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broken rockers?

I got half a dozen calls in one day over broken rocker arms. Customers break rockers and they call for more rockers but the problem is that rockers don't just break. There's ALWAYS a reason why it broke. If that reason doesn't get addressed, you will continue to break one rocker after another, and potentially bend valves and cause other related damage. If you're only breaking intake rockers, odds are, the engine was ran with old gas. If pushrods were replaced with stronger units, the next path of least resistance for breakage if the valve sticks in the guide is the rocker. Bad gas is like glue. i bring that up in quite a few of these articles. i can't emphasis enough, the seriousness of running old gas. All it takes is a gallon to contaminate an entire fresh tank of gas, and the entire tank needs to be drained and cleaned. Running high octane is irrelevant. how "old" is old gas? it depends on a lot of variables. You can tell by the way it smells, typically. Anything over a year starts to get concerning. Gas starts breaking down in only a handful of months. The more ethanal content, the shorter the lifespan. Ethanal is used to boost octane levels. So despite what people may think, higher octane has/may have a shorter lifespan than the latter. Gas, stored in sealed containers lasts longer in theory. If only exhaust rockers are breaking, it's usually right after a valve job and its an indication that the guide clearance is likely too tight! You need .003-.0035 on exhaust valves (.002-0025 on intake) People set them up at .0015 on exhaust and they are guaranteed to lock up. May not happen immediately. Sometimes you can put thousands of miles on before failure, then the rockers start breaking one after another after stem galling. If both intake and exhaust are breaking, then explore coil bind. Wrong outer spring shims can interfere with the inner springs if ID is too small. Too much lift is easy to have with 58 and earlier valves with shorter (.100" less) spring install height. If you break both on the same cylinder, it could still be too tight of guide clearance. If exhaust rocker breaks, then intake can't open because the cylinder is still under pressure, therefore breaking the intake rocker as well. But from my experience, it's never the rockers' fault. #



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