 tractorboy wrote:
I bought a timing light,I was close by ear, but it looks like it is not firing at the same place I'm warmed up & pretty much wide open during this check. Should the mark be rock steady when it fires?? Yes the dist. has slack in it but so do my other 6 AC's they all run like a swiss watch. The dist shaft has no wobble just a lot of back-lash. |
A bad condenser, weak point spring, or weak valve would all be appropriate suspects, as would be a tiny crack or leak in an exhaust manifold, but what you've noted is the best clue here... you're not getting a steady ignition event. Weak point spring, bad condenser, and dirty points would be my first, simply becausue they're quick and easy.
The Delco-Remy distributor in the Allis engine develops slop, and as you noted, usually in the radial plane, and this slop means that the point cam's lift point is directly affected. Radial slop means the cam lifts the points inconsistently, AND, the ignition dwell time is wrong, which at high speed, can cause a really blatant miss.
Vertical motion may not SEEM like it can cause timing issues, but the timing gears below will cause the shaft to kick around, again causing an unstable event... See the gears on the bottom of the distributor? if it's walking vertically, your timing will change.
As Mack noted, the governor gear may also be worn... look at how the distributor drive works- from the governor housing, a horizontal shaft driven by governor gear, to a 90 degree worm (rather than bevel) drive. When ANY of these gears exhibit slop, the result is opportunity to affect timing event stability.
IF the governor gear is good, drive out the crosspin, remove the distributor drive gear, and install a thin washer or three between gear and housing, to take up the vertical slop, then reinstall gear and crosspin, reinstall, set timing, and try again.
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Another thing to note... how BAD is this occasional 'pop'?
Many do not realize that running at high idle (meaning, full governed speed) with no load, includes a little popping. Why? Because the engine is spinning fast, the cylinders want to fill completely, but the governor is restricting the flow of fuel. Why? Because there's NO LOAD... the throttle, being closed, is limiting fuel, thus, it's pretty darned lean in that chamber.
It wasn't designed to be a smooth running engine at full speed, while doing no work... it was designed to be smooth and efficient under a HEAVY load... so, Put a load on it... make it work. Does it still pop? If so, then explore the situation. If not, call it normal.
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