Pinging at low total timing advance

[SmudgeServices]

440-6 bored .30 over, compression is over 10:1, maybe 10.25:1. Lunati Voodoo cam 10230702 but mainly stock beyond that.

car was running hot at idle so i checked the initial timing and it read only 3 degrees BTDC! definitely doesn't help the temperature. Vacuum advance disconnected.
i wanted to bump it up into the 16-20 degree range for responsiveness, temperature, etc.
in exploring this i quickly bumped it up to 10 degrees advanced and went for a drive but she started pinging like crazy -- too far advanced. puzzled me because it still seems lower than it should handle.

so i read up that 34 degrees Total Timing is a reliable goal to hit. i was able to set the total timing at 34 degrees, with no vacuum advance, at 2800-3000 rpms. initial was ~10. went for a drive and it was still pinging like mad.
i retarded the timing a smidge and went for a drive again, still pinging but less. repeated this a few times until pinging was completely gone.
then i checked the timing again to see where it was at since this is obviously my max timing advance. sure enough, initial is back at 3 degrees and total is at 26 degrees advance. (again- no vacuum advance, 2800-3000 rpms).

pinging occurred when i kicked into it for this entire scenario. never when i was putting around the neighborhood or running less than 2000 rpms.

i purchased an FBO Limiter plate so i'm going to pull the distributor out this week and put it on a limit of 10 degrees to advance, then set the initial at 16 degrees and live with the most initial i can get out without pinging.

so i'm wondering if this is a real problem?
what could be causing the pinging at such a low advance?
it definitely doesn't feel right.

 

[Chryco Psycho]

You may actually want to extend the curve not shorten it so you can run around 5* at idle & 34-36* total . Connecting the vacuum advance to ported vacuum could help also to add higher rpm timing .
Other factors are spark plugs too hot , mixture too lean , possible carbon build up or oil contamination . If you think of it as a oxy acet torch less fuel /acet increases temp , more fuel/ acet cools temps . A water / acohol inj system can help also .
I assume you have 906/346/452 heads so you have no quench , closed chamber heads using quench will help kill detonation even if the compression ratio is increased .

 

[Xcudame]

You're right on the cusp for iron heads, pump gas and detonation. I'd try an octane booster just to see if the pinging stops. Then you have several choices which include tweaks Chryco Physco is suggesting, a thicker head gasket, or continuing to use octane booster.

 

[1972 AAR Cuda]

I would also check the timing mark - I have seen vibration dampeners slip and the timing mark moves with it. You didnt mention the condition of the motor (rebuilt?). Is the dampener used or reused? I would really wonder if the timing your showing is accurate.

 

[Deathproofcuda]

You're right on the cusp for iron heads, pump gas and detonation. I'd try an octane booster just to see if the pinging stops. Then you have several choices which include tweaks Chryco Physco is suggesting, a thicker head gasket, or continuing to use octane booster.

I agree with Xcudame. You never stated what kind of gas you are running on, but I'd start with the cheap and easy checks like an octane booster before I'd start tearing into anything mechanically. 10.25:1 is pushing the limits for running pump gas, especially if you are running open chamber heads. My buddy is buying small drums of Sunoco racing gas to bump the octane for his GTO.

 

[SmudgeServices]

I always run 93 octane (it's the highest available locally and conveniently) with the minimal ethanol possible (which is usually 5 or 10%). I'll give some octane booster a try

 

[Katfish]

My old 340 could never take more the 26 total without pinging.
Stock X-heads and compression, and I'm in FL, so its hot.
I ended up with 10-12 initial and a FBO limiting plate for 26 total.
I think everything has to be perfect to get to that 34 number everyone strives for.

 

[moparleo]

Before you start doing a bunch of guesswork. You always should start at the beginning.
Question, are you the original engine owner ? Can you personally verify the build parts or just someone told you this ?
Diagnostics always require a baseline.
Did the car ever run properly ? New build ? Cooling system specs. Ignition type ? Verified true TDC with the Balancer that is installed ?
More info is needed.
Factory specs for 1970 440+6
CR. - 10.5:1 110 psi
Base timing 5° - plus or minus 2-1/2°
Spark plugs - Champion J-11Y or J-10Y

 

[Cratos]

I got tired of all the crappie fuel (only run Non eth) so i stared adding vp octane booster. 1.5 oz to 5 gall no more pinging i can only get 89 NE fuel around here so I had to do something!!

 

[Cratos]

well with summer here now.I had to resort to 50/50 mix of 100LL av gas and 90 rec ( non eth) even with the octane buster was not cutting it.
all happy now,

 

[heminut]

well with summer here now.I had to resort to 50/50 mix of 100LL av gas and 90 rec ( non eth) even with the octane buster was not cutting it.
all happy now,

Av gas was a staple for us back in the day when premium gas went away and unleaded was introduced.