kwf Posted January 24, 2011 Share Posted January 24, 2011 I am trying to find out if the valves on a 1947 707A mack engine head are recessed in the head or if the head is flat. I think the timing chain may have broken and wonder if the pistons could have hit the valves. Quote Link to comment https://www.bigmacktrucks.com/topic/17692-707a-mack-engine-head/ Share on other sites More sharing options...
bullhusk Posted January 24, 2011 Share Posted January 24, 2011 I don't thing there is a timing chain in a 707 they use timing gears. It could have a stripped or broken gear, just pull your dist. cap off an turn the motor over, if the dist. shaft don't turn then you prob. have a timing gear prob. Quote Link to comment https://www.bigmacktrucks.com/topic/17692-707a-mack-engine-head/#findComment-71524 Share on other sites More sharing options...
fxfymn Posted January 25, 2011 Share Posted January 25, 2011 I am trying to find out if the valves on a 1947 707A mack engine head are recessed in the head or if the head is flat. I think the timing chain may have broken and wonder if the pistons could have hit the valves.Is the motor stuck? Quote Money, sex, and fire; everybody thinks everyone else is getting more than they are! Link to comment https://www.bigmacktrucks.com/topic/17692-707a-mack-engine-head/#findComment-71588 Share on other sites More sharing options...
kwf Posted January 25, 2011 Author Share Posted January 25, 2011 Is the motor stuck? No the motor is not froze up. It will turn over by hand or the starter. It was running and made a pop and was shut down. I am thinking and hope that one of the timoing gears may have broken or maybe a keyway may have sheared off. Has anyone experienced a similar problem with the 707A engine. Quote Link to comment https://www.bigmacktrucks.com/topic/17692-707a-mack-engine-head/#findComment-71598 Share on other sites More sharing options...
fxfymn Posted January 27, 2011 Share Posted January 27, 2011 I assume it will not run on either ignition system. Am I correct? Have you tried starting it on Ignition 1 and/or Ignition 2 instead of Both?Is there any metalic sound coming from the timing gear cover? Can you hear the engine "lope" or backfire when you try to start it? Either indicate timing problems.Is the distributor rotor moving when you crank the engine over? If so align the mark on the dampner that is used to time the engine with the indicator on the housing and see if the rotor is pointing to the number 1 cylinder position of the distributor cap. If not, it may be 180 degrees off. In that case rotate the engine once to bring the timing mark back into position again. Re-check the rotor position.If the rotor does not point to the number one cylinder something has gone amiss with either the distributor drive or the timing gear. Can the distributor rotor be moved by hand? If so the distributor drive is probably broken. Pull the distributor to check it.Did you shut the engine down or did it quit? A "pop" could be caused by lack of fuel that resulted in a lean condition which in turn led to a "backfire" sound. Is there fuel at the carb.?It's really hard to troubleshoot a problem without a complete description of what happened and what it is doing now. However, I have found that most of the time the big expensive stuff jumps right out at you; otherwise it's usually something simple that you overlook because you are so sure that something major has gone wrong. Quote Money, sex, and fire; everybody thinks everyone else is getting more than they are! Link to comment https://www.bigmacktrucks.com/topic/17692-707a-mack-engine-head/#findComment-71707 Share on other sites More sharing options...
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