To no one in particular, but to everyone hating modern gas; I just gotta say ;
You should try Canadian 87E10, which works fantastic in my 11/1, alloy-headed, 367. No troubles whatsoever. not even cruising 65=2240 rpm in overdrive, with the throttles nearly closed.
IMO
if you get carbon on the seats; that ain't from the quality of your gas. and I would almost bet it points straight back to NOT having the Transfers synced properly to the mixture screws, and thus running rich, like 90% of the time.
Now I know that most of you swear by 18* or more, of idle timing, and I get why. I tried it too. But I'll bet nearly every one of you who do that, have so-called carb issues like running rich off idle, and at cruising, and whenever the carb is running on that circuit.
And the proof is this;
What are your mixture screws set at?
With a Holley, I have always had success at 1/2>3/4 turn out, and
With a Carter, 2>2.5 turns out.
This, with cams from 268 to 292 advertised; any cam in that window.
If you clean up your idle, you won't have carbon issues;
and your copper plugs will last 100,000 or more miles, like mine do; and just maybe you can squeeze some decent cruise-fuel-economy out of your modest-cammed hotrod SBM.
I don't know how many times, probably dozens of times, that I have said this; clean up your idle. Quit trying to run idle/low speed timings that the engine doesn't need nor want, and give it some decent cylinder pressure, which is what it really wants.
As for idle timing;
> sync up the transfers, and the engine will tell you what timing it wants by the idle-speed it gives back to you.
> Then fix your timing curve to give the engine what it wants, at stall speed; and not what it can stand .
> Power-timing, unless you have too much cylinder pressure, is always gonna fall into a tight window of 34 to 36 degrees, 37 at most, which is mostly chamber; shape/temperature/and pressure, dependent.
AND
on the street, with an SBM/auto-trans, normally aspirated combo, at WOT; I challenge any of you to feel the difference between optimum timing and 2/maybe 3 degrees retarded. You cannot and here's why;
1) yur gonna burn thru first gear so fast, the engine is never gonna be loaded, so who cares about a few hp this way or that; and
2) 50 mph in second; even with 3.91s is gonna choke the rpm down to no more than 3900, and the load due to wind-resistance is only just barely being addressed.. The engine won't hit 5000 until 64mph, and again, wind resistance is just hitting the engine; are you gonna feel 3hp or 5 or 7? Be truthful;
7/350 @5000= 2%
5/250 @3900= 2%
Yur never gonna know.
But yur sure as heck gonna rag on bad gas carboning up your valves.
Do you know the optimum timing of your engine at 3900? I'll bet not 5% of you do. But you all want to run 37 degrees right? Cuz you heard somebody say 37 is where it's at... right.
And so, to get 37, you might have to run 18 at idle, cuz you don't know how to fix your timing curve. And so you compromise say 90% of your Part Throttle power curve, to get the last 3 horsepower at 5000, where you almost never go, under full load.
And in the meantime, 18* messes up your T-slot sync, which leads to rich running, which leads to carbon fowling your entire intake tract, beginning two or more inches up into the intake manifold, and ending at the very end of your tailpipes, and a muffler crammed full of carbon.
Here's me;
