3.0 SC Distributor Question
 

What causes timing to driff into retard?

My 1980 SC was running with "lag" and I checked the timing. It must be one of those things that gets worse slowly and then suddenly you realize that it's not right. When I checked it, the timing was at least as far retarded from 5 degrees BTC as the 5 degree mark is from TDC. So it was pretty far out. I adjusted the idle to about 900 RPM and then advanced the distributor to correct the timing. Set it to 5 degrees BTC. The motor now revs with more snap and runs a lot smoother.

What causes it to drift from that setting over time? I assume that it was properly tuned and set when the distributor was rebuilt several years ago and was checked when the motor got a valve adjustment and tune-up about a year ago.

Should I wonder if the advance plate needs servicing?

Idle timing is largely irrelevent. You should check the timing at high rpm to see if it meets the 25 BTDC max advance spec. Both vacuum lines should be disconnectd and plugged. The engine will cold start better and run cooler at idle if you leave the vac retard disconnected and plugged. A distributor is a mechanical device that is subject to wear, but since you do not know what it was set at before, it is hard to make any conclusion. The advance needs to be lubricated by removing the rotor and felt pad and adding a drop or two of oil. Turn the rotor against the spring pressure and feel that it snaps back freely.

Paul

i agree with paul. are you sure it was set properly to begin with?

Thanks. I'll scrounge some tubing that I can use to cover/plug with a golf Tee or something and run it up to see where it goes.

It was running good some time ago. I forget when it started to get bad but it did so very slowly until it was obvious.

I'll oil up the advance. Thanks for the tip. I have excessive blow-by on cyl. #2 and I'm wondering if the exhaust fumes/smoke in the crank case are penetrating the distributor and gumming it up.

Gunter has a great thread on distributor disassembly and cleaning.

its possible, my decel valve and throttle body were full of oil when i removed them. but unlike the decel valve, air does not go through the diaphragms on the dist., but maybe it could run down the hose if there is enough oil.