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Thomas Fournier

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Ok I have a 350 SBC, bored 20 over eagle rods and balanced, 68cc performance iron heads w/ ARP studs edelbrock intake, crower beast cam full roller comp iron rockers, Sean Murphy quadrajet, Chevy H.E.I. w/ Accel coil and module w/ msd cap and rotor w/a recurve kit for 32 degree advance at 3200rpm. It pings like crazy even just light throttle. What am I doing wrong. It's set at 8 degrees primary and even w/the vacuum advance not hooked up it still pings. Yes it's on premium shell 91 octane. And the engine was built by a local reputable shop. Any input would be great cause I'm starting to just give up!

Thanks,
-Daniel
 

ChrisPerry

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Confirm the timing marks are correct using a piston stop.
 

Joe In Montana

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Ok I have a 350 SBC, bored 20 over eagle rods and balanced, 68cc performance iron heads w/ ARP studs edelbrock intake, crower beast cam full roller comp iron rockers, Sean Murphy quadrajet, Chevy H.E.I. w/ Accel coil and module w/ msd cap and rotor w/a recurve kit for 32 degree advance at 3200rpm. It pings like crazy even just light throttle. What am I doing wrong. It's set at 8 degrees primary and even w/the vacuum advance not hooked up it still pings. Yes it's on premium shell 91 octane. And the engine was built by a local reputable shop. Any input would be great cause I'm starting to just give up!

Thanks,
-Daniel


Causes for 'pinging' --->
  • Lean fuel mixture. [also lack of- or short- accelerator pump adjustment or action; low float level, no emulsion tubes (carbs)].
  • Over advanced timing - [you state it's not your problem].
  • Vacuum leaks - [usually worse at idle or 'tip-off' though].
  • Supercharger pop off set at 65# [or higher].
  • Over advanced cam - [did someone misinterpret the cam gear timing marks?].
  • Compression too high. [Pistons with high domes and an intrusion design, small cc heads, etc.]
  • Marbles in the combustion chamber(s)
  • Lack of EGR - [which cools the charge and prevents knocking/pinging].
  • Wrong heat range spark plugs - [are you using Champions? I dislike them intensely].
  • Low octane [I included this although you state it's NOT your problem].
  • Low coolant level; wrong thermostat [not likely these days - I use a 200F for my '86 383 stroker].
  • Bad/defective/missing/poorly working fan clutch or electric fan(s).
  • Low altitude - [carbs are not usually computer/mixture controlled for changes in altitude].
  • Intake valve(s) adjusted too tight and holding the valve slightly open all the time..

I know that if I take my 6000 foot altitude engines to sea level - they ping and knock badly.
If you left any of the computer in the system still, it should 'hear' the engine ping and start retarding the timing..
 

1-ton

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Connect vacuum gauge to manifold vacuum, then turn distributor to max vacuum inch...then back off 1-inch, and test drive. make sure the distributor is hooked up to manifold vacuum and not port vacuum.
 
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