The Stovebolt Site Forums The Shop Area Engine Shop ign/ timing prob on '48 GM flathead 6

fellas,

It's not a stovebolt, but a great old GM flathead 6 and I need help! I was driving my 1948 Olds with flathead 6, and it just quit on me. Was running great. I've ruled out fuel and spark. I'm wondering if the timing slipped? When I pop the dist. cap I can move the rotor maybe 40 degrees by hand, enough to fully open and close the points. The clamp bolt on the dizzy is tight. Could the dizzy be moving on the inside? Could I have a worn out timing gear/ chain? I'm really baffled here because it was running so sweet and then just quit on me. Any help from the stovebolt gurus would be appreciated!
Regards,
Tyler

Start with having some twist the key and see if the rotor spins about. What about the points? Do they still open and close? Can you pull a spark plug out and hold against the block while some one cranks the thing to see the spark? Did you try a timing light on it?

The engine has probably a centrifigal advance with weights and springs and those weights swing out and retard the spark to make the engine run right at higher RPM. You should feel tension against the rotor when you twist it. If not, then perhaps the spring has broken or slipped off?

If you have a strobe see if the timing is going. If not hook a light bulb to 2 wires and put one on the points and the other on ground. As you rotate the engine with a breaker bar see if the light goes on and off which tell you that the ignition system has power and that the points are opening and closing.

Do you smell fuel in the carb?

If you've ruled out fuel and spark (ignoring all my 'sage' advice) then is the cam still turning and do you have compression?

OK, figured out the prob here. Took the dist. cap off and tried moving rotor by hand. Rotor had close to 90 deg. of play! I realized that it had to be losing timing because the rotor was jumping around. So I pulled the dizzy, but it looked OK. Then I dropped the (externally mounted) oil pump to see if there was something broken in the slot that drives the dist. Turns out what turns the tang on the bottom of the dist. shaft (thereby driving the distributor) is 4 thin pieces of sheet metal that fit into slots on the end of the oil pump shaft. These were quite bent, so while the oil pump would still turn the dist., there was some slip-sliding going on; i.e. when the tang on the dist. would slip against the drive pieces of sheet metal, it would throw the rotor off by probably 60-80 degrees and thus kill the timing. I don't know exactly what the best way to cure this problem would be- I straightened out the little pieces of sheetmetal, but I'm worried that eventually they'll just bend again and maybe even break? Maybe I'll replace them with something more stout. Thanks for the reply, Arnswine.

Could the dist be hanging up like shaft not getting any lube or something catching & twisting the drive mech. Could this be a patch up job from a previous owner?