383 Wont Idle with new to me 800cfm DP. Idles and runs ok with Edelbrock/AFB
Timing on this distributor is all in by 2000. After experimenting with this carb the other day, the Edelbrock was put back on and it went back to running smooth. I am a little limited on what I can run on total advance because of high compression ratio and pump gas. I run av gas or an av gas pump gas blend when I plan to race it or do spirited driving. Currently it is on pump gas 91 octane is best at pump I can buy here in California.
Waitaminute.
If this is a track-car, ignore the following;
How much cylinder pressure is this engine making?
With a true 10.5 Scr and that cam's (if a 108LSA cam) Ica of 70* installed at 104*, then yes; you have too much pressure for iron heads. If a streeter I would knock it down and fix that. But just putting 10.5 pistons in the block, doesn't automatically make it a 10.5 engine. Ima guessing you know that.
But if a streeter, check this out. This has nothing to do with your problem, just an observation.
I see your AV gas solution as
maybe a band-aid for the 33* at 2000 rpm. If this is a streeter with anything but a very hi-stall TC, there is no reason to run that much low-rpm advance.
I have run that 292/292/108 in my 11.3Scr Eddie headed 367 with as little as 5* initial timing, but mostly with 14* initial, and with 28*@2800, and 32@ 3400. That's all on the same curve. And with the Vcan modded to 22* maximum, the total Part-Throttle timing available was; 50*@2800/54*@3400. And it was a tire-fryer on the power curve. Tuned like this it has always run on 87E10 all the time, and at up to and even a tic over 185 psi cylinder pressure.
As a streeter;You gotta have a working Vcan..... you just gotta.
As a streeter, ask yourself how often do you go thru the zone of STALL to 3400 at WOT, compared to how much time you spend at part throttle. Then ask yourself why you have a race timing-curve and a no-Vcan distributor in your streeter. With say a 2800TC, then 2800 to 3400 is a one-time deal from around 23 mph to 28mph, surely your 388 cuber can pull you thru that zone with less timing..... and therefore with less antiknock.
Right now,
at 33* all-in by 2000 rpm, and no Vcan;
below about 3600 rpm, your timing is right just about exactly at one rpm and load setting, and Ima thinking it would be at very light acceleration around the stall-speed.And again at maybe 3200WOT....At over 3600 it's never right.
And neither is it right at idle. And this is very important.
With 33*at 2000, and maybe 10* in the mechanical, this makes the idle timing to be around 23*, am I close? But it won't hold still because it wants to be advancing all the time with those very light springs in there. If you can't get the idle down under the start-point of the timing curve, then you will never have a stable idle-speed.
But it gets worse, with the timing so far advanced then when you try to idle it down, you will be closing the throttle to below the start-point of the transfers, shutting them off, and then it stalls.But if some transfer exposure still exists; then,now with the low vacuum of that cam the transfers may want to dry up. So when you get to opening the throttle, it takes time for the transfers to wake up, and so you get a big old stumble. To cure that you start fudging the pumpshot and fuel level, and on and on it goes. While the cure is staring right at you; namely a lack of transfer slot exposure, mostly caused by the excessive idle-timing.
So check it out.
IMO, it runs pretty good (with the Edelbrock carb) because it's a 388 cuber often running with extra anti-knock.
Imagine how it could run with the proper timing at least some of the time.
Please don't hate me..... I'm just trying to help