[pmead]

I just started car and checked exhaust temps at each exhaust flange and they are all close to the same. No obvious cylinder not firing. I blocked the exhaust with a rag momentarily to check for exhaust leak, no change in sound. Tomorrow I will start with plugs and then check compression or pull valve covers. Would a broken valve spring create this problem? I do not get any smoke. It sounds more like a small exhaust backfire and is in rhythm with the rpms. What are the symptoms of broken head studs?