hopefully not another headstud thread
 

recently, my 79 sc has started making a really disconcerting sound. at about 4000rpm to 41/4200rpm the pitch of the engine sound will dramatically change (sounds like the harmonic 5th of the usual note and is very loud). This happens in any gear and even if there is no real load on the engine. i recently replaced the muffler (and gaskets, does not seem to be any leaks but i did not use any rtv on the gaskets) but i have never experienced this effect on any exhaust change up to this point. i will be doing a valve adjust in the next week or two and can check the studs at that point but it does not sound like the dull slapping or rattling sound that i have come to understand is indicative of broken studs. does this sound like something else i could check in the meantime? (sorry if this is somewhat confusing, it's hard to describe a sound)

anyone?

I had a 79 SC that developed a wierd noise at about 4 - 5,000 RPM. Turned out to be a broken inner valve spring, noticed it when I was doing a valve adjustment, I could push the valve in by hand. Luckily the second spring didn't break. I guess you'll be able to check this when you do your valve adjust.

thanks alot. good to know