Pinging noise at WOT

[dbarron709]

Hi Everyone, I have a 1997 Challenger 800 that I recently brought back to life. and finally got it out for a couple of good days running. On the engine I have replaced the pistons and rings with same size and just cylinder hone to deglaze. I have rebuilt the raves and adjusted them for smooth power. The engine starts, idles and runs great. However, at WOT (7000-7200 rpm) I am hearing a pinging noise. Once I reduce my rpms a bit, it goes away. I have not yet rebuilt the carbs. Would a carb rebuild help? or what would be causing this pinging?

Thanks.

 

[POPPS]

Pinging,,,can be detonation,,,base gasket too thin...too mich compression for the fuel,,.timing curve off,,not retarded enough?,,,what you can try,,,sounds crazy,,,disconnect the in fuel line to the carbs,,at the fuel baffle,,,install an outside fuel container with 93 or 91 octane,,(,highest you can buy,,),to the removed fuel lines,,see if that stops the pinging,,,
You can also double check this theory by removing the head,,,and look for detonation,,,tiny pits around the edge of the piston.

 

[dbarron709]

Finally got out to test again and the 91 Octane (highest I can get in my area) did help. The pinging at WOT is almost completely gone. I do know my carbs need a rebuild as the engine floods after shutdown. Will rebuild carbs next and hope that also helps.

 

[POPPS]

Wonder if the fly wheel is off,(partially sheared),,,,,timing is too advanced?,,twisted crank,,,which can increase timing in the rear cylinder of some 800's,,,flooding,,,sounds like a needle may be sticking?
When my race 800 pings/detonates,,,my fuel does not have enough octane for our compression,,(175),,,but yours is not a modified motor,,,just some ideas,,can you throw in some octane boost to the 91,,,an external container?