I have a 69 Chevelle that has been siting for about 2 years becouse I was over seas now I am back and I couldnt get the car to run right I finaly got every thing dialed in but it keeps pinging from 1500 rpm to 2500 rpm under a load after that it stops. I have no vacume leaks I have 38 degrees total timing at 3500 rpm and 8 degrees initial timing (I dont think it is timing I have curved the timing and played with intial timing alot) I rebuilt the carb. the intake has no vacume leakes and it run about 160 to 190 degree F. I have ran 2 tanks of 91 (because thats all they sell localy now) through it and added octane boost and fuel system cleaner? I pulled the motor for paint but every thing is back where it should be. This engine has allway ran great and never given me any problems till now it still runs awsome it just pings alot and loud. :mad:

The engine is as follows: 406 SBC Balanced bluprinted, Brodix street heads, KB pistons 10.2:1 comp, lunati cam 246 in and out at .050 and .515 lift, weind single plane intake, Holly 4160 750 cfm carb, MSD pro-billet dist with 6AL box, Headman shorty headers w/ 3" Flowmaster exhaust. smile.gif

It maybe pulling to much vaccume advance.Pull the vaccume line from the distributor and plug it so you don't have a vaccume leak take it for a spin,see if the problem stops.If this solves you problem you'll have to make a stop to limit how much advance it pulls in.

This may sound stupid, did you change plugs after the car sat? If you did change them were they correct for the heads. You may have put in extended tip plugs when the cylinder heads require short thread plugs, this could but not necessarly cause preignition which can be mistaken for detonation. Just my 2 cents

I did pull the vacume advance and nothing changed I even put safty wire instead of spings on my distributor so I would have no advance except for my initial timing it still ratled and pinged away.

Q-ship I have not even thought about that I will pull a plug in the morning and take a look. I will call Brodix and make sure I am running the correct plugs. Does Pre-ignition and detonation have the same sound or are they different?

Thanks for your input guys!

I took my dad for a ride today and he thinks the pinging sound is too rapid for detonantion is there any thing else that would cause a ratling pingy noise under low rpm's and a load?

I don't think you're getting detonation. You have a pretty big cam relative to the compression ratio along with aluminum heads. Maybe it's something rattling under the dash. Another thought, pretty far fetched though, a U-joint. They can make very strange sounds that are difficult to pin point. Have your dad drive the car while you drive along side. Might help locating the sound.

You may want to take the carb apart and make sure one of your jets are not clogged,or low float setting.You know it's not timing so I would move to fuel could be running lean.