Here's the story - I built a 383 for my 1972 C10 pickup. The plan was for a torquey engine with a stable idle for this heavy truck. Basic specs are as follows; AFR aluminum heads with 195CC intake runners/64cc chambers KB pistons with 18cc dish (I make this combination to be about 9.7/1 Comp ratio) Howards cam @.050 lift; In duration 215 Ex duration 225 In lift .455 Ex lift .465 Lobe separation 112 degrees New HEI distributor from DUI - has a nice smooth 24 degrees of mechanical adv. I can't get it to not ping under acceleration, even fairly light acceleration, as well as lugging the starter when hot. I'm down to 4 degrees BTDC on static timing and it still pings but starts reasonably well. Any slower and it runs too rough and the power falls way off. I've also tried heavier advance weight springs to slow down the advance curve but with little effect. I'm running with no vacuum advance also. I've built a few small blocks in the past but not for 20 years or so, and this is the first 383 for me. I've worked on all the ignition timing tricks I know and have searched thread after thread to look for some hints as far as what I may be missing here. Most of the recommendations I see are for something around 12 BTDC static. No way I can get close to that with this engine. I'm wondering if I need a more aggressive cam for this compression ration? Any help from the experts will be greatly appreciated.