20 to 30%, and leave it alone. Set the idlespeed with timing; ~14* with a manual trans, or ~18* with an auto. Defeat the vacuum timing. Put a known good 10.5PV in there, or a PV-plug, and a known to be working PCV.
That leaves just bypass air to fool with. I like thru-holes, others like secondary cracking. After you get it set nice, don't forget to re-install the PV.
A little explanation.Properly set;
At idle your engine is idling on the low-speed circuit which is the Transfer slots. But at idle there is not quite enough mixture coming thru there, so Holley gave us two small additional trimmer holes.
Getting this this carb to work with a big cam is a delicate balancing act between those two discharge ports and getting the timing right. All three have to be co-ordinated.
You start with setting the trimmers (Idle-mixture screws) to the center of their adjustment range. Then setting the Transfer slot exposure, then throwing a bunch of idle timing at it until it runs. At idle the engine will easily take 20 to 30 degrees.....or more, don't worry about it.
After it warms up, you take timing out of it to get the idle-rpm close to some arbitrary target you pull out of a hat; I like 800 with that cam and my manual trans.. With a big cam, very soon idle quality will begin to suffer, and you will be tempted to start turning on screws. This is the wrong thing to do.
Now,
>cracking the secondaries introduces dry air into plenum, which in my case, caused the rearmost cylinders to run lean, and the exhaust caused my eyes to water.
>1/8 holes in the primaries is too much; the transfer ports will be closed too far and run lean, So then in compensation the mixture screws have to be opened up, maybe as far as they go. This makes the idle speed too high, so you have to back off the timing. It's messed up.
> idle runaway occurs for a number of reasons that I can think of;
1) the mechanical timing is unstable; or
2) the V-can is being tickled at the sparkport because the throttles are too far opened; or
3) the carb is vacillating between the T-port supply and the trimmer supply; or
4) the PV circuit is dribbling thru a ruptured diaphragm; or
5) the fuel-level is unstable ;
basically it all comes down to a tuning issue.
The big-cammed engine wants extra air only; not air-fuel mixture. Here is one method I have used to determine how much extra air she wants;
Grab the PCV line, (which should be connected to the carb port at the front of the carb and dumping into the same airstream as is passing by the transfer slots; NOT connected to an intake runner,) and pull the PCV out of it, but get your thumb over the hole pronto before she stalls. Then slide your thumb over to expose some hole. Notice the idle quality gets better, and she gets an increase in rpm.. Find the optimum hole size for idle quality, and then if the idle-speed gets too high,then retard the timing some. Repeat as often as necessary, until you have the timing down to a reasonable number (14* for a stick, and maybe 18/20 for an automatic); while simultaneously getting down to 750/800 rpm. Fiddle with the hole size under your thumb for best quality.
Now,without moving your thumb; yank that hose off the port and shut off the engine.Ok now the hole size you have exposed is the correct size for this combo. Your job is to translate it somehow into the carb and PCV system.
So calculate the area of that exposure and divide it by 4. The PCV will take 1/4, and each primary throttle valve will take 1/4, and that leaves 1/4 for fine-tuning; this is your starting point.
By field tests, I came up with the 2 of 3/32 holes.
After you get this base-lined, THEN you can fine tune the T-Slot exposure to trimmer adjustment.
Here's how I do that;
If you find the trimmers like to be screwed too far from the midpoint, then change the "curb-idle adjustment" say 1/4 turn atta time, and put the trimmers back to mid position . Repeat as necessary.
The timing has to be stable. I choose springs that keep the timing stable to at least 200rpm over the target.
If your exhaust is still watering your eyes, your hole size is probably too large or the timing is not enough.
Here's how you know when the t-slot and trimmers are set right; just retard the timing until the engine stalls. If it keeps on running down to 600 rpm or 5*advance before it stalls, you got her close to perfect. Start it up and put the timing back.
In year 2000, I had almost that exact combo;367 cubes at 11.3Scr, with aluminum Eddies, and the 292/292/108 cam; but with an AirGap and Holley 750DP.
I closed up the secondaries tight, and drilled holes in the primaries to give the engine the air it was craving. I started with 18* idle-timing, about 800 idle-rpm, and 2 of 1/16" holes, one in each blade. I run a jobber,factory 318 PCV.
My car has a manual trans and with this tune the power pulses at low speed were so strong the car would start bucking to the point I had to de-clutch.
So I decreased the Idle-timing to 16 then 14. And the idle-speed went down too low. So I drilled those holes a bit bigger, I think I ended up at 1/8" which turned out to be too big. So I soldered those holes closed, moved over and drilled 3/32" holes.
At 14*advance and the transfer exposure set a little taller than wide, the idle came in at 750rpm with vacuum between 10 and 9. With that cam, I ran a 10.5PV and IIRC 72/78 jets. The idle vacuum will depend on the installed centerline, and your altitude; I am at 930ft.
That cam is long gone; it was just too big for me.
Transfer Port exposure will be very important.