Pinging Question?

[Justins72]

From what i have read that pinging or detonation genrealy occurs during low rpms, but thats the problem when its from mid to high rpms? the car is a 340, cam, ported and polished heads, edel manifold, 750cfm carb. not sure what the CR is, so any sugestions? im running the highest octane in california wich 91. Should i put ocane boost in as well, get a colder spark plug, or use both.                          Thanks

[MEK-Dangerfield]

Welcome aboard Justin. 

  To answer your question, it would help to know the compression ratio. 91 octane isn't helping you out here. I have no experience with octane boosters, but that would be great if you could get that to do the trick. Have you tried retarding the timing a few degrees? Take a look at the spark plugs too... you might be running lean.

  Mike

[todd383]

Or just switch to a colder plug will help too.

[kudakidd]

Justin, welcome to CC.Com. Pinging can occur at any rpm. It usually is caused by incorrect ignition timing, but also can be caused by carbon deposits, wrong heat range spark plugs or an overly lean carb setting.

[Justins72]

ok well i went out today and pulled the plugs but didnt relize that they are this platinum plugs which clean themselves supposidly, but from what my neighbors tell me that it smells like its running rich. i checked the timming also which was at 45 degrees advanced at 3000 rpm, is that too much? i have lowered it but the car wouldnt start then.  I have a compression tester is there a way to tell the CR from the psi each cylinder gives?   Also would a local auto parts store sell colder spark plugs?                                                                                Thanks

[Chryco Psycho]

I would start with changing the plugs , I use Champion RN14YC   gapped at .040-.045
 never been a fan of the platinum spark plugs
 if the engine has a cam in it it can smeel rich at idle & stil be set lean
 I deally you want 36-38* at 3000 RPM but ithe damper could be in the wrong position  , or the curve could be too long& you do not have enough advance at idle , you can try either disconnecting the vacuum advance completely & not using it at all or inserting an allen wrench into the hose nipple on the vacuum pot & trunin git counterclockwise 8 turns or so to shorten the curve
 you can get an approximate comp ratio with a compression guage  But cam profile can drop the reading significantly at cranking speed   

[Justins72]

since it finaly stopped raining i got back to work on the challenger i complety disconnected the distributer vacuum advance. the timing is at 38 degrees advanced and i gapped the plugs i have now to  .045 like suggested and took the car out for a little test drive and i still have that horrable pinging sound. So now the only other option i got to do is get a colder plug. Anyone have a suggestion on which one to get? how cold should it be? If that doesnt work then i dont know what im going to do.

[Chryco Psycho]

you may need to back the timing off to 34 * & or run better fuel , colder plugs may help as well

[Justins72]

some good news is that i got the car running much better then it was. I adjusted the carb some more and notice that the carb bolts was getting loose tighten it down set the timing to 36 degrees and now there seem to be no pinging for now and i was getting on it all day so hopefully this was the problem and i can now move onto other things.

[MEK-Dangerfield]

Wow, that's great news!!!  I'm sure if you could get 93 octane gas out there, you would have no problems. I hope you have it solved. 

  Mike

[Oldschool]

This is the real deal.  Might help your octane situation at a fair price. A little goes a long way.  http://www.kemcooil.com/product_info.php?pId=61     Hope it helps.         ....Oldschool

[pink panther]

I have to use octane booster in my car 340 big cam  3 two barrells. pump gas just isn't enough.  you can definatley feel the difference when not using booster.   Chryco can get you right though.  If you got the money even Orielly auto partssells race fuel in 5 gallon increments, or you can go to the track and get some.  It would tell you if the octane in your fuel is the problem.   
Quick question:  have you recently change oil?  some motors don't sound quite right with a lighter iol in them.

just my thoughts.

[Chryco Psycho]

a vacuum laek can lean the engine & increase heat causing pinging so yes you may have solved the problem