SBC Valve spring pressure
I was out today and on the way back my SBC started clacking(rocker arms?) and as soon as I went to an idle it stopped clacking. What it seems to be doing is back firing/missing out the exhaust. I checked the timing/wiring/vacuum leaks and what I have come to the conclusion is that one or more of the exhaust valve springs are getting weak. At idle it purrs like a kitten but at 2000 rpm and up it pops/misses thru the exhaust not the carburetor. If the springs are weak can you compress(move them at all) them a little by hand? It seems to me that the springs are weak. They are very I mean very old. How can you measure spring pressure without taking them to a machine shop?
Thanks - Jerry