Would like to see if someone has an ideal of what is going on. Last Sunday car ran good for four timetrials then during the first round car popped through the exhaust after shifting out of second gear. Didn't really slow down just popped. Second round no issues. Third round I had just shifted into third when there was a loud explosion from the exhaust. So loud it was heard back at the staring line. I'm leaning toward MSD problems. I have checked the valve adjustment and the valves were loose but I wouldn't think that would cause the backfire through the headers. If it was a broken inner valve spring wouldn't it happen every round and and evertime I reached a particular shift point? Engine is a smallblock stroker with a solid cam. I have also checked to see if the timing moved and checked the cap and rotor on the MSD distributor. Anyone have any ideals on where to look?

Thanks
Gary

ign problem .. ign sw, coil [see how hot its getting] msd last good luck dan

Look for an exhaust leak. This allows fresh, cold air into the exhaust port allowing unburned exhaust gasses to ignite. Blown header gasket, cracked header etc.