the 512 in my 72 Challenger is still pinging on me. The motor is a 512 stealth aluminum heads Holley 950 HP carb Comp cams XE295HL-10 cam, 11.3:1 compression, MSD 6Al, MSd Billet distributer, 3,200 Rpm Stall,2"TTI headers, 3" pipe to 3" Flowmaster 40 series , 3:55 gears. Timing is 16 initial 32 total all in by 2,800 RPM. The pinging occurs at about half throttle and it's a pretty loud ping The things I have done to try to solve the problem are

1. Brought the timing down from 34 total to 32 total
2. Upped the primary jets 4 sizes
3. increased the power valve from 2.5 to 3.5
4. Added 5 gallons E85 ( 110 Octane )to 10 gallons of 91 octane
5. went up 2 heat ranges on my plugs


Nothing helped at all I'm at a loss on this problem. Could it be that I'm bringing my timing in too soon? if all of my timing is in at 2,800 and my stall is 3,200 could I be too far advanced when the stall comes in? My engine temps are 185-190 and pretty steady, At this point I'm willing to try anything. I prefer not to tear the motor down but at this point if I need to I will before the pinging tears the motor apart for me.

Looks like you put hotter plugs in it? Need to go the other way. Do you know what your cylinder pressure is? Are the pistons at zero deck or are they down in the hole?

I would think your power valve should be more like 6.5 in gear idle vacuum - 1.5 to 2 numbers.
at light throttle your power valve is staying closed instead of enriching the system the way it is designed.

KILL the motor during the pinging ...and then take a plug-check and "read them".

I'll have to check my Idle vacuum again but I think I have 9" at idle in gear Holley recommended the 2.5 power valve. Somebody suggested that it might be a lean ping but going up 4 jet sizes didn't help at all. I went to a hotter plug because I fouled one when the motor was still pretty new.I will change to a colder plug in the morning and see if that helps.

I don't know what my cylinder pressure is I can check it while I have my plugs out tomorrow I think they are zero deck the motor was designed to be 11.3:1

Try a 160 degree thermostat.

What is your cranking cylinder pressures?

I don't know my Cranking pressures. Maybe that's why I can't solve this problem I don't know the important info like pressures and piston height

Just a couple of thoughts here..You are at 0 deck and don't know piston heighth...You may be at more than 11.4-1 compression..What kind of pistons and what is the cylinder head ccs...Lots of stuff to look into...Wouldn't want to see you hurt that engine!! Here is a pic of my 13.4-1 512..

Put a compression tester on it and find out what it's cranking. E85 is not what you need to increase pump premium's octane. To effectively increase your octane, try running some % of 100 octane unleaded or add 110 octane leaded to your tank. You will have to rejet no matter what you do when you start blending your fuel, so be consistent with the mixture once you get a ratio that works. You may want to get a knock sensor to detect detonation and a wideband with data logger. FAST has a nice wideband unit.

I only drive my car for fun and rarely burn more than a tankful a month, so I intentionally opted for high compression (12.8 to 1 @ 225psi cranking). I've always liked how it runs with it, and I don't really care about the cost difference to run high compression because of the performance trade off. I don't drive the car that much. Also, I know you can't get 100 octane unleaded everywhere, so I had a larger tank made to extend my cruising range.

I do have to pay about 1/2 again more for each gallon of the fuel to meet the octane requirements. I was going to mix 110 octane unleaded, but that's illegal in California now. Fortunately, my motor likes the 100 octane unleaded at about $6.50 a gallon.....and rising, but I knew this going in. Sounds like you didn't know your compression is too high for normal pump gas.

If she is pinging drain the tank and fill with racing gas; not a mixture. If that stops the pinging then play with mixtures and the like but don't mess up a good build playing with detonation. There are too many unknown varibles and you can get lost in the testing game without first feeding your motor a quality fuel.

E-85 + 91, might as well put 87 octane in it . I have a 493-0 deck-84cc milled to74cc,runs on 93 octane .

Like what a few guys have already said, get rid of that swill gas you have now, and put some real gas in it.
I'm betting the compression is higher than you think. 0 deck? I would have CC the engine after I had the heads on, when I put it togeather so I knew for sure what the compression is.

Get good gas first. Like what already said, I'd start with a straight 110 leaded. You maybe be able to blend down from there, but at 11+-1 gonna need more than prem pump gas. Hopefully you have someone nearby who sells race gas at the pump or buy it by the drum. Speed and horsepower cost $$

We have a place nearby that sells 100 octane unleaded and 110 leaded at the pump, makes it nice.

I don't drive the car much when I bought the motor I also knew the compression was high for the street but didn't care. The car has been done for almost 1- 1/2 years and it has less than 1,000 miles on it. I was driving it last night and it pinged on me a couple times. I drove by a gas station that sold E85 and thought I would try it to see if it helped but it didn't. It's raining here but as soon as it stops I will get cranking pressures and put the colder plugs in it. I got the RJ12YC plugs that 440 source recommended for the motor and I'll try them.

I would think with that high of compression you would need a colder plug than that! And I read in mopar muscle that in order to use E85 you need to switch parts of your fuel system such as the rubber needles in your carb. The rubber are the things that E85 will deteriorate over time. I could be wrong! Anyone read that issue from 4-6 months ago? it was the one guy's Valiant that they did it to.

I will get the corn gas out of it. I forgot about it eating the rubber in the fuel system. I have a Phillips 66 about a mile from my house that sells straight gas no ethanol I'll get some. I can't get any race gas until Monday unless somebody is on here from Boise and Knows where to get it on a Saturday.