Here is my basic setup:
1968 Charger
440 bored 40 over with a balanced 500 inch stroker kit installed
Stock fresh 906 heads.
10.52 static compression. 190 compression across the board when adjusted for my altitude.
edelbrock performer rpm intake
Edelbrock performer cam
Holley 870 street avenger
Stock converter
3.91 sure grip
18 initial timing 34 total
5280 foot altitude here in Denver

last year you guys helped me get rid of a pinging problem because I am right on the edge of getting it to run without pinging on 91 pump gas. My problem that I still have is that I can fuel foul out my plugs real easily if I don't get it to start up right away. I also have to let it completely warm up for 5 or 10 minutes before driving it or will also start to miss a bit and foul the plugs. I'm OK with the warm up period, but not the fouling if it doesn't start right away. Once it is warmed up it runs great, the plugs look good, and the air/fuel ratio is good as well. I am not at all happy with the 870 street avenger and have battled it to get it as good as I can get it, but this fouling is so bad that once it doesn't start it won't start without cleaning or replacing the plugs.

My question is... does 91 pump gas make it hard to start a high compression motor or will it only affect performance?
Thanks for any input.

The engine should still start like normal. Normally I would say your initial timing is probably off, but most engines will start happily at 18.

What are you running for an ignition system? And what spark plugs? Are you running a really cold plug to combat the detonation?

I'm sure you were told last year, but your pinging problem is 10.5:1 compression with (what I assume is) no question.

I have an msd all in one dizzy, Blaster II coil, NGK plugs. I have tried a few different plugs, and swapped out the dizzy and coil.

Have you checked that you are getting good spark at start up?
Do you know what fuel pressure to the carb?
Is that the regular performer cam (204 @ .050) or the RPM cam (238 @ .050)?

Just curious...what's your actual (not corrected) cranking compression?

I have a 500" low deck with 10.5:1 compression, MP 557 cam, MW Eddy heads, Pertronix Ignitor3 distributor, and a ProSystems 950hp carb. It starts, runs, and drives like a new car. I locked out the timing so it's always about 32 degrees, it's a street only car.

Running on the "edge" is never good especially when you cross that edge and the avenger carbs are useless and have swapped a couple out w/ DP`s w/excellent results...............

I hooked one of those in line spark lights on number one cyl and it flashes when cranking, but I did not check exact voltage. Have not checked fuel pressure yet, but it definitely has fuel. It is the regular performer cam, and uncorrected compression is 160 to 163 across the board.

I do have to say that I suspect the avenger carb and am ready to try something else.

Suggestions for a new carb?

Keep in mind that my cam is mild and heads are stock 906. Not sure if/when I will replace heads.

I`ve been modifying many carbs but prefer modern billet ones since the base plates don`t warp(4150)like the alum. ones and the blocks are WAY less porous and easier to drill and tap for my tunes. Even the new carbs are in need of mods to clean up the idle/transition and cruise........

Simple problem..........it if tends to flood easily when it's cold. You have not enough spark, too much fuel, or both. You might also try limiting the mechanical advance in the distributor, so that you can put more initial in it and still have same total.

I have good spark, but too much fuel sometimes. There is a bit of side to side slop on the butterfly shaft and maybe it is exposing varying am out of transfer slots. I'm tired of trying to tune this 870 street avenger. Thinking of getting a quickfuel ss-850. What do you guys think of that carb?

The lower octane rated fuel will burn faster and should be easier to start the eng on. I know in the colder weather in the winter my buddies 68 Cuda thats an 11.5 Indy headed 440 will start easier on the pump then it does on race fuel since the race fuel is slower burning. Course my 63 always starts easy on the 92 pump I run. Ron

Where is your choke indexed?
Vacuum break?

The Avenger carbs are pretty lean in the transition / idle bleeds at this altitude and may need to be adjusted. My carb had an off idle stumble because of this.
If you have changed the jetting and other items to get around the off-idle stumble, then the tune may be too rich.
It also sounds like the choke is not opening correctly?
I guess it is electric choke and not the mechanical?
Are you using a thick carb gasket it spacer between the carb and intake.
On my RPM intake/Avenger combination, the fast idle screw on the carb passenger side would hit the intake unless I used a thick carb gasket.

Not sure what heat range plugs or ignition system you are using. You may need hotter plugs, and a MSD type ignition also helps keep plugs from fowling.

go with the Quickfuel 950

On my Charger I just installed a QuickFuel 1050 cfm E-85 carb, but it needs a bit of tuning. The 6.5 power valve is too high when the engine only had 5" of vacuum.
I just mentioning the E-85 (105 octane) as an option to the pinging problem.

It's not just the octane- fuel purchased from a pump in the colder months in northern climates has better cold start characteristics than summer blend fuel. It's more volatile, even for the same octane rating.

I'd be interested to see how that e-85 carb works out for you. I see you are from Aurora. I'm at 225 and iliff. I have had the electric choke set all over the place and I do have a spacer on it too. Once it warms up the plugs look clean and it runs pretty good. No stumble or pinging anymore; it's the starting/idle circuit that is killing me. If it doesn't start up easily at first then it quickly fuel fouls the plugs and then won't start without cleaning or replacing the plugs. That is why I'm wondering of the slop in the butterfly shaft is causing problems with the idle circuit transfer slots being exposed at varying amounts. I'm running ngk xr5 plugs. You guys don't think a 950 would be too much for my mild build?

I think the NGK "5" heat range plugs are a hot plug, and should be fine.
I would remove the carb to check how far open the throttle blades are at idle and if they are exposing too much of the transition slot.
It sounds like you have a pretty mild cam, so I don't think it would need a bunch of throttle opening at idle?

I'll send you a PM, You live pretty close by.

Why the heck not?
It's just an engine.

R.